The structural, electronic, and elastic properties of tetragonal phase of SnTiO3 and PbTiO3 are investigated using first principle calculations. The unknown exchange-correlation functional is approximated with generalized gradient approximation (GGA) as implemented in pseudopotential plane wave approach. The convergence test of total energy with respect to energy cutoff and k-point sampling is preformed to ensure the accuracy of the calculations. The structural properties such as equilibrium lattice constant, equilibrium unit cell volume, bulk modulus, and its derivative are in reasonable agreement with the previous experimental and theoretical works. From elastic constants, mechanical parameters such as anisotropy factor A, shear modulus G, bulk modulus B, Young’s modulus E, and Poison’s ratio n are determined by using Voigt–Reuss–Hill average approximation. In addition, Debye temperature and longitudinal and transversal sound velocities are predicted from elastic constants. The electronic band structure and density of states of both compounds are obtained and compared with the available experimental as well as theoretical data. Born effective charge (BEC), phonon dispersion curve, and density of states are computed from functional perturbation theory (DFPT). Lastly, the spontaneous polarization is determined from the modern theory of polarization, and they are in agreement with the previous findings.

中文翻译：

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使用密度泛函理论研究 SnTiO3 和 PbTiO3 的结构、电子、晶格动态和弹性特性

使用第一性原理计算研究了 SnTiO3 和 PbTiO3 的四方相的结构、电子和弹性特性。未知的交换相关泛函近似于广义梯度近似 (GGA)，如在赝势平面波方法中实现的。针对能量截止和k点采样进行了总能量的收敛测试，以确保计算的准确性。平衡晶格常数、平衡晶胞体积、体积模量及其导数等结构特性与之前的实验和理论工作具有合理的一致性。从弹性常数、机械参数如各向异性因子 A、剪切模量 G、体积模量 B、杨氏模量 E，和 Poison 的比率 n 是通过使用 Voigt-Reuss-Hill 平均近似确定的。此外，德拜温度和纵向和横向声速是根据弹性常数预测的。获得了两种化合物的电子能带结构和态密度，并与可用的实验和理论数据进行了比较。出生有效电荷 (BEC)、声子色散曲线和状态密度是根据功能微扰理论 (DFPT) 计算的。最后，自发极化是由现代极化理论确定的，它们与先前的发现一致。获得了两种化合物的电子能带结构和态密度，并与可用的实验和理论数据进行了比较。出生有效电荷 (BEC)、声子色散曲线和状态密度是根据功能微扰理论 (DFPT) 计算的。最后，自发极化是由现代极化理论确定的，它们与先前的发现一致。获得了两种化合物的电子能带结构和态密度，并与可用的实验和理论数据进行了比较。出生有效电荷 (BEC)、声子色散曲线和状态密度是根据功能微扰理论 (DFPT) 计算的。最后，自发极化是由现代极化理论确定的，它们与先前的发现一致。