Ponniah Ravindran

• Augustine, Anu Maria & Ponniah, Ravindran (2020). Role of W-site substitution on mechanical and electronic properties of cubic tungsten carbide. Journal of Physics: Condensed Matter.  ISSN 0953-8984.  32(14) . doi: 10.1088/1361-648X/ab6428
• Augustine, Anu Maria; Sudarsanan, Vishnu; Patra, Lokanath; Kavitha, Mary, J. & Ponniah, Ravindran (2019). Li-rich Li6MnxFe(1-x)S4 as cathode material for Li-ion battery. AIP Conference Proceedings.  ISSN 0094-243X.  2115(1) . doi: 10.1063/1.5113462
• Christhunathan, Vivek; Augustine, Anu Maria; Sudarsanan, Vishnu; Vairamoorthy, N & Ponniah, Ravindran (2019). Ab-initio modelling of new cathode material for Li-ion battery based on the Ti substituted Li2Fe(SO4)2. AIP Conference Proceedings.  ISSN 0094-243X.  2115 . doi: 10.1063/1.5113447
• Kiruthika, S.; Varunaa, R & Ponniah, Ravindran (2019). Amphoteric behavior of hydrogen in bimetallic molecular like hydrides. AIP Conference Proceedings.  ISSN 0094-243X.  2115 . doi: 10.1063/1.5113393
• Kishore, M. R. Ashwin; Sjåstad, Anja Olafsen & Ponniah, Ravindran (2019). Influence of hydrogen and halogen adsorption on the photocatalytic water splitting activity of C2N monolayer: A first-principles study. Carbon.  ISSN 0008-6223.  141, s 50- 58 . doi: 10.1016/j.carbon.2018.08.072
• Kruthika, G; Ponniah, Ravindran & Murugan, Palanichamy (2019). Effect of anionic and cationic substitutions on the magnetic property of hydrated α-MnO2. AIP Conference Proceedings.  ISSN 0094-243X.  2115(1) . doi: 10.1063/1.5113329
• Ravindran, Varunaa & Ponniah, Ravindran (2019). Potential hydrogen storage materials from metal decorated 2D-C2N: An: ab initio study. Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  21(45), s 25311- 25322 . doi: 10.1039/c9cp05105h
• Sreedevi, P. D.; Ponniah, Ravindran & Vidya, R. (2019). First principles prediction of the ground state crystal structures of antiperovskite compounds A3PN (A= Be, Mg, Ca, Sr, Ba and Zn). Materials Today: Proceedings.  ISSN 2214-7853.  8, s 294- 300 . doi: 10.1016/j.matpr.2019.02.114
• Sreedevi, P. D.; Vidya, Ravindran & Ponniah, Ravindran (2019). Earth-abundant nontoxic direct band gap semiconductors for photovoltaic applications by ab-initio simulations. Solar Energy.  ISSN 0038-092X.  190, s 350- 360 . doi: 10.1016/j.solener.2019.08.011
• Varunaa, R; Fjellvåg, Helmer & Ponniah, Ravindran (2019). Zinc substituted MgH2 - a potential material for hydrogen storage applications. International Journal of Hydrogen Energy.  ISSN 0360-3199.  44(26), s 13632- 13646 . doi: 10.1016/j.ijhydene.2019.04.016
• Varunaa, R; Kiruthika, S. & Ponniah, Ravindran (2019). Ti4+ substituted magnesium hydride as promising material for hydrogen storage and photovoltaic applications. AIP Conference Proceedings.  ISSN 0094-243X.  2115 . doi: 10.1063/1.5113384
• Augustine, Anu Maria; Sudarsanan, Vishnu; Sunny, Geo & Ponniah, Ravindran (2018). A first principle study on iron substituted LiNi (BO3) to use as cathode material for Li-ion batteries. AIP Conference Proceedings.  ISSN 0094-243X.  1942:090043 . doi: 10.1063/1.5028958
• Choudhary, Mukesh K. & Ponniah, Ravindran (2018). Effect of multinary substitution on electronic and transport properties of TiCoSb based half-Heusler alloys. AIP Conference Proceedings.  ISSN 0094-243X.  1953:110024 . doi: 10.1063/1.5033049
• Choudhary, Mukesh K. & Ponniah, Ravindran (2018). Search for thermoelectrics with high figure of merit in half-Heusler compounds with multinary substitution. AIP Conference Proceedings.  ISSN 0094-243X.  1942(1) . doi: 10.1063/1.5029029
