kriberl

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Research

My scientific background is in modeling and developing tools for van der Waals interactions as well as semiconductor heterostructure physics. Currently, I am part of Prof. Clas Persson theory group at Structure Physics. This group has a general expertise on first-principle modeling of energy materials. In particular, I model thermoelectric materials as part of the national THELMA project. Starting fall 2017, emphasis will shift back to modeling van der Waals materials as part of a national project in collaboration with theoreticans from the Casimir field.

Modeling of thermoelectric materials

Method development

A key challenge in accurate modeling of thermoelectric properties in the Boltzmann transport formalism is a sufficiently dense sampling of the Brillouin zone. To tackle this , we have developed a new \(\mathrm{k}\dot\,\mathrm{p}\, \)based interpolation scheme (https://arxiv.org/abs/1607.01429). We are currently employing this scheme for a number of problems related both to thermoelectric transport and optical absorption.

Half Heuslers

Simen N. H. Eliassen studied the thermal transport of (TiZrHf)NiSn in his master thesis work. The paper is now available at https://arxiv.org/abs/1607.01429.

Half Heuslers are ternary compounds that can be viewed as an interpenetrating zinc-blende and rock-salt structure. Since three elements can be combined in many different ways and still form a closed shell, Half Heuslers makes it possible to use inexpensive, earth-abundant and environmentally friendly elements in applications such as thermoelectronics (solid state conversion of heat to electric power). Together with SINTEF and experimentalists at Structure Physics and IFE, we are exploring and optimizing these materials for thermoelectric applications.

van der Waals forces in condensed matter

Non-local correlation functionals

The van der Waals density functional (vdW-DF) has been amazingly successful in extending density functional theory calculation to materials bound together by van der Waals forces. For an overview consult our extensive review van der Waals forces in density functional theory: a review of the vdW-DF method. In the recent paper Spin Signature of Nonlocal Correlation Binding in Metal-Organic Frameworks, we also extended the method to spin-polarized systems.

Even if the modern variants of the functional, such as the vdW-DF-cx, have good performance for many systems, there are many physical effects than can be better accounted for. An example is the underlying electrodynamical screening in the method. The immense progress in the manufacturing of layered van der Waals heterostructures is also motivated developing more accurate methods, so is the desire to accurately model water, adsorption, and interactions between biomolecules. Currently, we are extending the method to encompass hybrid-exchange effects togheter with the Hyldgaard team at Chalmers.

Casimir interactions in environmental systems

Beyond the regime of systems that can be modeled with density functional theory, longer length scales not only demand a more macroscopic approach but also require that retardation effects are accounted for.

Collaboration

Collaborations with many international groups, including

Tomic Stanko, U. Salford

Jeff Neaton, UC Berkeley,

Per Hyldgaard, Chalmers

T. L. Einstein, University of Maryland

Valentino Cooper, Oak Ridge

T. Thonhauser, Wake Forest University

Background

2007 Master thesis at NTNU, theoretical high-energy physics.

2007 -2012 PhD at Chalmers University of Technology in the group of Prof. Per Hyldgaard

2012- 2014 Post Doc at Chalmers Universtiy of Technology, including a 6 months visit to Berkeley lab.

2014 Post Doc at University of Oslo

Teaching

I teach the course Quantum mechanical modeling of nanomaterials. This is a practical theory course, were student learn the skills to efficiently execute research projects were density functional theory calculations is an ingredient. The course does not only cover basic details but also emphasize good research practice in the field.

Taking advantage of the fact that there are typically only about 10 students, the course has been made quite interactive.

Master students

Simen Nut Hansen Eliassen (alumni), now PhD student at NTNU.

