Ole Martin Løvvik

• Rahman, Jamil Ur; Soltani, Nayereh; Sunding, Martin Fleissner; Løvvik, Ole Martin; Gunnæs, Anette Eleonora & Finstad, Terje Gunnar [Vis alle 7 forfattere av denne artikkelen] (2024). Deciphering the structure of a high entropy Heusler antimonide. Acta Materialia. ISSN 1359-6454.
• Amundsen, Monika; Pike, Nicholas; Løvvik, Ole Martin; Almeida Carvalho, Patricia & Gunnæs, Anette Eleonora (2022). New structure and insight on the phase transition within the Cu-Pd-Sn system with 25 at. % Sn. Materialia. ISSN 2589-1529. 24, s. 1–6. doi: 10.1016/j.mtla.2022.101461. Fulltekst i vitenarkiv
• Tranås, Rasmus André; Løvvik, Ole Martin & Berland, Kristian (2022). Attaining Low Lattice Thermal Conductivity in Half-Heusler Sublattice Solid Solutions: Which Substitution Site Is Most Effective? Electronic Materials. 3(1), s. 1–14. doi: 10.3390/electronicmat3010001. Fulltekst i vitenarkiv
• Mayandi, Jeyanthinath; Finstad, Terje Gunnar; Dahl, Øystein; Ponniah, Vajeeston; Schrade, Matthias & Løvvik, Ole Martin [Vis alle 8 forfattere av denne artikkelen] (2022). Thin films made by reactive sputtering of high entropy alloy FeCoNiCuGe: Optical, electrical and structural properties. Thin Solid Films. ISSN 0040-6090. 744(139083). doi: 10.1016/j.tsf.2022.139083. Fulltekst i vitenarkiv
• Bazioti, Kalliopi; Løvvik, Ole Martin; Poulia, Anthoula; Almeida Carvalho, Patricia; S. Azar, Amin & Mikheenko, Pavlo [Vis alle 8 forfattere av denne artikkelen] (2022). Probing the structural evolution and its impact on magnetic properties of FeCoNi(AlMn)x high-entropy alloy at the nanoscale. Journal of Alloys and Compounds. ISSN 0925-8388. 910, s. 1–12. doi: 10.1016/j.jallcom.2022.164724. Fulltekst i vitenarkiv Vis sammendrag

  We report the first nanoscale investigation of FeCoNi(AlMn)x high-entropy alloys (HEAs) processed by laser metal deposition. The structural evolution of the alloy upon chemical composition variation (0.2 ≤ x ≤ 1.5) was investigated by combining imaging and spectroscopies in (scanning) transmission electron microscopy (S)TEM with density functional theory (DFT). A gradual change from a face-centered cubic (FCC) towards an ordered full-Heusler (L21) phase by increasing the Al and Mn contents was observed. Direct imaging and atomic-scale calculations revealed a nanoscale interplay between B2 and L21 ordered structures for x = 1.5, wherein the latter, Al and Mn occupy two different Wyckoff sites. By decreasing x, the FCC phase dominates exhibiting intense phase separation tendency, ordering phenomena, and nano-precipitation. Although not chemically discriminated, plasmon-peak splitting in low-loss electron energy loss spectra revealed the presence of two valence electron densities within the FCC phase. Lorentz TEM showed that the ordered nano-precipitates and nano-sized grains with a structure based on a tripled FCC unit cell are pinning-sites for magnetic domain walls and dislocations. All alloy compositions exhibited soft-magnetic behavior with coercivity (Hc) values< 1000 A/m. The FeCoNi(AlMn)1.5 alloy with L21/B2 nanostructure showed the highest magnetization (Ms) with relatively low Hc, attributed to the large magnetic moment of Mn and the synergistic effect of Mn-Al according to DFT, whilst ordering does not impose a negative effect. Phase separation trends within the FCC phase seem to decrease the Ms however, the overall impact on the magnetic behavior is not intense, opening up for new avenues for tuning FeCoNiAlMn properties through chemically-designed phase decomposition regimes.

• Mayandi, Jeyanthinath; Schrade, Matthias; Ponniah, Vajeeston; Stange, Marit Synnøve Sæverud; Lind, Anna Maria & Sunding, Martin Fleissner [Vis alle 13 forfattere av denne artikkelen] (2022). High entropy alloy CrFeNiCoCu sputter deposited films: Structure, electrical properties, and oxidation. Journal of Vacuum Science & Technology. A. Vacuum, Surfaces, and Films. ISSN 0734-2101. 40. doi: 10.1116/6.0001394. Fulltekst i vitenarkiv Vis sammendrag

  High entropy alloy (HEA) films of CrFeCoNiCu were deposited by sputtering. Their structure was characterized and their electric transport properties were studied by temperature-dependent Hall and Seebeck measurements. The HEA films show a solid solution with an fcc structure. The residual electrical resistivity of the films is around 130 μΩ cm, which is higher than the Mott limit for a metal while the temperature dependence of the resistivity above 30 K is metal-like but with a small temperature coefficient of resistivity (2 ppm/K). The dominant scattering mechanism of charge carriers is alloy scattering due to chemical disorder in the HEA. The Hall coefficient is positive while the Seebeck coefficient is negative. This is interpreted as arising from an electronic structure where the Fermi level passes through band states having both holes and electrons as indicated by band structure calculations. Below 30 K, the conduction is discussed in terms of weak localization and Kondo effects. The HEA structure appears stable for annealing in vacuum, while annealing in an oxygen-containing atmosphere causes the surface to oxidize and grow a Cr-rich oxide on the surface. This is then accompanied by demixing of the HEA solid solution and a decrease in the effective resistance of the film.

• Amici, Julia; Asinari, Pietro; Ayerbe, Elixabete; Barboux, Philippe; Bayle-Guillemaud, Pascale & Behm, R. Juergen [Vis alle 49 forfattere av denne artikkelen] (2022). A Roadmap for Transforming Research to Invent the Batteries of the Future Designed within the European Large Scale Research Initiative BATTERY 2030+. Advanced Energy Materials. ISSN 1614-6832. 12. doi: 10.1002/aenm.202102785. Fulltekst i vitenarkiv Vis sammendrag

  This roadmap presents the transformational research ideas proposed by “BATTERY 2030+,” the European large-scale research initiative for future battery chemistries. A “chemistry-neutral” roadmap to advance battery research, particularly at low technology readiness levels, is outlined, with a time horizon of more than ten years. The roadmap is centered around six themes: 1) accelerated materials discovery platform, 2) battery interface genome, with the integration of smart functionalities such as 3) sensing and 4) self-healing processes. Beyond chemistry related aspects also include crosscutting research regarding 5) manufacturability and 6) recyclability. This roadmap should be seen as an enabling complement to the global battery roadmaps which focus on expected ultrahigh battery performance, especially for the future of transport. Batteries are used in many applications and are considered to be one technology necessary to reach the climate goals. Currently the market is dominated by lithium-ion batteries, which perform well, but despite new generations coming in the near future, they will soon approach their performance limits. Without major breakthroughs, battery performance and production requirements will not be sufficient to enable the building of a climate-neutral society. Through this “chemistry neutral” approach a generic toolbox transforming the way batteries are developed, designed and manufactured, will be created. © 2022 The Authors. Advanced Energy Materials published by Wiley-VCH GmbH

