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Author: search.filters.author.Sarasamak, KanoknanSubject: search.filters.subject.Elastic properties

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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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    First principles calculations of elastic properties under pressure in SiC
    (2010-04-20)
    Sarasamak, Kanoknan
    ;
    Limpijumnong, Sukit
    ;
    Lambrecht, Walter R.L.
    First principles density functional theory is employed to study the elastic constants and sound velocities in wurtzite-SiC under pressure. The focus is on the behavior of the elastic constants (C<inf>ij</inf>) and sound velocities (Cij/ρ) as a function of pressure. The pressure dependences of the transverse acoustic modes in sound velocities which correspond to the wurtzite to rocksalt phase transformation is analyzed. We found that the phase transformation from wurtzite to rocksalt structure relates to an orthorhombic strain with two components: (1) a traceless compression along the [0 0 0 1] axis which corresponds to the sound velocity C44/ρ and (2) a traceless compression along [011̄0] direction which corresponds to the sound velocity C66/ρ. © 2010 Elsevier B.V. All rights reserved.