Tags: Thermoelectric materials, van der Waals systems, vdW-DF, Heterostructures

ResearchGate

Leon_Valido, Dario Alejandro; Elgvin, Cana; Nguyen, Phuong Dan; Prytz, Øystein; Hage, Fredrik Sydow & Berland, Kristian (2024). Unraveling many-body effects in ZnO: Combined study using momentum-resolved electron energy-loss spectroscopy and first-principles calculations. Physical review B (PRB). ISSN 2469-9950. 109(11). doi: 10.1103/PhysRevB.109.115153.
Jenkins, Trevor; Chakraborty, Debajit; Berland, Kristian & Thonhauser, Timo (2024). Reduced-gradient analysis of molecular adsorption on graphene with nonlocal density functionals. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 109(3). doi: 10.1103/PhysRevB.109.035427.
Sødahl, Elin Dypvik; Seyedraoufi, Seyedmojtaba; Gørbitz, Carl Henrik & Berland, Kristian (2023). Ferroelectric Crystals of Globular Molecules: Cambridge Structural Database Mining and Computational Assessment. Crystal Growth & Design. ISSN 1528-7483. 23(12), p. 8607–8619. doi: 10.1021/acs.cgd.3c00713. Full text in Research Archive
Li, Yang; Corkery, Robert; Carretero-Palacios, Sol; Berland, Kristian; Esteso, Victoria & Fiedler, Johannes [Show all 9 contributors for this article] (2023). Origin of anomalously stabilizing ice layers on methane gas hydrates near rock surface. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 25, p. 6636–6652. doi: 10.1039/d2cp04883c.
Sødahl, Elin Dypvik; Walker, Julian & Berland, Kristian (2023). Piezoelectric Response of Plastic Ionic Molecular Crystals: Role of Molecular Rotation. Crystal Growth & Design. ISSN 1528-7483. 23(2), p. 729–740. doi: 10.1021/acs.cgd.2c00854.
Fiedler, Johannes; Berland, Kristian; Borchert, James; Corkery, Robert; Eisfeld, Alexander & Gelbwaser-Klimovsky, David [Show all 20 contributors for this article] (2022). Perspectives on weak interactions in complex materials at different length scales. Physical Chemistry, Chemical Physics - PCCP. ISSN 1463-9076. 25, p. 2671–2705. doi: 10.1039/d2cp03349f. Full text in Research Archive Show summary
Nanocomposite materials consist of nanometer-sized quantum objects such as atoms, molecules, voids or nanoparticles embedded in a host material. These quantum objects can be exploited as a super-structure, which can be designed to create material properties targeted for specific applications. For electromagnetism, such targeted properties include field enhancements around the bandgap of a semiconductor used for solar cells, directional decay in topological insulators, high kinetic inductance in superconducting circuits, and many more. Despite very different application areas, all of these properties are united by the common aim of exploiting collective interaction effects between quantum objects. The literature on the topic spreads over very many different disciplines and scientific communities. In this review, we present a cross-disciplinary overview of different approaches for the creation, analysis and theoretical description of nanocomposites with applications related to electromagnetic properties.
Sødahl, Elin Dypvik; Walker, Julian & Berland, Kristian (2022). Piezoelectric Response of Plastic Ionic Molecular Crystals: Role of Molecular Rotation. ChemRxiv. ISSN 2573-2293. doi: 10.26434/chemrxiv-2022-fqhtl.
Fiedler, Johannes; Berland, Kristian & Buhmann, Stefan Yoshi (2022). Purcell-induced suppression of superradiance for molecular overlayers on noble atom surfaces. Journal of Chemical Physics. ISSN 0021-9606. 157(19), p. 1–15. doi: 10.1063/5.0106503. Full text in Research Archive Show summary
We study the impact of an environment on the electromagnetic responses of a molecule in the presence of a dielectric medium. By applying the dipole–dipole coupling between the molecule’s and the environment’s degrees of freedom, we can reduce the complex system into its components and predict excitation lifetimes of single and few molecules attached to a dielectric surface by knowing the entire quantum–mechanical properties of the molecules, such as transition energies and dipole moments. The derived theory allows for the description of superradiance between two molecules depending on the geometric arrangement between both concerning their separation and orientation with respect to each other. We analyze the possibility of superradiance between two molecules bound to a dielectric sphere and determine a change in the relevant length scale where the usually considered wavelength in free space is replaced with the binding distance, drastically reducing the length scales at which collective effects can take place.
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), p. 1–14. doi: 10.3390/electronicmat3010001. Full text in Research Archive
Seyedraoufi, Seyedmojtaba & Berland, Kristian (2022). Improved proton-transfer barriers with van der Waals density functionals: Role of repulsive non-local correlation. Journal of Chemical Physics. ISSN 0021-9606. 156(24). doi: 10.1063/5.0095128.
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. Full text in Research Archive Show summary