• Mayandi, Jeyanthinath; Finstad, Terje Gunnar; Stange, Marit Synnøve Sæverud; Vasquez, Geraldo Cristian; Sunding, Martin Fleissner & Løvvik, Ole Martin [Vis alle 8 forfattere av denne artikkelen] (2021). Controlling the Electrical Properties of Reactively Sputtered High Entropy Alloy CrFeNiCoCu Films. Journal of Electronic Materials. ISSN 0361-5235. 51, s. 803–812 . doi: 10.1007/s11664-021-09343-3. Fulltekst i vitenarkiv Vis sammendrag

  Oxide-containing films were made by reactively sputtering a high-entropy alloy target of CrFeCoNiCu. We report on a wide range of changes to the electrical properties made by different heat treatments in oxidizing and reducing atmospheres, respectively. We combine temperature-dependent Hall effect measurements down to 10 K to study the transport mechanisms and correlate that with structural measurements by x-ray diffraction and scanning electron microscopy. The measured/effective resistivity could be varied between 1.3 × 10−4 Ω cm and 1.2 × 10−3 Ω cm by post-deposition processing. The temperature coefficient of resistivity could be varied between − 1.2 × 10−3 K−1 through 0 and to + 0.7 × 10−3 K−1. The key to the variation is controlling the morphology and topology of the film. The conduction of charge carriers is dominated by the relative contribution of weak localization and alloy scattering by varying the degree of disorder in the metallic high-entropy alloy and its topology.

• Tranås, Rasmus André; Løvvik, Ole Martin; Tomic, Oliver & Berland, Kristian (2021). Lattice thermal conductivity of half-Heuslers with density functional theory and machine learning: Enhancing predictivity by active sampling with principal component analysis. Computational Materials Science. ISSN 0927-0256. 202. doi: 10.1016/j.commatsci.2021.110938. Fulltekst i vitenarkiv Vis sammendrag

  Low lattice thermal conductivity is essential for high thermoelectric performance of a material. Lattice thermal conductivity is often computed using density functional theory (DFT), typically at a high computational cost. Training machine learning models to predict lattice thermal conductivity could offer an effective procedure to identify low lattice thermal conductivity compounds. However, in doing so, we must face the fact that such compounds can be quite rare and distinct from those in a typical training set. This distinctness can be problematic as standard machine learning methods are inaccurate when predicting properties of compounds with features differing significantly from those in the training set. By computing the lattice thermal conductivity of 122 half-Heusler compounds, using the temperature-dependent effective potential method, we generate a data set to explore this issue. We first show how random forest regression can fail to identify low lattice thermal conductivity compounds with random selection of training data. Next, we show how active selection of training data using feature and principal component analysis can be used to improve model performance and the ability to identify low lattice thermal conductivity compounds. Lastly, we find that active learning without the use of DFT-based features can be viable as a quicker way of selecting samples.

• Berland, Kristian; Løvvik, Ole Martin & Tranås, Rasmus André (2021). Discarded gems: Thermoelectric performance of materials with band gap emerging at the hybrid-functional level. Applied Physics Letters. ISSN 0003-6951. 119(8). doi: 10.1063/5.0058685. Fulltekst i vitenarkiv Vis sammendrag

  A finite electronic band gap is a standard filter in high-throughput screening of materials using density functional theory (DFT). However, because of the systematic underestimation of band gaps in standard DFT approximations, a number of compounds may be incorrectly predicted metallic. In a more accurate treatment, such materials may instead appear as low band gap materials and could have good thermoelectric properties if suitable doping is feasible. To explore this possibility, we performed hybrid functional calculations on 1093 cubic materials listed in the MATERIALS PROJECT database with four atoms in the primitive unit cell, spin-neutral ground state, and a formation energy within 0.3 eV of the convex hull. Out of these materials, we identified eight compounds for which a finite band gap emerges. Evaluating electronic and thermal transport properties of these compounds, we found the compositions MgSc2Hg and Li2CaSi to exhibit promising thermoelectric properties. These findings underline the potential of reassessing band gaps and band structures of compounds to identify additional potential thermoelectric materials.

• Bernal, Fabian Leonardo Martinez; Lundvall, Fredrik; Kumar, Susmit; Hansen, Per-Anders S.; Wragg, David S. & Fjellvåg, Helmer [Vis alle 7 forfattere av denne artikkelen] (2021). Jahn-Teller active fluoroperovskites ACrF3 (A=Na+, K+): Magnetic and thermo-optical properties. PHYSICAL REVIEW MATERIALS. ISSN 2475-9953. 5(6). doi: 10.1103/PhysRevMaterials.5.064420. Fulltekst i vitenarkiv Vis sammendrag

  Chromium (II) fluoroperovskites A CrF 3 ( A = Na + , K + ) are strongly correlated Jahn-Teller active materials at low temperatures. In this paper, we examine the role that the A -site ion plays in this family of fluoroperovskites using both experimental methods (x-ray diffraction, optical absorption spectroscopy, and magnetic fields) and density functional theory simulations. Temperature-dependent optical absorption experiments show that the spin-allowed transitions E 2 and E 3 only merge completely for A = Na at 2 K. Field-dependent optical absorption measurements at 2 K show that the oscillating strength of the spin-allowed transitions in NaCrF 3 increases with increasing applied field. Direct magneto-optical correlations suppress the spin-flip transitions for KCrF 3 below its Néel temperature. In NaCrF 3 the spin-flip transitions vanish abruptly below 9 K revealing magneto-optical correlations possibly linked to crystal structure changes. This suggests that as the long range ordering is reduced, local Jahn-Teller effects in the individual CrF 4 − 6 octahedra take control of the observed behavior. Our results show clear deviation from the pattern found for the isoelectronic A x MnF 3 + x system. The size of the A -site cation is shown to be central in dictating the physical properties and phase transitions in A CrF 3 , opening up the possibility of varying the composition to create novel states of matter with tunable properties.

• Polfus, Jonathan; Peters, Thijs; Bredesen, Rune & Løvvik, Ole Martin (2021). Vacancy diffusion in palladium hydrides. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 23(24), s. 13680–13686. doi: 10.1039/d1cp01960k. Fulltekst i vitenarkiv
• Graff, Joachim Seland; Schuler, Raphael; Song, Xin; Castillo-Hernandez, Gustavo; Skomedal, Gunstein & Enebakk, Erik [Vis alle 11 forfattere av denne artikkelen] (2021). Fabrication of a Silicide Thermoelectric Module Employing Fractional Factorial Design Principles. Journal of Electronic Materials. ISSN 0361-5235. 50, s. 4041–4049. doi: 10.1007/s11664-021-08902-y. Fulltekst i vitenarkiv Vis sammendrag

  Thermoelectric modules can be used in waste heat harvesting, sensing, and cooling applications. Here, we report on the fabrication and performance of a four-leg module based on abundant silicide materials. While previously optimized Mg2Si0.3Sn0.675Bi0.025 is used as the n-type leg, we employ a fractional factorial design based on the Taguchi methods mapping out a four-dimensional parameter space among Mnx-εMoεSi1.75−δGeδ higher manganese silicide compositions for the p-type material. The module is assembled using a scalable fabrication process, using a Cu metallization layer and a Pb-based soldering paste. The maximum power output density of 53 μW cm–2 is achieved at a hot-side temperature of 250 °C and a temperature difference of 100 °C. This low thermoelectric output is related to the high contact resistance between the thermoelectric materials and the metallic contacts, underlining the importance of improved metallization schemes for thermoelectric module assembly.