• Kiruthika, Srinu & Ponniah, Ravindran (2018). Chemical bonding analysis on amphoteric hydrogen - Alkaline earth ammine borohydrides. AIP Conference Proceedings.  ISSN 0094-243X.  1942:140040 . doi: 10.1063/1.5029171
• Kishore, M. R. Ashwin & Ponniah, Ravindran (2018). Phosphorene-AsP heterostructure as a potential excitonic solar cell material - A first principles study. AIP Conference Proceedings.  ISSN 0094-243X.  1942 . doi: 10.1063/1.5029207
• Patra, Lokanath; Pan, Zhao; Chen, Jun; Azuma, Masaki & Ponniah, Ravindran (2018). Metamagnetism stabilized giant magnetoelectric coupling in ferroelectric xBaTiO3–(1 − x)BiCoO3 solid solution. Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  20(10), s 7021- 7032 . doi: 10.1039/c7cp07677k
• Patra, Lokanath & Ponniah, Ravindran (2018). Magnetoelectric properties of Pb free Bi2FeTiO6: A theoretical investigation. AIP Conference Proceedings.  ISSN 0094-243X.  1953 . doi: 10.1063/1.5033104
• Patra, Lokanath & Ponniah, Ravindran (2018). Theoretical investigation of the magnetoelectric properties of Bi2NiTiO6. AIP Conference Proceedings.  ISSN 0094-243X.  1942:130054 . doi: 10.1063/1.5029124
• Ashwin Kishore, MR & Ponniah, Ravindran (2017). Tailoring the Electronic Band Gap and Band Edge Positions in the C2N Monolayer by P and As Substitution for Photocatalytic Water Splitting. Journal of Physical Chemistry C.  ISSN 1932-7447.  121(40), s 22216- 22224 . doi: 10.1021/acs.jpcc.7b07776
• Kishore, M. R. Ashwin & Ponniah, Ravindran (2017). Te doped indium (II) selenide photocatalyst for water splitting: A first principles study. AIP Conference Proceedings.  ISSN 0094-243X.  1832 . doi: 10.1063/1.4980582
• M R, Ashwin Kishore & Ponniah, Ravindran (2017). Enhanced photocatalytic water splitting in C2N monolayer by C-site isoelectronic substitution. ChemPhysChem.  ISSN 1439-4235.  18(12), s 1526- 1532 . doi: 10.1002/cphc.201700165
• Patra, Lokanath & Ponniah, Ravindran (2017). Prediction of magnetoelectric behavior in Bi2MnTiO6. AIP Conference Proceedings.  ISSN 0094-243X.  1832 . doi: 10.1063/1.4980773
• Varunaa, R & Ponniah, Ravindran (2017). Phase Stability, Phase Mixing, and Phase Separation in Fluorinated Alkaline Earth Hydrides. Journal of Physical Chemistry C.  ISSN 1932-7447.  121(40), s 21806- 21820 . doi: 10.1021/acs.jpcc.7b03265
• Varunaa, R & Ponniah, Ravindran (2017). Structural phase stability in fluorinated calcium hydride. AIP Conference Proceedings.  ISSN 0094-243X.  1832 . doi: 10.1063/1.4980184
• Kishore, M. R. Ashwin; Okamoto, Hiroshi; Patra, Lokanath; Vidya, Ravindran; Sjåstad, Anja Olafsen; Fjellvåg, Helmer & Ponniah, Ravindran (2016). Theoretical and experimental investigation on structural, electronic and magnetic properties of layered Mn5O8. Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  18(40), s 27885- 27896 . doi: 10.1039/c6cp04170a
• Lokanath, Patra; M R, Ashwin Kishore; R, Vidya; Anja O, Sjåstad; H, Fjellvåg & Ponniah, Ravindran (2016). Electronic and magnetic structures of hole doped trilayer La4-xSrxNi3O8 from first principles calculations. Inorganic Chemistry.  ISSN 0020-1669.  55, s 11898- 11907
• M R, Ashwin Kishore; H, Okamoto; Lokanath, Patra; R, Vidya; Anja O, Sjåstad; H, Fjellvåg & Ponniah, Ravindran (2016). Theoretical and experimental investigation on structural, electronic, and magnetic properties of layered Mn5O8. Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  18, s 27885- 27896
• Patra, Lokanath; Kishore, M. R. Ashwin; Vidya, Ravindran; Sjåstad, Anja Olafsen; Fjellvåg, Helmer & Ponniah, Ravindran (2016). Electronic and magnetic structures of hole doped trilayer La4-xSrxNi3O8 from first-principles calculations. Inorganic Chemistry.  ISSN 0020-1669.  55(22), s 11898- 11907 . doi: 10.1021/acs.inorgchem.6b01938