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.
Jenkins, Trevor; Berland, Kristian & Thonhauser, T. (2021). Reduced-gradient analysis of van der Waals complexes. Electronic Structure. ISSN 2516-1075. 3(3). doi: 10.1088/2516-1075/ac25d7. Full text in Research Archive
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. Full text in Research Archive Show summary
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.
Berland, Kristian; Chakraborty, Debajit & Thonhauser, T (2020). Next-Generation Nonlocal van der Waals Density Functional. Journal of Chemical Theory and Computation. ISSN 1549-9618. doi: 10.1021/acs.jctc.0c00471.
Chakraborty, D.; Berland, K. & Thonhauser, T. (2020). Next-Generation Nonlocal van der Waals Density Functional. Journal of Chemical Theory and Computation. ISSN 1549-9618. 16(9), p. 5893–5911. doi: 10.1021/acs.jctc.0c00471. Full text in Research Archive
Fiedler, Johannes; Berland, Kristian; Spallek, F.; Brevik, Iver Håkon; Persson, Clas & Buhmann, S. Y. [Show all 7 contributors for this article] (2020). Nontrivial retardation effects in dispersion forces: From anomalous distance dependence to novel traps. Physical review B (PRB). ISSN 2469-9950. 101(23). doi: 10.1103/PhysRevB.101.235424. Show summary
In the study of dispersion forces, nonretarded, retarded, and thermal asymptotes with their distinct scaling laws are regarded as cornerstone results governing interactions at different separations. Here, we show that when particles interact in a medium, the influence of retardation is qualitatively different, making it necessary to consider the nonmonotonous potential in full. We discuss different regimes for several cases and find an anomalous behavior of the retarded asymptote. It can change sign and lead to a trapping potential.
Gunnæs, Anette Eleonora; Tofan, Raluca; Berland, Kristian; Gorantla, Sandeep Madhukar; Storaas, Thomas Aarflot & Desissa, Temesgen Debelo [Show all 12 contributors for this article] (2020). Chemical stability of Ca3Co4−xO9+δ/CaMnO3−δ p–n junction for oxide-based thermoelectric generators. RSC Advances. ISSN 2046-2069. 10(9), p. 5026–5031. doi: 10.1039/c9ra07159h. Full text in Research Archive Show summary
An all-oxide thermoelectric generator for high-temperature operation depends on a low electrical resistance of the direct p–n junction. Ca3Co4−xO9+δ and CaMnO3−δ exhibit p-type and n-type electronic conductivity, respectively, and the interface between these compounds is the material system investigated here. The effect of heat treatment (at 900 °C for 10 h in air) on the phase and element distribution within this p–n junction was characterized using advanced transmission electron microscopy combined with X-ray diffraction. The heat treatment resulted in counter diffusion of Ca, Mn and Co cations across the junction, and subsequent formation of a Ca3Co1+yMn1−yO6 interlayer, in addition to precipitation of Co-oxide, and accompanying diffusion and redistribution of Ca across the junction. The Co/Mn ratio in Ca3Co1+yMn1−yO6 varies and is close to 1 (y = 0) at the Ca3Co1+yMn1−yO6–CaMnO3−δ boundary. The existence of a wide homogeneity range of 0 ≤ y ≤ 1 for Ca3Co1+yMn1−yO6 is corroborated with density functional theory (DFT) calculations showing a small negative mixing energy in the whole range.
Schrade, Matthias; Berland, Kristian; Kosinskiy, Andrey; Heremans, Joseph P. & Finstad, Terje (2020). Shallow Impurity Band in ZrNiSn. Journal of Applied Physics. ISSN 0021-8979. 127(4). doi: 10.1063/1.5112820. Full text in Research Archive Show summary
ABSTRACT ZrNiSn and related half Heusler compounds are candidate materials for efficient thermoelectric energy conversion with a reported thermoelectric figure-of-merit of n-type ZrNiSn exceeding unity. Progress on p-type materials has been more limited, which has been attributed to the presence of an impurity band, possibly related to Ni interstitials in a nominally vacant 4d position. The specific energetic position of this band, however, has not been resolved. Here, we report the results of a concerted theory-experiment investigation for a nominally undoped ZrNiSn, based on the electrical resistivity, the Hall coefficient, the Seebeck coefficient, and the Nernst coefficient, measured in a temperature range from 80 to 420 K. The results are analyzed with a semianalytical model combining a density functional theory (DFT) description for ideal ZrNiSn, with a simple analytical correction for the impurity band. The model provides a good quantitative agreement with experiment, describing all salient features in the full temperature span for the Hall, conductivity, and Seebeck measurements, while also reproducing key trends in the Nernst results. This comparison pinpoints the impurity band edge to 40 meV below the conduction band edge, which agrees well with a separate DFT study of a supercell containing Ni interstitials. Moreover, we corroborate our result with a separate study of the ZrNiSn0.9Pb0.1 sample showing similar agreement with an impurity band edge shifted to 32 meV below the conduction band.