• Løvvik, Ole Martin; Flage-Larsen, Espen & Skomedal, Gunstein (2020). Screening of thermoelectric silicides with atomistic transport calculations. Journal of Applied Physics. ISSN 0021-8979. 128. doi: 10.1063/5.0008198. Fulltekst i vitenarkiv Vis sammendrag

  More than 1000 crystalline silicide materials have been screened for thermoelectric properties using first-principles atomistic calculations coupled with the semi-classical Boltzmann transport equation. Compounds that contain radioactive, toxic, rare, and expensive elements as well as oxides, hydrides, carbides, nitrides, and halides have been neglected in the study. The already well-known silicides with good thermoelectric properties, such as SiGe, Mg2Si, and MnSix, are successfully predicted to be promising compounds along with a number of other binary and ternary silicide compositions. Some of these materials have only been scarcely studied in the literature, with no thermoelectric properties being reported in experimental papers. These novel materials can be very interesting for thermoelectric applications provided that they can be heavily doped to give a sufficiently high charge carrier concentration and that they can be alloyed with isoelectronic elements to achieve adequately low phonon thermal conductivity. The study concludes with a list of the most promising silicide compounds that are recommended for further experimental and theoretical investigations.

• Polfus, Jonathan Marc; Løvvik, Ole Martin; Bredesen, Rune & Peters, Thijs (2020). Hydrogen induced vacancy clustering and void formation mechanisms at grain boundaries in palladium. Acta Materialia. ISSN 1359-6454. 195, s. 708–719. doi: 10.1016/j.actamat.2020.06.007. Fulltekst i vitenarkiv Vis sammendrag

  Hydrogen has a significant impact on the formation of vacancies, clusters and voids in palladium and other metals. The formation of vacancy-hydrogen complexes in bulk Pd and at Σ3 and Σ5 grain boundaries was investigated using first-principles calculations and thermodynamic models. Equilibrium vacancy and cluster concentrations were evaluated as a function of temperature and hydrogen partial pressure based on the Gibbs energy of formation including vibrational and configurational entropies. Vacancies were found to be significantly stabilized by association with interstitial hydrogen, leading to enhanced concentrations by several orders of magnitude. Vacancy clusters were further stabilized at grain boundaries, with equilibrium concentrations reaching site saturation for clusters comprising up to three vacancies. Nanovoids were investigated based on Wulff constructions from calculated surface energies of the (0 0 1) and (1 1 1) terminations as a function of temperature and coverage of hydrogen adsorbates. The most stable termination changed from (1 1 1) in vacuum to (0 0 1) in H2, and the surface energies were lowered due to hydrogen adsorbates. Consequently, voids were also stabilized in the presence of hydrogen. Coalescing of vacancies into nanovoids was found to be thermodynamically unfavorable due to the loss of configurational entropy. It was therefore concluded that enhanced concentrations of vacancies and clusters does not directly cause the formation of voids. The formation of voids in Pd-based membranes was discussed in terms of microstructural characteristics, and strain due to chemical expansion and plastic deformation.

• Bernal, Fabian Leonardo Martinez; Sottmann, Jonas; Wragg, David; Fjellvåg, Helmer; Fjellvåg, Øystein & Drathen, Christina [Vis alle 8 forfattere av denne artikkelen] (2020). Structural and magnetic characterization of the elusive Jahn-Teller active NaCrF3. PHYSICAL REVIEW MATERIALS. ISSN 2475-9953. 4(5). doi: 10.1103/PhysRevMaterials.4.054412. Fulltekst i vitenarkiv
• Remonato, Filippo; Løvvik, Ole Martin & Flage-Larsen, Espen (2019). Effectiveness of Neural Networks for Research on Novel Thermoelectric Materials. A Proof of Concept. Nordic Artificial Intelligence Research and Development: Third Symposium of the Norwegian AI Society, NAIS 2019. Springer. ISSN 978-3-030-35664-4. s. 69–77. doi: 10.1007/978-3-030-35664-4_7. Fulltekst i vitenarkiv Vis sammendrag

  This paper describes the application of neural network approaches to the discovery of new materials exhibiting thermoelectric properties. Thermoelectricity is the ability of a material to convert energy from heat to electricity. At present, only few materials are known to have this property to a degree which is interesting for use in industrial applications like, for example, large-scale energy harvesting [3, 8]. We employ a standard neural network architecture with supervised learning on a training dataset representing materials and later predict the properties on a disjoint test set. At this proof of concept stage, both sets are synthetically generated with plausible values of the features. A substantial increase in performance is seen when utilising available physical knowledge in the machine learning model. The results show that this approach is feasible and ready for future tests with experimental laboratory data.

• Zhang, H.; Hippalgaonkar, K.; Buonassisi, T.; Løvvik, Ole Martin; Sagvolden, Espen & Ding, D. (2019). Machine Learning for Novel Thermal-Materials Discovery: Early Successes, Opportunities, and Challenges. Engineered Science. ISSN 2576-988X. 2, s. 1–8. doi: 10.30919/esee8c209.
• Berland, Kristian; Shulumba, Nina; Hellman, Olle; Persson, Clas & Løvvik, Ole Martin (2019). Thermoelectric transport trends in group 4 half-Heusler alloys. Journal of Applied Physics. ISSN 0021-8979. 126(14), s. 1–15. doi: 10.1063/1.5117288. Fulltekst i vitenarkiv Vis sammendrag

  The thermoelectric properties of 54 different group 4 half-Heusler (HH) alloys have been studied from first principles. Electronic transport was studied with density functional theory using hybrid functionals facilitated by the k⋅p method, while the temperature-dependent effective potential method was used for the phonon contributions to the figure of merit ZT. The phonon thermal conductivity was calculated including anharmonic phonon-phonon, isotope, alloy, and grain-boundary scattering. HH alloys have an XYZ composition, and those studied here are in the group 4-9-15 (Ti,Zr,Hf)(Co,Rh,Ir)(As,Sb,Bi) and group 4-10-14 (Ti,Zr,Hf)(Ni,Pd,Pt)(Ge,Sn,Pb). The electronic part of the thermal conductivity was found to significantly impact ZT and thus the optimal doping level. Furthermore, the choice of functional was found to significantly affect thermoelectric properties, particularly for structures exhibiting band alignment features. The intrinsic thermal conductivity was significantly reduced when alloy and grain-boundary scattering were accounted for, which also reduced the spread in thermal conductivity. It was found that sublattice disorder on the Z-site, i.e., the site occupied by group 14 or 15 elements, was more effective than X-site substitution, occupied by group 4 elements. The calculations confirmed that ZrNiSn, ZrCoSb, and ZrCoBi based alloys display promising thermoelectric properties. A few other n-type and p-type compounds were also predicted to be potentially excellent thermoelectric materials, given that sufficiently high charge carrier concentrations can be achieved. This study provides insight into the thermoelectric potential of HH alloys and casts light on strategies to optimize the thermoelectric performance of multicomponent alloys.