• Iozzi, Maria Francesca; Vajeeston, Ponniah; Vidya, R.; Ravindran, Ponniah & Fjellvåg, Helmer (2015). Structural and electronic properties of transparent conducting delafossite: a comparison between the AgBO2 and CuBO2 families (B = Al, Ga, In and Sc, Y). RSC Advances.  ISSN 2046-2069.  5(2), s 1366- 1377 . doi: 10.1039/c3ra47531j
• Manimuthu, P.; Vidya, R.; Ravindran, Ponniah; Fjellvåg, Helmer & Venkateswaran, C. (2015). Observation of direct magneto-dielectric behaviour in Lu3Fe5O12−δ above room-temperature. Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  17(27), s 17688- 17698 . doi: 10.1039/c5cp02719e
• Yang, Li-Ming; Ravindran, Ponniah & Tilset, Mats (2013). Solid-State Structure and Calculated Electronic Structure, Formation Energy, Chemical Bonding, and Optical Properties of Zn4O(FMA)(3) and Its Heavier Congener Cd4O(FMA)(3). Inorganic Chemistry.  ISSN 0020-1669.  52(8), s 4217- 4228 . doi: 10.1021/ic301928a
• Yang, Li-Ming; Ravindran, Ponniah; Vajeeston, Ponniah; Svelle, Stian & Tilset, Mats (2013). A quantum mechanically guided view of Cd-MOF-5 from formation energy, chemical bonding, electronic structure, and optical properties. Microporous and Mesoporous Materials.  ISSN 1387-1811.  175, s 50- 58 . doi: 10.1016/j.micromeso.2013.03.020
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2012). Prediction of structural, lattice dynamical, and mechanical properties of CaB2. RSC Advances.  ISSN 2046-2069.  2(31), s 11687- 11694 . doi: 10.1039/c2ra21807k
• Vajeeston, Ponniah; Sartori, Sabrina; Ravindran, Ponniah; Knudsen, Kenneth; Hauback, Bjørn & Fjellvåg, Helmer (2012). MgH2 in Carbon Scaffolds: A Combined Experimental and Theoretical Investigation. Journal of Physical Chemistry C.  ISSN 1932-7447.  116(40), s 21139- 21147 . doi: 10.1021/jp3008199
• Vidya, R.; Ravindran, Ponniah & Fjellvåg, Helmer (2012). Ab-initio studies on Li doping, Li-pairs, and complexes between Li and intrinsic defects in ZnO. Journal of Applied Physics.  ISSN 0021-8979.  111(12) . doi: 10.1063/1.4729774
• Yang, Li-Ming; Ravindran, Ponniah; Vajeeston, Ponniah & Tilset, Mats (2012). Ab initio investigations on the crystal structure, formation enthalpy, electronic structure, chemical bonding, and optical properties of experimentally synthesized isoreticular metal-organic framework-10 and its analogues: M-IRMOF-10 (M = Zn, Cd, Be, Mg, Ca, Sr and Ba). RSC Advances.  ISSN 2046-2069.  2(4), s 1618- 1631 . doi: 10.1039/c1ra00187f
• Yang, Li-Ming; Ravindran, Ponniah; Vajeeston, Ponniah & Tilset, Mats (2012). Formation of an intermediate band in isoreticular metal-organic framework-993 (IRMOF-993) and metal-substituted analogues M-IRMOF-993. Journal of Materials Chemistry.  ISSN 0959-9428.  22(32), s 16324- 16335 . doi: 10.1039/c2jm31360j
• Yang, Li-Ming; Ravindran, Ponniah; Vajeeston, Ponniah & Tilset, Mats (2012). Properties of IRMOF-14 and its analogues M-IRMOF-14 (M = Cd, alkaline earth metals): electronic structure, structural stability, chemical bonding, and optical properties. Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  14(14), s 4713- 4723 . doi: 10.1039/c2cp24091b
• Frommen, Christoph; Sørby, Magnus Helgerud; Ravindran, Ponniah; Vajeeston, Ponniah; Fjellvåg, Helmer & Hauback, Bjørn (2011). Synthesis, crystal structure, and thermal properties of the first mixed-metal and anion-substituted rare earth borohydride LiCe(BH4)3Cl. Journal of Physical Chemistry C.  ISSN 1932-7447.  115(47), s 23591- 23602 . doi: 10.1021/jp205105j Fulltekst i vitenarkiv.