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), p. 1–15. doi: 10.1063/1.5117288. Full text in Research Archive Show summary
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.
Berland, Kristian; Chakraborty, Debajit & Thonhauser, Timo (2019). van der Waals density functional with corrected C6 coefficients. Physical review B (PRB). ISSN 2469-9950. 99(19), p. 1–12. doi: 10.1103/PhysRevB.99.195418. Full text in Research Archive Show summary
The nonlocal van der Waals density functional (vdW-DF) has had tremendous success since its inception in 2004 due to its constraint-based formalism that is rigorously derived from a many-body starting point. However, while vdW-DF can describe binding energies and structures for van der Waals complexes and mixed systems with good accuracy, one long-standing criticism—also since its inception—has been that the C 6 coefficients that derive from the vdW-DF framework are largely inaccurate and can be wrong by more than a factor of 2. It has long been thought that this failure to describe the C 6 coefficients is a conceptual flaw of the underlying plasmon framework used to derive vdW-DF. We prove here that this is not the case and that accurate C 6 coefficients can be obtained without sacrificing the accuracy at binding separations from a modified framework that is fully consistent with the constraints and design philosophy of the original vdW-DF formulation. Our design exploits a degree of freedom in the plasmon-dispersion model ω q , modifying the strength of the long-range van der Waals interaction and the crossover from long to short separations, with additional parameters tuned to reference systems. Testing the new formulation for a range of different systems, we not only confirm the greatly improved description of C 6 coefficients, but we also find excellent performance for molecular dimers and other systems. The importance of this development is not necessarily that particular aspects such as C 6 coefficients or binding energies are improved, but rather that our finding opens the door for further conceptual developments of an entirely unexplored direction within the exact same constrained-based nonlocal framework that made vdW-DF so successful in the first place.
Guzik, Matylda N.; Schrade, Matthias; Tofan, Raluca; Almeida Carvalho, Patricia; Berland, Kristian & Sørby, Magnus Helgerud [Show all 9 contributors for this article] (2019). Long- and short-range structures of Ti1-xHfxNi1.0/1.1Sn half-Heusler compounds and their electric transport properties. CrysteEngComm. ISSN 1466-8033. 21, p. 3330–3342. doi: 10.1039/c9ce00046a. Full text in Research Archive
Løvvik, Ole Martin & Berland, Kristian (2018). Predicting the thermoelectric figure-of-merit from first principles. Materials Today: Proceedings. ISSN 2214-7853. 5(4), p. 10227–10234. doi: 10.1016/j.matpr.2017.12.269.
Abu Hamed, Tareq; Adamovic, Nadja; Aeberhard, Urs; Alonso-Alvarez, Diego; Amin-Akhlaghi, Zoe & Auf der Maur, Matthias [Show all 82 contributors for this article] (2018). Multiscale in modelling and validation for solar photovoltaics. EPJ Photovoltaics. ISSN 2105-0716. 9. doi: 10.1051/epjpv/2018008.
Zamulko, Sergii; Berland, Kristian & Persson, Clas (2018). Optical properties of Cu2ZnSn(S(x)Se(1-x))4 by first-principles calculations. Physica Status Solidi (a) applications and materials science. ISSN 1862-6300. 215(17), p. 1–7. doi: 10.1002/pssa.201700945. Full text in Research Archive
Berland, Kristian & Persson, Clas (2018). Thermoelectric transport of GaAs, InP, and PbTe: Hybrid functional with kp interpolation versus scissor-corrected generalized gradient approximation. Journal of Applied Physics. ISSN 0021-8979. 123. doi: 10.1063/1.5030395. Full text in Research Archive
Schrade, Matthias; Berland, Kristian; Eliassen, Simen Nut Hansen; Guzik, Matylda Natalia; Echevarria-Bonet, Cristina & Sørby, Magnus Helgerud [Show all 13 contributors for this article] (2017). The role of grain boundary scattering in reducing the thermal conductivity of polycrystalline XNiSn (X=Hf, Zr, Ti) half-Heusler alloys. Scientific Reports. ISSN 2045-2322. 7. doi: 10.1038/s41598-017-14013-8. Full text in Research Archive
Schröder, Elsebeth; Cooper, Valentino R; Berland, Kristian; Lundqvist, Bengt I; Hyldgaard, Per & Thonhauser, T (2017). The vdW-DF Family of Non-Local Exchange-Correlation Functionals. In Otero de la Roza, Gino & DiLabio, Gino (Ed.), Non-covalent Interactions in Quantum Chemistry and Physics. Elsevier. ISSN 9780128098356. doi: 10.1016/b978-0-12-809835-6.00009-8.
Berland, Kristian; Jiao, Yiao; Lee, Jung-Hoon; Rangel, Tonatiuh; Neaton, Jeffrey B. & Hyldgaard, Per (2017). Assessment of two hybrid van der Waals density functionals for covalent and non-covalent binding of molecules. Journal of Chemical Physics. ISSN 0021-9606. 146(23). doi: 10.1063/1.4986522. Full text in Research Archive
Eliassen, Simen Nut Hansen; Katre, Anikta; Madsen, Georg; Persson, Clas; Løvvik, Ole Martin & Berland, Kristian (2017). Lattice thermal conductivity of TixZryHf1−x−yNiSn half-Heusler alloys calculated from first principles: Key role of nature of phonon modes. Physical review B (PRB). ISSN 2469-9950. 95(4). doi: 10.1103/PhysRevB.95.045202. Full text in Research Archive Show summary