• Larsson, Andreas; Tollefsen, Torleif Andre; Løvvik, Ole Martin & Aasmundtveit, Knut (2019). A Review of Eutectic Au-Ge Solder Joints. Metallurgical and Materials Transactions A. ISSN 1073-5623. 50(10), s. 4632–4641. doi: 10.1007/s11661-019-05356-0. Fulltekst i vitenarkiv Vis sammendrag

  Gold-germanium (Au-Ge) joints have been part of the electronics industry since the birth of the solid state transistor. Today they find their role as a reliable joining technology, especially for high-temperature applications. This article is a literature study reviewing Au-Ge joints: Their uses, properties, material compatibility, application techniques, and performance characteristics. The review concludes that it is possible to create high-quality and very strong Au-Ge joints with a shear strength up to 150 MPa. They are stable and reliable, showing limited degradation after thousands of hours at high temperature and thousands of thermal cycles. Joints may be used in low-stress applications up to 300 °C.

• Bondevik, Tarjei; Ness, Heine Håland; Bazioti, Kalliopi; Norby, Truls Eivind; Løvvik, Ole Martin & Koch, Christoph T. [Vis alle 7 forfattere av denne artikkelen] (2019). Investigation of the electrostatic potential of a grain boundary in Y-substituted BaZrO3 using inline electron holography. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 21(32), s. 17662–17672. doi: 10.1039/c9cp02676b. Fulltekst i vitenarkiv Vis sammendrag

  We apply inline electron holography to investigate the electrostatic potential across an individual BaZr0.9Y0.1O3 grain boundary. With holography, we measure a grain boundary potential of −1.3 V. Electron energy loss spectroscopy analyses indicate that barium vacancies at the grain boundary are the main contributors to the potential well in this sample. Furthermore, geometric phase analysis and density functional theory calculations suggest that reduced atomic density at the grain boundary also contributes to the experimentally measured potential well.

• Pike, Nicholas & Løvvik, Ole Martin (2019). Calculation of the anisotropic coefficients of thermal expansion: A first-principles approach. Computational Materials Science. ISSN 0927-0256. 167, s. 257–263. doi: 10.1016/j.commatsci.2019.05.045. Fulltekst i vitenarkiv Vis sammendrag

  Predictions of the anisotropic coefficients of thermal expansion are needed to not only compare to experimental measurement, but also as input for macroscopic modeling of devices which operate over a large temperature range. While most current methods are limited to isotropic systems within the quasiharmonic approximation, our method uses first-principles calculations and includes anharmonic effects to determine the temperature-dependent properties of materials. These include the lattice parameters, anisotropic coefficients of thermal expansion, isotherm bulk modulus, and specific heat at constant pressure. Our method has been tested on two compounds (Cu and AlN) and predicts thermal properties which compare favorably to experimental measurement over a wide temperature range.

• Bondevik, Tarjei; Kuwabara, Akihide & Løvvik, Ole Martin (2019). Application of machine learning-based selective sampling to determine BaZrO3 grain boundary structures . Computational Materials Science. ISSN 0927-0256. 164, s. 57–65. doi: 10.1016/j.commatsci.2019.03.054. Fulltekst i vitenarkiv
• Pike, Nicholas; Matt, Amina & Løvvik, Ole Martin (2019). Determining the Optimal Phase-Change Material via High-Throughput Calculations. MRS Advances. ISSN 2059-8521. doi: 10.1557/adv.2019.235.

Se alle arbeider i Cristin

• Bjorå, Charlotte Sletten; Jemterud, Torkild; Løvvik, Ole Martin & Sletsjøe, Arne Bernhard (2024). Abels tårn. [Radio]. NRK P2.
• Vestre, Katharina; Mossige, Joachim; Løvvik, Ole Martin & Jemterud, Torkild (2024). Abels tårn 12.1.2024. [Radio]. Abels tårn NRK P2.
• Løvvik, Ole Martin (2024). Hvor tynt kan gull bli og hvorfor er jorda full av tunge grunnstoffer? [Radio]. Intervju i Abels tårn, NRK P2.
• Delsett, Lene Liebe; Løvvik, Ole Martin; Strumke, Inga & Jemterud, Torkild (2023). Abels tårn - Den viktigste forskninga i 2022. [Radio]. NRK P2.
• Marthinsen, Astrid; Marchand, Daniel; Ringdalen, Inga Gudem; Zhang, Kai; Løvvik, Ole Martin & Du, Qiang [Vis alle 11 forfattere av denne artikkelen] (2023). Transforming ideas into reality: exploring the power of numerical modelling & simulation tools for material and process development.
• Rahman, Jamil Ur; Gunnæs, Anette Eleonora; Finstad, Terje Gunnar; Løvvik, Ole Martin & Almeida Carvalho, Patricia (2023). Structure of a high entropy Heusler antimonide.
• Rønning, Sissel Beate; Uggerud, Einar & Løvvik, Ole Martin (2023). Abels tårn - Hvordan bør oppvaskkosten oppbevares? [Radio]. NRK Radio. Vis sammendrag

  - Er selv brød ultraprosessert, og gjør det noe? - Lading av powerbank på tur - Bør man la oppvaskkosten ligge i vasken eller henge den opp? - Hva er best: oppvaskkost eller svamp? - Hva ville en kjemiker kunne lage hvis hen ble kasta 2000 år tilbake i tid? - Hvordan ville det vært å bevege seg rundt inni jorda, dersom den var hul? - Er kværna rødt kjøtt mer usunt enn en hel biff? - Kan man lage en stjerne av vann? I panelet: Sissel Beate Rønning - Genteknolog og matforsker Einar Uggerud - Kjemiker Ole Martin Løvvik - Fysiker