• Karazhanov, Smagul; Ravindran, Ponniah & Grossner, Ulrike (2011). First-principles study on electronic structure, phase stability, and optical properties of In2X2O7 (X= C, Si, Ge or Sn). Thin Solid Films.  ISSN 0040-6090.  519(19), s 6561- 6567 . doi: 10.1016/j.tsf.2011.04.221 Fulltekst i vitenarkiv.
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2011). Phonon, IR, and Raman Spectra, NMR Parameters, and Elastic Constant Calculations for AlH3 Polymorphs. Journal of Physical Chemistry A.  ISSN 1089-5639.  115(39), s 10708- 10719 . doi: 10.1021/jp2011342
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2011). Stability enhancement by particle size reduction in AlH3. Journal of Alloys and Compounds.  ISSN 0925-8388.  509, s S662- S666 . doi: 10.1016/j.jallcom.2010.11.110
• Vajeeston, Ponniah; Ravindran, Ponniah; Hauback, Bjørn & Fjellvåg, Helmer (2011). Prediction of crystal structure, lattice dynamical, and mechanical properties of CaB2H2. International Journal of Hydrogen Energy.  ISSN 0360-3199.  36(16), s 10149- 10158 . doi: 10.1016/j.ijhydene.2011.05.038
• Vidya, Ravindran; Ravindran, Ponniah; Fjellvåg, Helmer; Svensson, Bengt Gunnar; Monakhov, Edouard; Ganchenkova, Maria & Nieminen, Risto G. (2011). Energetics of intrinsic defects and their complexes in ZnO investigated by density functional calculations. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  83(4) . doi: 10.1103/PhysRevB.83.045206
• Yang, Li-Ming; Vajeeston, Ponniah; Ravindran, Ponniah; Fjellvåg, Helmer & Tilset, Mats (2011). Revisiting isoreticular MOFs of alkaline earth metals: a comprehensive study on phase stability, electronic structure, chemical bonding, and optical properties of A-IRMOF-1 (A = Be, Mg, Ca, Sr, Ba). Physical Chemistry, Chemical Physics - PCCP.  ISSN 1463-9076.  13(21), s 10191- 10203 . doi: 10.1039/c0cp02944k
• Karazhanov, Smagul & Ravindran, Ponniah (2010). Ab Initio Study Of Double Oxides ZnX2O4 (X=Al, Ga, In) Having Spinel Structure. Journal of The American Ceramic Society.  ISSN 0002-7820.  93(10), s 3335- 3341 . doi: 10.1111/j.1551-2916.2010.03864.x
• Sæterli, Ragnhild; Selbach, Sverre Magnus; Ravindran, Ponniah; Grande, Tor & Holmestad, Randi (2010). Electronic structure of multiferroic BiFeO3 and related compounds: Electron energy loss spectroscopy and density functional study. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  82(6) . doi: 10.1103/PhysRevB.82.064102
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2010). Nono-structures of NaBH4 and KBH4. Journal of Nanoscience and Nanotechnology.  ISSN 1533-4880.  11(3), s 2296- 2318 . doi: 10.1166/jnn.2010.3517
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2010). Structural investigation and thermodynamical properties of alkali calcium trihydrides. Journal of Chemical Physics.  ISSN 0021-9606.  132(11) . doi: 10.1063/1.3299732
• Yang, Li-Ming; Vajeeston, Ponniah; Ravindran, Ponniah; Fjellvåg, Helmer & Tilset, Mats (2010). Theoretical Investigations on the Chemical Bonding, Electronic Structure, And Optical Properties of the Metal-Organic Framework MOF-5. Inorganic Chemistry.  ISSN 0020-1669.  49(22), s 10283- 10290 . doi: 10.1021/ic100694w
• Karazhanov, Smagul; Ravindran, Ponniah; Fjellvåg, Helmer & Svensson, Bengt Gunnar (2009). Electronic structure and optical properties of ZnSiO3 and Zn2SiO4. Journal of Applied Physics.  ISSN 0021-8979.  106(12) . doi: 10.1063/1.3268445 Fulltekst i vitenarkiv.
• Karazhanov, Smagul; Ravindran, Ponniah; Vajeeston, Ponniah; Ulyashin, AG; Fjellvåg, Helmer & Svensson, Bengt Gunnar (2009). Phase stability and pressure-induced structural transitions at zero temperature in ZnSiO3 and Zn2SiO4. Journal of Physics: Condensed Matter.  ISSN 0953-8984.  21(48) . doi: 10.1088/0953-8984/21/48/485801 Fulltekst i vitenarkiv.