In spite of their relatively high lattice thermal conductivity κℓ, the XNiSn (X=Ti, Zr, or Hf) half-Heusler compounds are good thermoelectric materials. Previous studies have shown that κℓ can be reduced by sublattice alloying on the X site. To cast light on how the alloy composition affects κℓ, we study this system using the phonon Boltzmann-transport equation within the relaxation time approximation in conjunction with density functional theory. The effect of alloying through mass-disorder scattering is explored using the virtual crystal approximation to screen the entire ternary TixZryHf1−x−yNiSn phase diagram. The lowest lattice thermal conductivity is found for the TixHf1−xNiSn compositions; in particular, there is a shallow minimum centered at Ti0.5Hf0.5NiSn with κℓ taking values between 3.2 and 4.1 W/mK when the Ti content varies between 20% and 80%. Interestingly, the overall behavior of mass-disorder scattering in this system can only be understood from a combination of the nature of the phonon modes and the magnitude of the mass variance. Mass-disorder scattering is not effective at scattering acoustic phonons of low energy. By using a simple model of grain boundary scattering, we find that nanostructuring these compounds can scatter such phonons effectively and thus further reduce the lattice thermal conductivity; for instance, Ti0.5Hf0.5NiSn with a grain size of L=100 nm experiences a 42% reduction of κℓ compared to that of the single crystal.
Berland, Kristian & Persson, Clas (2017). Enabling accurate first-principle calculations of electronic properties with a corrected kp scheme. Computational Materials Science. ISSN 0927-0256. 134, p. 17–24. doi: 10.1016/j.commatsci.2017.03.017.
Boström, Mathias; Malyi, Oleksandr; Thiyam, Priyadarshini; Berland, Kristian; Brevik, Iver Håkon & Persson, Clas [Show all 7 contributors for this article] (2016). The influence of Lifshitz forces and gas on premelting of ice within porous materials. Europhysics letters. ISSN 0295-5075. 115(1). doi: 10.1209/0295-5075/115/13001. Full text in Research Archive
Rangel, Tonatiuh; Berland, Kristian; Sharifzadeh, Sahar; Brown-Altvater, Florian; Lee, Kyuho & Hyldgaard, Per [Show all 8 contributors for this article] (2016). Structural and excited-state properties of oligoacene crystals from first principles. Physical Review B. Condensed Matter and Materials Physics. ISSN 1098-0121. 93(11). doi: 10.1103/PhysRevB.93.115206.
Berland, Kristian; Song, Xin; Carvalho, Patricia; Persson, Clas; Finstad, Terje & Løvvik, Ole Martin (2016). Enhancement of thermoelectric properties by energy filtering: Theoretical potential and experimental reality in nanostructured ZnSb. Journal of Applied Physics. ISSN 0021-8979. 119(12). doi: 10.1063/1.4944716. Full text in Research Archive Show summary
Energy filtering has been suggested by many authors as a means to improve thermoelectric properties. The idea is to filter away low-energy charge carriers in order to increase Seebeck coefficient without compromising electronic conductivity. This concept was investigated in the present paper for a specific material (ZnSb) by a combination of first-principles atomic-scale calculations, Boltzmann transport theory, and experimental studies of the same system. The potential of filtering in this material was first quantified, and it was as an example found that the power factor could be enhanced by an order of magnitude when the filter barrier height was 0.5 eV. Measured values of the Hall carrier concentration in bulk ZnSb were then used to calibrate the transport calculations, and nanostructured ZnSb with average grain size around 70 nm was processed to achieve filtering as suggested previously in the literature. Various scattering mechanisms were employed in the transport calculations and compared with the measured transport properties in nanostructured ZnSb as a function of temperature. Reasonable correspondence between theory and experiment could be achieved when a combination of constant lifetime scattering and energy filtering with a 0.25 eV barrier was employed. However, the difference between bulk and nanostructured samples was not sufficient to justify the introduction of an energy filtering mechanism. The reasons for this and possibilities to achieve filtering were discussed in the paper.
Berland, Kristian; Cooper, Valentino R; Lee, Kyuho; Schröder, Elsebeth; Thonhauser, T & Hyldgaard, Per [Show all 7 contributors for this article] (2015). van der Waals forces in density functional theory: a review of the vdW-DF method. Reports on progress in physics (Print). ISSN 0034-4885. 78(6). doi: 10.1088/0034-4885/78/6/066501.
Thonhauser, T.; Zuluaga, S.; Carter, C. A.; Berland, Kristian; Schröder, Elsebeth & Hyldgaard, Per (2015). Spin Signature of Nonlocal Correlation Binding in Metal-Organic Frameworks. Physical Review Letters. ISSN 0031-9007. 115(13). doi: 10.1103/PhysRevLett.115.136402.