• Løvvik, Ole Martin (2023). Storsatsing på utvikling av materialer med automatisering og kunstig intelligens. [Radio]. Intervju i Abels tårn.
• Løvvik, Ole Martin (2023). Om varmepumper, magnetisme og tyngdekraft. [Radio]. Intervju i Abels tårn.
• Løvvik, Ole Martin (2023). Norwegian efforts towards a materials acceleration platform: combining high-throughput experiments, modelling, and machine learning/artificial intelligence.
• Finstad, Terje Gunnar; Mayandi, Jeyanthinath; Soltani, Nayereh; Pokle, Anuj; Løvvik, Ole Martin & Almeida Carvalho, Patricia (2023). TiFe2Si Thin Films.
• Tranås, Rasmus André; Løvvik, Ole Martin & Berland, Kristian (2023). Screening of low lattice thermal conductivity materials using active learning.
• Løvvik, Ole Martin (2023). Hvor dramatisk er det å la kjøleskapdøra stå åpen flere minutter? [TV]. Intervju i Praktisk Info med Jon Almaas, TV Norge.
• Rahman, Jamil Ur; Sunding, Martin Fleissner; Løvvik, Ole Martin; Gunnæs, Anette Eleonora; Finstad, Terje Gunnar & Almeida Carvalho, Patricia (2023). Deciphering the structure of a high-entropy Heusler antimonide.
• Løvvik, Ole Martin (2023). Plast som leder strøm og andre nye materialer for det grønne skiftet. [Radio]. Intervju i Ekko, NRK P2.
• Løvvik, Ole Martin (2023). Abels tårns årskavalkade – nye materialer og maskinlæring. [Radio]. Intervju i Abels tårn, NRK P2.
• Løvvik, Ole Martin; Rahman, Jamil Ur; Finstad, Terje Gunnar; Gunnæs, Anette Eleonora & Almeida Carvalho, Patricia (2022). Thermoelectric properties of multiple component (high entropy) silicides and antimonides.
• Løvvik, Ole Martin (2022). Thermoelectrics of alloys and intermetallic materials: potential benefits and challenges of using SPS.
• Løvvik, Ole Martin (2022). Hvordan få strøm fra varme – uten bevegelige deler?
• Løvvik, Ole Martin (2022). Bør du lukke døra til komfyren når den er ferdig med å steke? [TV]. Intervju i Praktisk Info med Jon Almaas, TV Norge.
• Løvvik, Ole Martin (2022). Er virkelig norsk olje verdens reneste? [Radio]. Intervju i Abels bakgård, NRK P2.
• Løvvik, Ole Martin (2022). Vind, vann og sol kan stille hele verdens energibehov innen 2050. [Radio]. Intervju i Abels bakgård, NRK P2.
• Løvvik, Ole Martin; Carvalho, Patricia A.; Stange, Marit Synnøve Sæverud; Sunding, Martin Fleissner; Rajput, Kalpna & Larsen, Aleksander Amble [Vis alle 9 forfattere av denne artikkelen] (2022). Elastocaloric cooling with TiNiCuZr alloys?
• Tranås, Rasmus André; Løvvik, Ole Martin & Berland, Kristian (2022). Material Informatics: Machine Learning with Active Sampling for Small Training Sets.
• Tranås, Rasmus André; Løvvik, Ole Martin & Berland, Kristian (2022). Finding Low Lattice Thermal Conductivity Compounds in Materials Space: Machine Learning with Active Sampling .
• Tranås, Rasmus André; Løvvik, Ole Martin & Berland, Kristian (2022). Alloying leads to drastic reduction of lattice thermal conductivity of half-Heusler compounds.
• Tranås, Rasmus André; Berland, Kristian; Tomic, Oliver & Løvvik, Ole Martin (2022). Discovering Energy Materials: Low Thermal Conductivity Thermoelectric Compounds and Barocaloric Compounds.
• Løvvik, Ole Martin; Schrade, Matthias; Grimenes, Øven Andreas; Tranås, Rasmus André & Berland, Kristian (2022). Predictive screening for thermoelectric properties using atomic-scale simulations and machine learning tools.
• Løvvik, Ole Martin (2022). Abels tårn: Artig underholdning eller nyttig kunnskap?
• Løvvik, Ole Martin (2022). Jordvarme, kjernekraft og batterier. [Radio]. Intervju i Abels tårn, NRK P2.
• Løvvik, Ole Martin (2021). Pepperkakehus, stearinlys og sprø ribbe. [Radio]. Intervju i Abels tårn, NRK P2.
• Løvvik, Ole Martin (2021). Vi skal utvikle materialer for fornybar energi ti ganger raskere enn i dag. Apollon : Forskningsmagasin for Universitetet i Oslo. ISSN 0803-6926. 4/2021, s. 21–22.
• Løvvik, Ole Martin (2021). Magneter, solceller og isbiter. [Radio]. Abels tårn, NRK P2.
• Løvvik, Ole Martin (2021). Screening of materials for thermoelectric conversion of heat into electricity.
• Løvvik, Ole Martin (2021). Casting Materials Acceleration Platform and the accelerated search for thermoelectric materials.
• S. Azar, Amin; Schrade, Matthias; Graff, Joachim Seland; Flage-Larsen, Espen; Løvvik, Ole Martin & Belle, Branson [Vis alle 8 forfattere av denne artikkelen] (2021). Structural and magnetic performance of soft magnets based on FeCoNiMnAl additively manufactured high entropy alloys.
• Bazioti, Kalliopi; Poulia, Anthoula; Løvvik, Ole Martin; S. Azar, Amin; Mikheenko, Pavlo & Diplas, Spyridon [Vis alle 7 forfattere av denne artikkelen] (2021). Structural evolution of FeCoNi(AlMn)x high-entropy alloy and impact on magnetic properties: nano-scale STEM-EELS investigations.
• Mayandi, Jeyanthinath; Finstad, Terje; Stange, Marit Synnøve Sæverud; Vasque, Giovanni; Sunding, Martin Fleissner & Løvvik, Ole Martin [Vis alle 8 forfattere av denne artikkelen] (2021). Engineering Electrical Properties of Reactively Sputtered High Entropy Alloy CrFeNiCoCu Films. Vis sammendrag

  Oxide containing films were deposited by reactive sputtering using a high entropy alloy (HEA) target made of equal concentrations of the five 3d-transion metals: Cr, Fe, Co, Ni, and Cu. We report on controlled alterations to the electrical properties made by post-deposition heat treatments in oxidizing and reducing atmospheres respectively. The temperature coefficient of resistivity of the films could be varied between -1.2×10-3 K-1 through 0 and to +0.7×10-3 K-1, while the measured effective resistivity could be varied between 1.3×10-4 Ωcm and 1.2×10-3 Ωcm by post deposition processing. To study the transport mechanisms, we performed temperature dependent Hall effect measurements down to 10 K. We correlated the electrical behavior with structural measurements by a combination of X-ray diffraction (XRD), scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) for elemental mapping at various length scales and secondary ions mass spectroscopy (SIMS). The key to engineering the resistivity is controlling the topology of the film. The topology of the as- deposited thin films can be controlled by the oxygen flow during reactive sputtering as the most important parameter. For zero oxygen flow we have obtained a homogenous HEA film having a FCC structure with the CrFeNiCoCu target. For high oxygen flow we have observed a high entropy oxide with a rock salt crystal structure. Here we report on the case of intermediate flow of oxygen. The as-deposited structure is then complex. There are nano sized regions with oxides and regions with FCC HEA alloys with different compositions of all the 3d-metals but also supersaturated with oxygen. The topology of these regions, and also their concentration, can be altered by post-deposition heat treatment. The transport in the HEA regions are dominated by alloy scattering. The potential in the FCC HEA has disorder due to the random mixing of the elements, which also gives distortion of the individual atom sites. This gives resistivities above the Mott- Ioffe-Regel limit while still having a positive TCR. These disorder effects will be further enhanced by the uptake of oxygen atoms. For these cases one gets weak localization, yielding a negative TCR. The oxides may be insulating but may also conduct by variable range hopping of the Efros–Shklovskii-type or the Mott- type yielding characteristic negative TCR. The post-deposition yields oxide segregation, of for example of spinel type containing Cr. This reduce the entropy and stability of the metal alloy, creating FCC and BCC metal alloys of different compositions. In the case of reducing the heat treatment in a reducing atmosphere, the oxides are reduced. The experimental resistivities are in excellent agreement with the model for the conduction.