• Karlsen, Ole Bjørn; Kjekshus, Arne; Fjellvåg, Helmer; Ravindran, Ponniah; Vidya, R. & Hauback, BC (2009). Structure and magnetism of the beta-Mn-Co solid-solution phase. Journal of Alloys and Compounds.  ISSN 0925-8388.  476(1-2), s 9- 13 . doi: 10.1016/j.jallcom.2008.09.011
• Klaveness, Arne; Fjellvåg, Helmer; Kjekshus, Arne; Ravindran, Ponniah & Swang, O (2009). A semi-empirical approach to accurate standard enthalpies of formation for solid hydrides. Journal of Alloys and Compounds.  ISSN 0925-8388.  469(1-2), s 617- 622 . doi: 10.1016/j.jallcom.2008.02.060
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2009). Nanostructures of LiBH4: a density-functional study. Nanotechnology.  ISSN 0957-4484.  20(27) . doi: 10.1088/0957-4484/20/27/275704
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2009). Predicting New Materials for Hydrogen Storage Application. Materials.  ISSN 1996-1944.  2, s 2296- 2318 . doi: 10.3390/ma2042296
• Karazhanov, Smagul; Ulyashin, AG; Ravindran, Ponniah & Vajeeston, Ponniah (2008). Semiconducting hydrides. Europhysics letters.  ISSN 0295-5075.  82 . doi: 10.1209/0295-5075/82/17006
• Karazhanov, Smagul; Ulyashin, AG; Vajeeston, Ponniah & Ravindran, Ponniah (2008). Hydrides as materials for semiconductor electronics. Philosophical Magazine.  ISSN 1478-6435.  88, s 2461- 2476 . doi: 10.1080/14786430802360362
• Offernes, Laila; Ravindran, Ponniah; Seim, CW & Kjekshus, Arne (2008). Prediction of composition for stable half-Heusler phases from electronic-band-structure analyses. Journal of Alloys and Compounds.  ISSN 0925-8388.  458, s 47- 60 . doi: 10.1016/j.jallcom.2007.04.038
• Ravindran, Ponniah; Vidya, R.; Eriksson, O & Fjellvåg, Helmer (2008). Magnetic-instability-induced giant magnetoelectric coupling. Advanced Materials.  ISSN 0935-9648.  20, s 1353- + . doi: 10.1002/adma.200701889
• Ravindran, Ponniah; Vidya, R.; Fjellvåg, Helmer & Kjekshus, Arne (2008). Validity of bond-length and Mossbauer parameters to assign oxidation states in multicomponent oxides: Case study of Sr4Fe4O11. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  77 . doi: 10.1103/PhysRevB.77.134448 Vis sammendrag

  From analyses of structural information for oxides with Fe in different oxidn. states and computationally estd. Mossbauer parameters (hyperfine field, isomer shift, and quadrupole splitting) based on d.-functional theory, we show that the charges residing on the different constituents cannot be directly derived either from structural or Mossbauer measurements. We have analyzed charge d., charge transfer, electron localization function, crystal orbital Hamilton population, and partial d. of states to explain the bonding characteristics. Born-effective charge tensor is used to quantify the charges present at the at. sites in Sr4Fe4O11. We show that the effects of covalence are important in explaining the electronic structure, magnetism, and chem. bonding in oxygen-vacancy-ordered systems such as Sr4Fe4O11 and on ignoring covalence, one can be misled in oxidn.-state assignments.

• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2008). Novel High Pressure Phases of beta-AlH3: A Density-Functional Study. Chemistry of Materials.  ISSN 0897-4756.  20(19), s 5997- 6002 . doi: 10.1021/cm800282b
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2008). Structural phase stability studies on MBeH3 (M = Li, Na, K, Rb, Cs) from density functional calculations. Inorganic Chemistry.  ISSN 0020-1669.  47 . doi: 10.1021/ic7015897 Vis sammendrag

  D. functional theory calcns. within the generalized-gradient approxn. are used to establish the ground-state structure, equil. structural parameters, and electronic structure for MBeH3 phases. From the 24 structural arrangements used as inputs for structural optimization calcns., the ground-state crystal structures of MBeH3 phases have been predicted. At ambient conditions, LiBeH3 and NaBeH3 crystallize with perovskite-related orthorhombic and cubic structures, resp. The remaining phases KBeH3, RbBeH3, and CsBeH3 crystallize in a monoclinic structure. In the predicted phases one can store up to 15.93 wt. % of hydrogen. The formation energy for the MBeH3 phases have been investigated along different reaction pathways. The electronic structures reveal that all these phases are insulators with estd. band gaps varying between 1.79 and 3.44 eV.

• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2008). Theoretical investigations on low energy surfaces and nanowires of MgH2. Nanotechnology.  ISSN 0957-4484.  19 . doi: 10.1088/0957-4484/19/27/275704
• Vajeeston, Ponniah; Ravindran, Ponniah; Kjekshus, Arne & Fjellvåg, Helmer (2008). First-principles investigations of the MMgH3 (M = Li, Na, K, Rb, Cs) series. Journal of Alloys and Compounds.  ISSN 0925-8388.  450 . doi: 10.1016/j.jallcom.2006.10.163
• Vidya, R.; Ravindran, Ponniah; Knizek, K; Kjekshus, Arne & Fjellvåg, Helmer (2008). Density functional theory studies of spin, charge, and orbital ordering in YBaT2O5 (T = Mn, Fe, Co). Inorganic Chemistry.  ISSN 0020-1669.  47, s 6608- 6620 . doi: 10.1021/ic702025c Vis sammendrag

  Spin, charge, and orbital orderings are influenced by electron/hole doping, cation radii, oxygen stoichiometry, temp., magnetic field, and so on. In order to understand the role of electron/hole doping, we have studied variations in spin, charge, and orbital ordering in terms of d-band filling for YBaMn2O5, YBaFe2O5, and YBaCo2O5. The calcns. were performed using d. functional theory as implemented in the full-potential linearized APW method. We have carried out calcns. for nonmagnetic, ferromagnetic, and antiferromagnetic configurations. A ferrimagnetic ground state was established for YBaMn2O5, whereas YBaFe2O5 and YBaCo2O5 have antiferromagnetic ground states; all of these results are in agreement with exptl. findings. The effects of spin-orbit coupling, the Hubbard U parameter, and orbital polarization on the magnetic properties were also analyzed. The electronic band characteristics were analyzed using total as well as site- and orbital-projected densities of states. Inclusion of spin-orbit coupling and Coulomb correlation effects in the calcns. was found to be important in order to reproduce the exptl. established semiconducting behaviors of YBaFe2O5 and YBaCo2O5. In order to quantify the charges at each at. site, we made use of the Bader "atom-in-mol." concept and Born effective-charge (BEC) analyses. The structural optimizations and BEC tensor calcns. were performed using the VASP-PAW method. The different types of charge and orbital orderings in these compds. were visualized using the energy-projected d. matrixes of the d electrons. Substantial differences in ordering patterns with respect to d-band filling emerged. Ordering of the dz2 orbital of Mn in YBaMn2O5 gave rise to G-type ferrimagnetic spin ordering along the c direction and checkerboard-type charge ordering, whereas ordering of the dx2-y2 orbital of Fe in YBaFe2O5 caused Wollan-Koehler G-type antiferromagnetic spin ordering along the b direction and stripe-type charge ordering. Similarly, a complex pattern of orbital ordering in YBaCo2O5 activated spin and charge orderings similar to those in YBaFe2O5.

• Yartys, Volodymyr; Vajeeston, Ponniah; Riabov, Alexander Bronoslavovich; Ravindran, Ponniah; Denys, Roman Volodymyrovich; Mæhlen, Jan Petter; Delaplane, Robert G. & Fjellvåg, Helmer (2008). Crystal chemistry and metal-hydrogen bonding in anisotropic and interstitial hydrides of intermetallics of rare earth (R) and transition metals (T), RT3 and R2T7. Zeitschrift fur Kristallographie.  ISSN 0044-2968.  223(10), s 674- 689 . doi: 10.1524/zkri.2008.1030
• Karazhanov, Smagul; Ravindran, Ponniah; Kjekshus, Arne; Fjellvåg, Helmer & Svensson, Bengt Gunnar (2007). Electronic structure and optical properties of ZnX (X=O, S, Se, Te): A density functional study. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  75 . doi: 10.1103/PhysRevB.75.155104
• Karazhanov, Smagul; Ravindran, Ponniah; Vajeeston, Ponniah; Ulyashin, A; Finstad, Terje & Fjellvåg, Helmer (2007). Phase stability, electronic structure, and optical properties of indium oxide polytypes. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  76(7) . doi: 10.1103/PhysRevB.76.075129 Fulltekst i vitenarkiv.
• Karazhanov, Smagul; Ravindran, Ponniah; Vajeeston, Ponniah & Ulyashin, AG (2007). Hydride electronics. Physica status solidi. A, Applied research.  ISSN 0031-8965.  204, s 3538- 3544 Fulltekst i vitenarkiv.