View all works in Cristin

Sødahl, Elin Dypvik; Carrete, Jesús; Madsen, Georg & Berland, Kristian (2023). Molecular Rotations in Plastic Crystals: a Machine-Learned Force-Fields Study.
Seyedraoufi, Seyedmojtaba; Day, Graeme M. & Berland, Kristian (2023). Engineering new organic proton-transfer acid-base (anti-)ferroelectric cocrystals using crystal structure prediction.
Berland, Kristian; Seyedraoufi, Seyedmojtaba & Day, Graeme M. (2023). Designing new organic proton-transfer ferroelectrics using crystal structure prediction.
Tranås, Rasmus André; Løvvik, Ole Martin & Berland, Kristian (2023). Screening of low lattice thermal conductivity materials using active learning.
Sødahl, Elin Dypvik; Walker, Julian Bradley; Seyedraoufi, Seyedmojtaba; Görbitz, Carl Henrik & Berland, Kristian (2022). Ferroelectric molecular crystals – Discovering and modeling of unknown properties in known materials .
Sødahl, Elin Dypvik; Walker, Julian; Tranås, Rasmus André & Berland, Kristian (2022). Molecular Ferroelectric Crystals.
Sødahl, Elin Dypvik; Seyedraoufi, Seyedmojtaba; Görbitz, Carl Henrik & Berland, Kristian (2022). Molecular ferroelectric crystals: Discovering new sustainable ferroelectrics .
Sødahl, Elin Dypvik; Walker, Julian & Berland, Kristian (2022). Piezoelectric Response of Plastic Ionic Molecular Crystals: Role of Molecular Rotation.
Sødahl, Elin Dypvik; Walker, Julian & Berland, Kristian (2022). Rotationally-driven piezoelectricity for energy harvesting: Computational study of plastic ionic molecular crystals.
Berland, Kristian; Sødahl, Elin Dypvik & Tranås, Rasmus André (2022). Thermal transport & phase-change properties from first-principles made feasible with machine learning .
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 .
Seyedraoufi, Seyedmojtaba; Sødahl, Elin Dypvik; Berland, Kristian & Gørbitz, Carl Henrik (2022). Database mining and first-principles assessment of organic proton-transfer molecular ferroelectrics.
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.
Sødahl, Elin Dypvik; Görbitz, Carl Henrik & Berland, Kristian (2021). Mining the Cambridge Structural Database for substituted structures to guide rational design of organic molecular crystals.
Tranås, Rasmus André; Løvvik, Ole Martin; Tomic, Oliver & Berland, Kristian (2021). Active sample selection for finding low lattice thermal conductivity materials using machine learning .
Berland, Kristian; Chakraborty, Debajit; Jenkins, Trevor & Thonhauser, Timo (2021). Next generation nonlocal van der waals functionals.
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; Berland, Kristian; Remonato, Filippo; Sagvolden, Espen; Flage-Larsen, Espen & Schrade, Matthias [Show all 13 contributors for this article] (2019). Screening thermoelectric materials with ab initio atomistic modelling and machine learning techniques.
Boström, Mathias; Thiyam, Priydarshini; Fiedler, Johannes; Persson, Clas; Berland, Kristian & Buhmann, Stefan Yoshi [Show all 9 contributors for this article] (2018). A habitat for life.
Berland, Kristian (2018). van der Waals density functional theory. Show summary
van der Waals density functional theory: Dispersion forces in density functional theory For a long time, lack of dispersion forces was a hallmark shortcoming of DFT, but this has been resolved during the last 15 years. In this early Saturday lecture, I will discuss the exchange-correlation functional of DFT in more detail and explain what physical effects can be described at different level of theory. I will next outline various approaches to include dispersion forces in DFT calculations. One of the most successful and robust methods for describing these forces in DFT is the Chalmers-Rutgers van der Waals density functional (vdW-DF). I will outline a derivation of the van der Waals density functional (vdW-DF) and connect it earlier developments such as the Anderson-Langreht-Lundqvist (ALL) functional. For the latest theoretical developments within vdW-DF, I refer to topics covered in my workshop talk. van der Waals density functional theory: Applications In this lecture, I will provide several examples of how DFT using vdW-DF and related methods has provided insight into van der Waals binding at the nanoscale. In particular, many important systems are characterized by a competition between chemical bonding and non-covalent interactions, challenging the textbook notion that van der Waals forces are ‘weak’ and can be disregarded for covalently-bonded systems. I will also exemplify cases where different vdW-DF variants and related methods give qualitative contradicting predictions, highlighting why care much be taken when selecting the most appropriate vdW inclusive DFT method. Shortcomings of vdW-DF beyond typical binding separations will also be discussed, such as incorrect power asymptotic laws for certain systems and geometries.