• Bazioti, Kalliopi; Poulia, Anthoula; Løvvik, Ole Martin; S. Azar, Amin; Mikheenko, Pavlo & Diplas, Spyridon [Vis alle 7 forfattere av denne artikkelen] (2021). Advanced Scanning Transmission Electron Microscopy investigations of FeCoNi(AlMn)x high-entropy alloy: nanoscale structure and impact on magnetic properties.
• Bazioti, Kalliopi; Poulia, Anthoula; Løvvik, Ole Martin; Almeida Carvalho, Patricia; S. Azar, Amin & Mikheenko, Pavlo [Vis alle 8 forfattere av denne artikkelen] (2021). STEM-EELS investigations and Lorentz microscopy unravelling the structural evolution of FeCoNi(AlMn)x high-entropy alloy and its impact on magnetic properties.
• Tranås, Rasmus André; Løvvik, Ole Martin; Tomic, Oliver & Berland, Kristian (2021). Active sample selection for finding low lattice thermal conductivity materials using machine learning .
• Løvvik, Ole Martin (2021). Effektivitet og pris av batterier i batteribanker og nettbrett. [Radio]. Intervju i Abels tårn, NRK P2.
• Tranås, Rasmus André; Berland, Kristian; Løvvik, Ole Martin & Tomic, Oliver (2021). Fingerprints of low lattice thermal conductivity compounds: half-Heusler case study and beyond.
• Løvvik, Ole Martin (2021). Volum av Li-batterier og horisontale raketter. [Radio]. Intervju i Abels tårn, NRK P2.
• Løvvik, Ole Martin (2020). Uranglassur og enorme vindmøller. [Radio]. Intervju i Abels tårn, NRK P2.
• Jemterud, Torkild; Danielsen, Anne; Brodal, Per; Løvvik, Ole Martin; Goodwin, Morten & Knudsen, Pål Moddi (2020). Abels tårn: En følsom AI tester visesang. Vis sammendrag

  Kan en AI lage bedre tekster enn en visesanger? Og bedre drinker enn en bartender? Vi tester begge deler. Prøvekanin er Pål Moddi Knudsen. En AI har tygd seg gjennom de gamle tekstene hans, og spytta ut en splitter ny. Dessuten - Hvorfor hører man bare bassen fra festen ved siden av? - Konsentrer man seg bedre med musikk? - Løper man raskere med musikk? - Hvorfor har vi så ulik musikksmak? - Hvorfor er Moddis gitar alltid sur? - Hvor varmt blir det i en peisovn? I panelet Visesanger Pål Moddi Knudsen Datalog Morten Goodwin Musikkviter Anne Danielsen Fysiker Ole Martin Løvvik Hjerneforsker Per Brodal

• Løvvik, Ole Martin (2020). Elektronikk i varme omgivelser og termoelektriske generatorer. [Radio]. Intervju i Abels tårn, NRK P2.
• Jeyanthinath, Mayandi; Stange, Marit Synnøve Sæverud; Dahl, Øystein; Sunding, Martin Fleissner; Sagvolden, Espen & Flage-Larsen, Espen [Vis alle 13 forfattere av denne artikkelen] (2020). Functional Properties of CrFeCoNiCu and GeFeCoNiCu oxides. Vis sammendrag

  The present work explores the concept of high-entropy alloys to design FeCoNi-based oxides suitable for functional applications. Fundamental changes in electronic behavior produced by metal substitution and variable oxygen content were screened to investigate the potential of these materials for specific applications, such as transparent conductors and thermoelectric materials. Elements with atomic radius similar to the average value expected for FeCoNi have been selected for substitutional replacement: (i) Cr and Cu as relatively abundant commodities with intensive industrial application and (ii) Ge due its semiconductor nature. CrFeCoNiCu and GeFeCoNiCu thin films with variable oxygen concentration were deposited by reactive DC magnetron sputtering onto optically transparent substrates and characterized by structural, spectroscopic and electrical methods. Transmission electron microscopy showed that for low oxygen content the materials adopted an fcc-type structure while the NaCl-structure was found for higher oxygen concentrations. X-ray-photoelectron spectroscopy was used to characterize the oxidation state of the metals. The resistivity measured at room temperature ranged from 10-4 to values above 104 Ω.cm. Hall measurements and Seebeck measurements show that both electrons and holes contribute to conduction and that at room temperature the Hall coefficient and Seebeck coefficient have different sign. This behaviour is discussed in terms of the structural analysis and suggested electronic model of the films.

• Løvvik, Ole Martin; Graff, Joachim Seland; Schrade, Matthias; Sunding, Martin Fleissner; Wright, Daniel Nilsen & Song, Xin [Vis alle 10 forfattere av denne artikkelen] (2020). Silicide module produced in the TESil project.
• Løvvik, Ole Martin (2020). Palladium membranes for hydrogen separation - interesting for nanoparticles?
• Løvvik, Ole Martin (2020). Energy Conversion Using Phase Transformations.
• Løvvik, Ole Martin (2020). Mission Innovation – inspiration for new infrastructure in Norway.
• Mayandi, Jeyanthinath; Stange, Marit Synnøve Sæverud; Sagvolden, Espen; Sunding, Martin Fleissner; Dahl, Øystein & Schrade, Matthias [Vis alle 12 forfattere av denne artikkelen] (2019). Structural and Electrical Properties of Sputtered HEA Thin Films of CrFeCoNiCu and their Oxidation Studies. Vis sammendrag