• Klaveness, Arne; Vajeeston, Ponniah; Ravindran, Ponniah; Fjellvåg, Helmer & Kjekshus, Arne (2007). Structure and bonding in BA1H(5) (B = Be, Ca, Sr) from first-principle calculations. Journal of Alloys and Compounds.  ISSN 0925-8388.  433 . doi: 10.1016/j.jallcom.2006.06.047
• Lalitha, S; Karazhanov, Smagul; Ravindran, Ponniah; Senthilarasu, S; Sathyamoorthy, R & Janabergenov, J (2007). Electronic structure, structural and optical properties of thermally evaporated CdTe thin films. Physica. B, Condensed matter.  ISSN 0921-4526.  387, s 227- 238 . doi: 10.1016/j.physb.2006.04.008
• Offernes, Laila; Ravindran, Ponniah & Kjekshus, Arne (2007). Electronic structure and chemical bonding in half-Heusler phases. Journal of Alloys and Compounds.  ISSN 0925-8388.  439, s 37- 54 . doi: 10.1016/j.jallcom.2006.08.316
• Søndenå, Rune; Søndenå, Rune; Stølen, Svein; Ravindran, P.; Ravindran, Ponniah; Grande, Tor & Allan, Neil L. (2007). Corner- versus face-sharing octahedra in AMnO3 perovskites (A=Ca, Sr, and Ba). Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  75, s 184105-1- 184105-10 . doi: 10.1103/PhysRevB.75.184105
• Søndenå, Rune; Søndenå, Rune; Stølen, Svein; Ravindran, Ponniah; Ravindran, P. & Grande, Tor (2007). Heat capacity and lattice dynamics of cubic and hexagonal SrMnO3: Calorimetry and density functional theory simulations. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  75, s 214307-1- 214307-8 . doi: 10.1103/PhysRevB.75.214307
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2007). A new series of high hydrogen content hydrogen-storage materials - A theoretical prediction. Journal of Alloys and Compounds.  ISSN 0925-8388.  446, s 44- 47 . doi: 10.1016/j.jallcom.2006.12.058
• Karazhanov, Smagul; Ravindran, Ponniah; Grossner, Ulrike; Kjekshus, Arne; Fjellvåg, Helmer & Svensson, Bengt Gunnar (2006). Strong coulomb correlation effects in ZnO. Solid State Communications.  ISSN 0038-1098.  139, s 391- 396
• Karazhanov, Smagul; Ravindran, Ponniah; Kjekshus, Arne; Fjellvåg, Helmer; Grossner, Ulrike & Svensson, Bengt Gunnar (2006). Coulomb correlation effects in zinc monochalcogenides. Journal of Applied Physics.  ISSN 0021-8979.  100
• Klaveness, Arne; Vajeeston, Ponniah; Ravindran, Ponniah; Fjellvåg, Helmer; Li, Yanjun & Kjekshus, Arne (2006). Structural phase stability and bonding behavior of BAlH5 (B=Mg,Ba) from first-principles calculations. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  73
• Ravindran, Ponniah; Vajeeston, Ponniah; Vidya, R.; Fjellvåg, Helmer & Kjekshus, A (2006). Modeling of hydrogen storage materials by density-functional calculations. Journal of Power Sources.  ISSN 0378-7753.  159, s 88- 99
• Ravindran, Ponniah; Vidya, R.; Kjekshus, Arne; Fjellvåg, Helmer & Eriksson, O. (2006). Theoretical investigation of magnetoelectric behavior in BiFeO3. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  74
• Vajeeston, Ponniah; Ravindran, Ponniah; Hauback, BC; Fjellvåg, Helmer; Kjekshus, Arne; Furuseth, Sigrid Breien & Hanfland, M (2006). Structural stability and pressure-induced phase transitions in MgH2. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  73
• Vajeeston, Ponniah; Ravindran, Ponniah; Kjekshus, Arne & Fjellvåg, Helmer (2006). High hydrogen content complex hydrides: A density-functional study. Applied Physics Letters.  ISSN 0003-6951.  89
• Vidya, R.; Ravindran, Ponniah; Fjellvåg, Helmer & Kjekshus, Arne (2006). Spin- and charge-ordering in oxygen-vacancy-ordered mixed-valence Sr4Fe4O11. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  74
• Vidya, R.; Ravindran, Ponniah; Kjekshus, A & Fjellvåg, Helmer (2006). Density-functional calculations of the crystal structures and properties of CsCr3O8 and ACr(3)O(8) (A=In,Tl,Cu,Ag,Au). Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  73
• Vidya, R.; Ravindran, Ponniah; Kjekshus, Arne & Fjellvåg, Helmer (2006). Crystal and electronic structures of Cr3O8 and LiCr3O8: Probable cathode materials in Li batteries. Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  73
• Vidya, R.; Ravindran, Ponniah; Kjekshus, Arne & Fjellvåg, Helmer (2006). First-principles density-functional calculations on HCr3O8: An exercise to better understand the ACr(3)O(8) (A = alkali metal) family. Journal of Electroceramics.  ISSN 1385-3449.  17, s 15- 20 . doi: 10.1007/s10832-006-9929-6
• Stølen, Svein; Mohn, Chris Erik; Ravindran, Ponniah & Allan, Neil (2005). The topography of the potential energy hypersurface and criteria for fast-ion-conduction in perovskite-related A2B2O5-oxides. Journal of Physical Chemistry B.  ISSN 1520-6106.  109, s 12362- 12365

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• Lokanath, Patra & Ponniah, Ravindran (2017). First-principles prediction of coexistence of magnetism and ferroelectricity in BiFeWO6.
