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Author: search.filters.author.Limpijumnong, SukitSubject: search.filters.subject.First principles

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    First Principles Calculations of Structural and Elastic Properties of Perovskite Crystals: The Case of SrTiO3
    (2016-06-01)
    Pandech, Narasak
    ;
    Sarasamak, Kanoknan
    ;
    Limpijumnong, Sukit
    The structural and elastic properties of perovskite crystals can be independently calculated by using first principles calculations without bias. The detailed calculation of cubic perovskite (Pm3m) crystal by first-principles calculations both LDA and GGA approaches was shown, using SrTiO<inf>3</inf> as an illustration case. The equilibrium volumes and bulk modulus of SrTiO<inf>3</inf> were evaluated by fitting to Birch-Murnaghan equation of states. The C<inf>11</inf>, C<inf>12</inf>, and C<inf>44</inf> elastic constants were obtained from a polynomial fit to the calculated energy-strain relations. For SrTiO<inf>3</inf>, the calculated lattice constants, bulk modulus, and all three elastic constants by both LDA and GGA calculations are in good agreement with experimental values. Because LDA gives a slightly smaller lattice constant compared to that obtained from GGA, the bulk modulus and all three elastic constants obtained from LDA are slightly larger than those values obtained from GGA. The calculation steps illustrated here can be used as a guideline to study elastic properties of other novel materials.
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    Sound velocities and elastic properties of PbTiO3 and PbZrO 3 under pressure: First principles study
    (2013-05-01)
    Pandech, Narasak
    ;
    Sarasamak, Kanoknan
    ;
    Limpijumnong, Sukit
    The elastic constants and sound velocities as a function of pressure for perovskite materials PbTiO<inf>3</inf> (PTO) and PbZrO<inf>3</inf> (PZO) were investigated by first principles calculations. Under ambient pressure, the calculated structural parameters were calculated and found to be in good agreement with known values. To study properties under pressure, PTO and PZO were calculated at several reduced volumes, each of which corresponds to the system under pressure. The C<inf>11</inf>, C<inf>12</inf> and C<inf>44</inf> elastic constants are all found to increase with pressure for the pressure range studied. Because the sound velocities are directly derived from the elastic constants, the relationships between the sound velocities and pressure also follow similar trends. The longitudinal modes are all larger than those of the transverse modes. © 2012 Elsevier Ltd and Techna Group S.r.l.