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Author: search.filters.author.Phacheerak, KanoknanSubject: search.filters.subject.First-principles

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    Pressure Dependence of Structural and Elastic Properties of Na2O: First-Principles Calculations
    (2022-01-01)
    Phacheerak, Kanoknan
    ;
    Thanomngam, Pitiporn
    The effect of high pressures, up to 40 GPa, on the structural and elastic properties of sodium oxide in cubic structure (c-Na<inf>2</inf>O) were investigated by first-principles calculations. The generalized gradient approximation (GGA) with the Perdew-Burke-Ernzerhof (PBE) functional was employed in the calculations. The calculated structural and elastic properties at zero pressure are consistent with the available results. The pressure dependence of structural and elastic properties was presented and discussed in detail. Under pressure, the elastic constants satisfy the Born criteria, indicating that c-Na<inf>2</inf>O is mechanically stable. Moreover, other elastic properties such as bulk modulus (B), shear modulus (G), and Young's modulus (E) under pressures were analyzed. Furthermore, the B/G values tend to increase with the increasing pressure, which means that pressure can improve the ductility of c-Na<inf>2</inf>O.
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    Elastic and mechanical properties of hydroxyapatite under pressure: A first-principles investigation
    (2020-09-01)
    Sailuam, Wutthigrai
    ;
    Phacheerak, Kanoknan
    ;
    Atipong bootchanont
    ;
    Fongkaew, Ittipon
    ;
    Limpijumnong, Sukit
    The structural, elastic, and mechanical properties of hydroxyapatite (HAp) were investigated by generalized gradient approximation (GGA) in the functional form by Perdew, Bruke, and Ernzerhof (PBE) exchange-correlation functional using density-functional theory. Our calculated equilibrium lattice parameters at ambient pressure are in good agreement with the experimental and previous theoretical results. The details of the structural, mechanical, and electrical properties such as elastic constants, bulk modulus B, shear modulus G, Young's modulus E, Poisson's ratioν, Cauchy pressure, shear anisotropic factor A, and total density of states under pressure ranging 0 GPa to 10 GPa are studied. The lattice parameters a and c are found to be decreased with increasing pressure. Moreover, the lattice parameter a is more sensitive to external pressure than c. The calculated elastic constants of hexagonal HAp increase with increasing pressure. The elastic constants C<inf>11</inf> and C<inf>33,</inf> which represent the elasticity in length are larger than the elasticity in shape, which represent by the elastic constants C<inf>12</inf>, C<inf>13</inf>, C<inf>44</inf>, and C<inf>66</inf>. The deformation resistances along the axial direction are stronger than the deformation resistances in shape. The calculated B/G, Poisson's ratio ν, and Cauchy pressure show that the hexagonal HAp behaves as a ductility material at ambient pressure and has more ductile under pressure. While the calculated shear anisotropic factor A indicate that the HAp shows elastic anisotropy under pressure. Moreover, calculated total density of states (DOS) show that HAp becomes more insulator property with increasing pressure.
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    First-principles investigations of structural and elastic properties of LiGaO2 under pressure
    (2019-09-01)
    Sailuam, Wutthigrai
    ;
    Busayaporn, Wutthikrai
    ;
    Limpijumnong, Sukit
    ;
    Phacheerak, Kanoknan
    The structural and elastic properties of the LiGaO<inf>2</inf> with an orthorhombic-type structure (Pna2<inf>1</inf>-LGO) under pressure were investigated using first-principles calculations. The calculated structural parameters and elastic constants show a good agreement with the experimental and other theoretical values. The structural parameters and elastic constants of Pna2<inf>1</inf>-LGO under various pressures are calculated. All structural parameters are found to be decreased with pressure. The elastic constants are found to increase with pressure, except for C<inf>44</inf> and C<inf>55</inf>. It was also found that the elastic constants C<inf>11</inf>, C<inf>22</inf>, and C<inf>33</inf> which represent the elasticity in length are always larger than the elastic constants C<inf>12</inf>, C<inf>13</inf>, C<inf>23</inf>, C<inf>44</inf>, C<inf>55</inf>, and C<inf>66</inf> which represent the elasticity in shape at the same pressure. The details of pressure dependences of the structural and elastic constants are also presented and discussed.