• Lokanath, Patra & Ponniah, Ravindran (2017). Prediction of Magnetoelectric behavior in Bi2MnTiO6. AIP Conference Proceedings.  ISSN 0094-243X.  1832, s 130053
• M R, Ashwin Kishore & Ponniah, Ravindran (2017). Effect of H Impurity on the Photocatalytic Activity of C2N Monolayer.
• Lokanath, Patra & Ponniah, Ravindran (2015). Electronic and magnetic structures of hole doped trilayer La4Ni3O8 from first principles.
• M R, Ashwin Kishore & Ponniah, Ravindran (2015). Electronic Structure and Magnetic Properties of Mn5O8.
• Vajeeston, Ponniah; Ravindran, Ponniah & Fjellvåg, Helmer (2012). Reply to "A comment on 'Prediction of crystal structure, lattice dynamical, and mechanical properties of CaB2H2' by Vajeeston et al., Int J Hydrogen Energy, 36 (2011) 10149-10158" Discussion. International Journal of Hydrogen Energy.  ISSN 0360-3199.  37(3), s 2711- 2712 . doi: 10.1016/j.ijhydene.2011.10.097
• Kalantzopoulos, Georgios N.; Frommen, Christoph; Sørby, Magnus Helgerud; Ravindran, Ponniah; Fjellvåg, Helmer & Hauback, Bjørn (2011). Crystal Structure and Thermal Properties of Novel Mixed-Metal and Anion-Substituted Borohydrides.
• Larsen, Kjersti Beate; Fjellvåg, Helmer; Bakken, Vebjørn; Ponniah, Ravindran & Helgaker, Trygve (2011). DFT-modellering av elektroniske og optiske egenskaper i CPO-27-Zn.
• Ravindran, Ponniah; Vidya, R.; Fjellvåg, Helmer & Kjekshus, Arne (2008). Reply to "Comment on 'Spin- and charge-ordering in oxygen-vacancy-ordered mixed-valence Sr4Fe4O11' ". Physical Review B. Condensed Matter and Materials Physics.  ISSN 1098-0121.  77 . doi: 10.1103/PhysRevB.77.136402 Vis sammendrag

  Recently, using d.-functional theor. calcns., we have reported (2006) that formal Fe3+ ions reside at the square-pyramidal site and Fe4+ ions in the octahedral site in Sr4Fe4O11. Based on the interpretation of exptl. structural and Mossbauer data from the literature, Adler concludes that our previous first-principles results disagree with expts. on the assignment of oxidn. states to Fe in the square-pyramidal and octahedral environments in Sr4Fe4O11. From a crit. examn. of the structure data for Sr4Fe4O11 and related oxides with Fe in different oxidn. states and theor. simulated Mossbauer parameters (hyperfine field, isomer shift, and quadrupole splitting), here we show that information on charges residing on the different constituents cannot be directly derived either from exptl. structure or Mossbauer data. From addnl. analyses of the chem. bonding on the basis of charge d., charge transfer, electron localization function, crystal orbital Hamilton population, Born effective charge, and partial d. of states, we substantiate our previous assignment of formal Fe3+ and Fe4+ to the square-pyramidal and octahedral sites, resp., in Sr4Fe4O11.

• Ravindran, Ponniah; Offernes, Laila & Kjekshus, Arne (2007). Comment on "Optical and magneto-optical properties of AuMnSn" [Appl. Phys. Lett. 88, 121909 (2006)]. Applied Physics Letters.  ISSN 0003-6951.  91 . doi: 10.1063/1.2804560
• Karazhanov, Smagul; Ravindran, Ponniah; Ulyashin, Alexander; Vajeeston, Ponniah & Finstad, Terje (2006). Electronic Structure and Optical Properties of Indium Tin Oxide.

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