  High-entropy alloys (HEAs) represent a class of materials that is intensively investigated for a range of possible applications. They generally show a high degree of phase stability by the high entropy while the structure is a random atom position disorder unlike other alloys which can influence physical properties differently than regular alloys. In general, there are few studies on oxidation of HEA and studies on adding oxygen during the fabrication of HEA. In this study we have sputtered thin films of CrFeCoNiCu onto insulating and optically transparent substrates in order to measure structural, electrical and optical functional properties. We have varied the oxygen pressure in the sputtering environment as well as oxidizing the samples at elevated temperatures after deposition. Optical and electrical characterization was performed on films sputter deposited on fused quartz wafers. The films were characterized by TEM, XRD and XPS. The films with no intentional oxygen had an FCC structure with a texture showing strong (111) preferred orientation as seen by XRD. TEM analysis showed columnar morphology with twins parallel to (111) planes. Samples sputtered under high oxygen content showed a simple NaCl structure(FeO). The samples were annealed in air and O2 ambient in the temperature range of 300 to 500 °C. This caused an oxide layer growing on top of the FCC structure. XPS was utilized to find the atomic compositions and chemical stated of the elements. Hall measurements and Seebeck measurements were performed on the as prepared and oxidized films from 10 K to 600K. For the FCC structure the resistivity was a factor 104 higher than the elemental metals while can be satisfactory described by electron phonon scattering by the Bloch-Grüneisen description and the low temperature negative temperature effect by the Kondo effect. The sign of the Hall coefficient was positive while the Seebeck coefficient was negative, indicating the Fermi surface containing pockets of electrons and holes and an energy dependent scattering time. A detailed comparison of the as prepared and the oxidized thin films will be discussed in terms of the structural chemical and electrical properties of the grown films. In addition the electric properties will be discussed in terms of a model considering electronic structure and scattering.

• Mayandi, Jeyanthinath; Stange, Marit Synnøve Sæverud; Sunding, Martin Fleissner; Schrade, Matthias; Deuermeier, J. & Fortunato, E. [Vis alle 10 forfattere av denne artikkelen] (2019). Physical properties of sputtered CrFeCoNiCu thin films on quartz substrate. Vis sammendrag

  Equiatomic high entropy alloys (HEA) have attracted considerable interest due to their exceptional properties, which might be closely related to their extreme disorder induced by chemical complexity. We have sputtered thin films of CrFeCoNiCu onto insulating and optically transparent substrates in order to measure electrical and optical functional properties. After several optimizations desired sputtering conditions were obtained for the deposition of CrFeCoNiCu onto fused quartz wafers. All the samples were characterized by structural, chemical and electrical methods. The as prepared films had fcc-type structure. Hall measurements were performed from 10 K to 600K. The resistivity was a factor 104 higher than the elemental metals and the temperature dependence was different. The sign of the Hall coefficient indicates that the film was dominated by holes, while the Seebeck coefficient was negative and dominated by electrons. The electric properties will be discussed in terms of a model considering electronic structure and scattering.

• Løvvik, Ole Martin; Flage-Larsen, Espen & Skomedal, Gunstein (2019). Atomistic simulations and machine learning methods for development of thermoelectric materials.
• Løvvik, Ole Martin (2019). Batteriteknologi. [Radio]. Intervju i Ekko, NRK P2.
• Løvvik, Ole Martin (2019). Hvor miljøvennlig er en elbil? [Radio]. Intervju i Abels Tårn, NRK P2.
• Løvvik, Ole Martin (2019). Nye løsninger for å lage strøm av spillvarme kan gi muligheter for norsk industri. Kommentarer i artikkelen. Teknisk Ukeblad. ISSN 0040-2354.
• Løvvik, Ole Martin; Berland, Kristian; Remonato, Filippo; Sagvolden, Espen; Flage-Larsen, Espen & Schrade, Matthias [Vis alle 13 forfattere av denne artikkelen] (2019). Screening thermoelectric materials with ab initio atomistic modelling and machine learning techniques.
• Løberg, Monika; Karlsen, Ole Bjørn; Løvvik, Ole Martin; Almeida Carvalho, Patricia & Gunnæs, Anette Eleonora (2019). Characterization of phase transformations within the Cu-Pd-Sn system - a possible shape memory alloy for energy conversion.
• Løberg, Monika; Pike, Nicholas; Almeida Carvalho, Patricia; Karlsen, Ole Bjørn; Løvvik, Ole Martin & Gunnæs, Anette Eleonora (2019). Martensitic-like phase transformations within the Cu-Pd-Sn system .
• Løberg, Monika; Løvvik, Ole Martin; Almeida Carvalho, Patricia; Karlsen, Ole Bjørn & Gunnæs, Anette Eleonora (2019). Phase Transformations within the Cu-Pd-Sn system.
• Løberg, Monika; Pike, Nicholas; Karlsen, Ole Bjørn; Almeida Carvalho, Patricia; Løvvik, Ole Martin & Gunnæs, Anette Eleonora (2019). Characterization of phase transforming, Heusler based (Cu-Pd-Sn), alloys for energy harvesting. .
• Sunding, Martin Fleissner; Løberg, Monika; S. Azar, Amin; Stange, Marit Synnøve Sæverud; Almeida Carvalho, Patricia & Karlsen, Ole Bjørn [Vis alle 10 forfattere av denne artikkelen] (2019). The Need for a Multi-Technique Approach in the Search for New Phase-Transforming Materials. Vis sammendrag

  Introduction/Purpose Reversible diffusionless first-order phase transformations are a fundamental part of phase change materials and shape memory alloys [1]. Some of these materials even possess useful physical characteristics that show abrupt changes e.g. in their electrical[2] and magnetic [3] polarizations. These phase transformations can be studied using multiple techniques, enabling access to different types of information including length scales and time periods, but how should this characterisation be approached? Methods TEM studies give highly relevant data in this field of research, from detailed crystallographic structures, to relative orientations between grains and phases and to the phase transformation temperature. However, TEM analyses are time consuming and requires small sample sizes and ad hoc preparation. High-throughput measurement techniques are thus required in the search for improved compositions and new materials in order to rapidly assess the properties of many samples or samples with graded composition [4]. Optical methods (for example unpolarised and polarised microscopy and thermal imaging) and electric conductivity measurements can for example be used to map phase transformation temperatures much faster and on much larger areas than traditional TEM techniques. XRD and SEM-EDS-EBSD can then be applied to obtain initial crystallographic and microstructure information on an intermediate size scale, before TEM is applied for the in-depth study of the most relevant compositions. Results We applied this multi-pronged approach in the search for Heusler and half-Heusler alloys with a low temperature martensitic phase transformation and with low thermal hysteresis, with potential applications in waste heat energy harvesting. Conclusions Drawing advantage of the strengths of multiple analysis techniques – with respect to the obtainable information, the sample size and/or the time frame of the analyses – renders the search for new phase change materials more effective. It enables faster identification of potential target compositions and of sample areas optimal for in depth studies. Selected references [1] David Dye, Nature Materials14 (8), 760 (2015). [2] M. M. Vopson, Critical Reviews in Solid State and Materials Sciences40 (4), 223 (2015). [3] L. Huang, D. Y. Cong, L. Ma, Z. H. Nie, Z. L. Wang, H. L. Suo, Y. Ren, and Y. D. Wang, Applied Physics Letters108 (3) (2016). [4] M. L. Green, C. L. Choi, J. R. Hattrick-Simpers, A. M. Joshi, I. Takeuchi, S. C. Barron, E. Campo, T. Chiang, S. Empedocles, J. M. Gregoire, A. G. Kusne, J. Martin, A. Mehta, K. Persson, Z. Trautt, J. Van Duren, and A. Zakutayev, Applied Physics Reviews 4 (1), 011105 (2017).

