Density functional theory for calculation of elastic properties of orthorhombic crystals:: Application to TiSi2
Density functional theory for calculation of elastic properties of orthorhombic crystals:: Application to TiSi2
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DOI：
10.1063/1.368733
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发表时间：
1998-11-01
影响因子：
3.2
通讯作者：
Eriksson, O
中科院分区：
文献类型：
--
作者：
Ravindran, P;Fast, L;Eriksson, O
本文介绍了一种从第一性原理计算正交晶体单晶弹性常数的理论公式。将这一方法应用于TiSi2，利用局域密度近似(LDA)和广义梯度近似(GGA)，采用全势线性松饼-锡轨道方法计算了TiSi2的弹性常数。计算值与最近的实验结果吻合较好。导出了用弹性常数计算单晶沿晶轴方向的体弹性系数的表达式。由此计算得到的线性体弹模值与实验值吻合较好。计算了理想多晶TiSi2的剪切模数、杨氏模数和泊松比，并与相应的实验值进行了比较。根据LDA和GGA计算得到的弹性常数，估算了单晶TiSi2的定向体弹性系数和杨氏弹性系数，并与实验结果进行了比较。由单晶弹性常数得到了剪切各向异性因子和线体弹性模中的各向异性。从格点和角动量分解态密度出发，结合电荷密度分析和弹性各向异性，分析了TiSi2中各组分之间的化学键性质。德拜温度是由单晶的剪切弹性波速和体弹性模量得到的平均弹性波速，以及单晶不同方向的弹性波速的积分得到的。当交换势和关联势采用广义梯度近似时，计算的弹性性质与实验值符合得很好。(C)1998年美国物理研究所。[S0021-8979(98)03821-3]。
A theoretical formalism to calculate the single crystal elastic constants for orthorhombic crystals from first principle calculations is described. This is applied for TiSi2 and we calculate the elastic constants using a full potential linear muffin-tin orbital method using the local density approximation (LDA) and generalized gradient approximation (GGA). The calculated values compare favorably with recent experimental results. An expression to calculate the bulk modulus along crystallographic axes of single crystals, using elastic constants, has been derived. From this the calculated linear bulk moduli are found to be in good agreement with the experiments. The shear modulus, Young's modulus, and Poisson's ratio for ideal polycrystalline TiSi2 are also calculated and compared with corresponding experimental values. The directional bulk modulus and the Young's modulus for single crystal TiSi2 are estimated from the elastic constants obtained from LDA as well as GGA calculations and are compared with the experimental results. The shear anisotropic factors and anisotropy in the linear bulk modulus are obtained from the single crystal elastic constants. From the site and angular momentum decomposed density of states combined with a charge density analysis and the elastic anisotropies, the chemical bonding nature between the constituents in TiSi2 is analyzed. The Debye temperature is calculated from the average elastic wave velocity obtained from shear and bulk modulus as well as the integration of elastic wave velocities in different directions of the single crystal. The calculated elastic properties are found to be in good agreement with experimental values when the generalized gradient approximation is used for the exchange and correlation potential. (C) 1998 American Institute of Physics. [S0021-8979(98)03821-3].