Berland, Kristian (2018). Electronic and optical properties in density functional theory and beyond. Show summary
Density functional theory (DFT) is a formally exact theory, in which the total energy is a functional of the electronic density n(r). In the Kohn Sham theory, which is the most common realization of DFT, the electronic density is described in terms of mean-field “independent particle” Kohn-sham orbitals residing in an effective one-particle potential determined by n(r). Many-particle effects are accounted for in an effective manner through an exchange-correlation (xc) functional. Striking a good balance between accuracy and speed, successive developments of DFT has made the method the by far most widely used theoretical method to obtain atom-level insight and “hard numbers” on electronic, structural, and energetic properties of materials and chemical processes. DFT finds usage in condensed matter physics, chemistry, and increasingly in adjacent fields such as geology and biology. DFT lends itself to studies of van der Waals bonded material at the microscopic level by using van-der Waals inclusive xc-functionals. For macroscopic systems beyond reach of standard DFT implementation (which is typically limited to around 1000 atoms) or in conceptual studies, an alternative is to generate dielectric functionals or polarizabilities of materials and molecules without relying on empirical experimental data and use these as input to Casimir-Lifschitz theory In the final Friday lecture, I will introduce basic concepts of DFT with emphasis on electronic and dielectric properties in the Kohn-Sham formalism. Calculation of the dielectric functional in the in the independent particle approximation will be discussed in detail, followed by an overview of how effects such as local-field effects and two-particle ‘excitonic’ effects can be accounted for by going beyond DFT using many-particle perturbation theory.
Berland, Kristian; Chakraborty, Debajit & Thonhauser, T (2018). Recent developments in van der Waals density functional theory and its future.
Berland, Kristian (2018). Accelerated discovery of new materials.
Berland, Kristian (2018). Strategies to improve thermoelectric transport: Insights from first-principle studies on Half Heuslers.
Berland, Kristian (2018). Non-local correlation functionals: Asymptotics versus expansion in GGA.
Berland, Kristian (2018). The van der Waals density functional.
Berland, Kristian; Eliassen, Simen Nut Hansen; Løvvik, Ole Martin; Persson, Clas & Schrade, Matthias (2018). Computational Engineering of Thermoelectric Materials.
Guzik, Matylda N.; Schrade, Matthias; Tofan, Raluca; Berland, Kristian; Gunnæs, Anette Eleonora & Persson, Clas [Show all 8 contributors for this article] (2017). Structural Investigation of Ti1-xHfxNiySn Half-Heusler Compounds.
Løvvik, Ole Martin; Shulumba, Nina; Hellman, Olle; Persson, Clas & Berland, Kristian (2017). Predicted figure-of-merit of half-Heusler alloys - importance of scattering mechanisms.
Schrade, Matthias; Berland, Kristian; Guzik, Matylda Natalia; Løvvik, Ole Martin & Finstad, Terje (2017). Why does the thermal conductivity of XNiSn vary for nominally identical samples?
Zamulko, Sergii; Chen, Rongzhen; Berland, Kristian & Persson, Clas (2017). First-principles analysis of Cu2Zn(Sn,Si/Ge)(S/Se)4 and Cu2ZnSn(S,Se)4 alloys.
Zamulko, Sergii; Berland, Kristian; Li, Shu-yi; Platzer-Björkman, Charlotte & Persson, Clas (2017). Theoretical and experimental analysis of optical properties of Cu2ZnSn(S,Se)4solar absorbers.
Berland, Kristian; Zamulko, Sergii & Persson, Clas (2017). Comparison of hybrid functional and GGA for transport and excited-state properties of bulk semiconductors.
Berland, Kristian (2017). Perspectives on van der Waals functionals.
Berland, Kristian & Persson, Clas (2017). Computing accurate dielectric functions and transport properties of semiconductors with help of a new k.p based interpolation scheme.
Berland, Kristian & Persson, Clas (2017). The need for dense Brillouin zone sampling in transport and optical calculations... and how to deal with it.
Berland, Kristian; Løvvik, Ole Martin & Persson, Clas (2017). How hybrid exchange affects thermoelectric transport properties of GaAs, PbTe, Cu2Se, and half Heuslers: Accurate grid sampling enabled with a corrected k.p scheme.
Berland, Kristian; Zamulko, Sergii & Persson, Clas (2017). Resolving fine features of the dielectric function: Computational issues and opportunities.