• Mayandi, Jeyanthinath; Stange, Marit Synnøve Sæverud; Dahl, Øystein; Sunding, Martin Fleissner; Sagvolden, Espen & Schrade, Matthias [Vis alle 12 forfattere av denne artikkelen] (2019). Exploring functional properties of high entropy oxides. Vis sammendrag

  The present work explores the concept of high-entropy alloys to design FeCoNi-based oxides suitable for functional applications. Fundamental changes in electronic behaviour produced by metal substitution and variable oxygen content were screened to investigate the potential of these materials for specific applications, such as transparent conductors and thermoelectric materials. Elements with atomic radius similar to the average value expected for FeCoNi have been selected for substitutional replacement: (i) Cr and Cu as relatively abundant commodities with intensive industrial application and (ii) Ge due its semiconductor nature. We have sputtered CrFeCoNiCu and of GeFeCoNiCu thin films onto insulating and optically transparent substrates in order to measure electrical and optical properties. The deposition was done by reactive DC magnetron sputtering from targets with equimolar proportions of the metallic elements using atmospheres ranging from 0 to 20 at.% O2 /Ar. The films where characterized by structural, spectroscopic and electrical methods. Transmission electron microscopy showed that for oxygen content up to 8 at.% the materials adopted an fcc-type structure while the NaCl-structure was found for higher oxygen concentrations. X-ray-photoelectron spectroscopy was used to characterize the oxidation state of the metals. Standard absorption analysis by UV-VIS spectrometry revealed that the films had bandgaps ranging from 0.8 to 2.8 eV. The resistivity measured at RT ranged from 10-4 to values above 104 Ω.cm. Hall measurements and Seebeck measurements indicated that both electrons and holes contribute to conduction and at RT the Hall coefficient and Seebeck coefficients have different sign. This behaviour is discussed in terms of the structural analysis and suggested electronic model of the films. In conclusion, the optical band gap and resistivity of the materials produced span over large ranges demonstrating potential for a variety of functional applications.

• Løvvik, Ole Martin (2019). Introduction to the COMET project.
• Mayandi, Jeyanthinath; Stange, Marit Synnøve Sæverud; Sagvolden, Espen; Sunding, Martin Fleissner; Dahl, Øystein & Schrade, Matthias [Vis alle 12 forfattere av denne artikkelen] (2019). Development of sputtered HEA thin films and their functional properties .
• Løvvik, Ole Martin (2019). Hvor sikker er en hydrogenbil? [TV]. Intervju i Dagsrevyen, NRK1.
• Jemterud, Torkild; Joner, Erik; van Oort, Bob; Dyrrdal, Anita Verpe & Løvvik, Ole Martin (2019). Abels tårn om klima. [Radio]. NRK P2.
• Løvvik, Ole Martin (2019). Klimasending fra Eidsvolls plass om bærekraft og fornybar energi. [Radio]. Intervju i Abels tårn, NRK2.
• Løvvik, Ole Martin (2019). Hvor blir kiloene av, grunnstoffer i periodesystemet. [TV]. Intervju i Abels tårn, NRK2.
• Høylo-Rosenberg, Jørn-Marcus; Løvvik, Ole Martin & Persson, Clas (2022). An ab initio study of the band gaps of high-entropy silicides based on FeSi2. Universitetet i Oslo. Vis sammendrag

  In this work we have set out to examine the band gaps of potential high-entropy stabilized transition metal silicides, based on the FeSi2 semiconductor. Here, we have performed a first principles study utilizing density functional theory in combination with the special quasi-random structures method. The band gaps has been evaluated primarily with the PBE GGA functional, but also the SCAN meta-GGA functional and hybrid functional HSE06 has been applied in this project. Potential alloys has been examined by generating a set of distinct supercells of the FeSi2 structure, where the iron sites are populated quasi-randomly by a combination of 3d transition metals. The alloys we have studied in this project are comprised of combinations of Cr, Fe, Mn, Ni, Co and Ti, most emphasis has been put on the Cr-Fe-Mn-Ni-Si system. In the (CrFeMnNi)Si2 composition, we can report several semiconducting supercells with band gaps ranging between 0 - 0.05 eV using PBE GGA. The band gaps displayed significant spin polarization, in the spin up direction most supercells pointed to a gap around 0.3 eV. Contrary, the band gaps in spin down varied between 0 - 0.05 eV. Accordingly, we found a finite magnetic moment in this alloy equal to 0.083 mu_B, this was attributed mainly to chromium and manganese atoms in the lattice. Successive simulations of alloys based on the Cr-Fe-Mn-Ni-Si system with non-equimolar distribution of 3d elements, resulted most frequently in half-metallic structures with a spin up band gap ranging between 0.1 eV and 0.5 eV. Of the different compositions we tested, the ones either rich in manganese and/or poor in chromium showed the most promise with respect to the band gap. In particular, we report a PBE total band gap equal to 0.1 eV in the Cr3Fe5Mn5Ni3Si32 composition. Lastly, we looked at compositions where either Cr, Mn or Ni were replaced by either cobalt or titanium. This yielded predominately metallic compounds, where the lack of band gaps could be ascribed to defect states at the band edges.

• Nyberg, Fredrik; Løvvik, Ole Martin & Persson, Clas (2020). Ab initio calculation of the coefficient of thermal expansion and the secondary pyroelectric vector. Universitetet i Oslo.
• Mjærum, Dagfinn Olaf Øvrevik; Persson, Clas; Berland, Kristian & Løvvik, Ole Martin (2019). Layer Stacking and Electronic Properties of Hexagonal Covalent Organic Frameworks - A Computational Investigation with van der Waals Density Functional Theory. Universitetet i Oslo. Vis sammendrag

  We have calculated the electronic properties and layer stacking patterns for a group of twelve hexagonal covalent organic frameworks. This has been done in order to explore this group of materials on a fundamental level and aim to lay the ground work for further studies, which will focus on assessing these frameworks as useful materials for electronic and optoelectronic devices. To explore these materials, we have deployed numerical density functional theory calculations. A Van der Waals density functional is used to describe non-local correlation effects that give rise to stabilizing van der Waals forces, essential in layered systems. We found that all the materials prefer to stack in specific configurations close to AA-stacking, where subsequent layers are placed directly on-top of each other. We also found that the materials exhibit dispersion in the out-of-plane direction when we go from two-dimensional single layers to three-dimensional stacks.

• Both, Kevin Gregor; Norby, Truls Eivind; Bjørheim, Tor Svendsen & Løvvik, Ole Martin (2019). Cu2O – ZnO p-n Junctions: Thermodynamics, Structure, and Properties – an Experimental and Theoretical Study. Universitetet i Oslo.
• Frøen, Emil Herman; Norby, Truls Eivind; Bjørheim, Tor Svendsen & Løvvik, Ole Martin (2019). Coexistent Oxide p-n Junctions: DFT Analysis of Interfaces Between Nickel Oxide and Zinc Oxide. Universitetet i Oslo.

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