Berland, Kristian; Eliassen, Simen Nut Hansen; Schrade, Matthias; Tofan, Raluca; Guzik, Matylda Natalia & Gunnæs, Anette Eleonora [Show all 11 contributors for this article] (2017). Using theory to understand thermoelectric materials.
Berland, Kristian; Persson, Clas & Tomic, Stanko (2016). STSM Report: Connecting the ab initio atomistic with continuum modeling: parameterization.
Berland, Kristian; Eliassen, Simen Nut Hansen; Katre, Anikta; Madsen, Georg; Persson, Clas & Løvvik, Ole Martin (2016). How to bring down the thermal conductivity of MNiSn Half-Heuslers - a theoretical analysis .
Zamulko, Sergii; Berland, Kristian; Platzer-Björkman, Charlotte & Persson, Clas (2016). First-principles analysis of Cu2ZnSn(S,Se)4 alloys for solar cell application .
Løvvik, Ole Martin; Eliassen, Simen Nut Hans; Berland, Kristian; Song, Xin; Schrade, Matthias & Shulumba, N. [Show all 9 contributors for this article] (2016). Predicting the thermoelectric figure of merit from first principles.
Schrade, Matthias; Echevarria-Bonet, Cristina; Eliassen, Simen Nut Hansen; Berland, Kristian; Persson, Clas & Tofan, Raluca [Show all 9 contributors for this article] (2016). Thermal Properties of XNiSn(X = Hf, Zr, Ti) half Heusler Alloys.
Schrade, Matthias; Echevarria-Bonet, Cristina; Guzik, Matylda Natalia; Tofan, Raluca; Gunnæs, Anette Eleonora & Eliassen, Simen Nut Hansen [Show all 10 contributors for this article] (2016). Thermal properties of XNiSN (X = Ti, Zr, Hf) half Heusler alloys.
Tofan, Raluca; Echevarria-Bonet, Cristina; Berland, Kristian; Schrade, Matthias; Sørby, Magnus Helgerud & Hauback, Bjørn Christian [Show all 10 contributors for this article] (2016). The effect of spark plasma sintering on structure and phase stability in half-Heusler thermoelectric alloys.
Berland, Kristian & Persson, Clas (2016). A corrected k.p scheme for accurate electronic properties .
Berland, Kristian; Eliassen, Simen Nut Hansen; Katre, A; Madsen, Georg; Løvvik, Ole Martin & Persson, Clas (2016). Optimizing the thermoelectric properties of (TiHfZr)NiSn alloys.
Tofan, Raluca; Echevarria-Bonet, Cristina; Berland, Kristian; Schrade, Matthias; Sørby, Magnus Helgerud & Hauback, Bjørn Christian [Show all 10 contributors for this article] (2016). Microstructural characterization of spark plasma sintered (X,X’)NiSn half‐Heusler alloys.
Berland, Kristian & Persson, Clas (2016). Enabling accurate transport calculations with a k.p-method based interpolation scheme: Applications to thermoelectric properties.
Løvvik, Ole Martin; Eliassen, Simen Nut Hansen; Berland, Kristian & Peters, Thijs (2016). Transport in materials – understanding the motion of electrons, atoms, and phonons.
Løvvik, Ole Martin; Eliassen, Simen Nut Hansen; Berland, Kristian & Peters, Thijs (2016). Transport properties of functional materials – understanding the motion of electrons, atoms, and phonons.
Løvvik, Ole Martin; Eliassen, Simen Nut Hansen & Berland, Kristian (2016). Transport calculations of thermoelectric materials from first principles.
Løvvik, Ole Martin; Eliassen, Simen Nut Hansen; Berland, Kristian; Flage-Larsen, Espen; Jensen, Ingvild Julie Thue & Peters, Thijs [Show all 7 contributors for this article] (2015). Transport Properties of Materials from First Principles.
Berland, Kristian; Lindberg, Per Filip & Persson, Clas (2015). Solceller kommer til å være overalt. Aftenposten Viten. ISSN 2464-3033.
Berland, Kristian; Lee, Kyuho; Sharifzadeh, Sahar & Neaton, Jeffrey B. (2015). Electronic and optical properties of a metal-organic framework with ab initio many-body perturbation theory.
Hyldgaard, Per; Berland, Kristian & Schröder, Elsebeth (2015). A van der Waals density functional built upon the electron-gas foundation.
Gordillo, Tonatiuh Rangel; Sharifzadeh, Sahar; Berland, Kristian; Altvater, Florian; Lee, Kyuho & Hyldgaard, Per [Show all 8 contributors for this article] (2015). Van der Waals Dispersion Interactions and Excited States of Oligoacene Molecular Crystals.
Eliassen, Simen Nut Hansen; Berland, Kristian & Løvvik, Ole Martin (2015). FIRST PRINCIPLE CALCULATIONS OF THERMAL CONDUCTIVITY IN HALF-HEUSLER COMPOUNDS.
Løvvik, Ole Martin; Eliassen, Simen Nut Hansen; Berland, Kristian; Peters, Thijs & Song, Xin (2015). Nanostructures for energy applications - a brief tour of activities in 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. Show summary
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.
Eliassen, Simen Nut Hansen; Berland, Kristian & Løvvik, Ole Martin (2016). A first principles study of lattice thermal conductivity in XNiSn (X = Ti, Zr, Hf) half-Heusler alloys for thermoelectric applications. UiP.