ABSTRACT

The mechanical and anisotropic elastic properties of Bi₁₂SiO₂₀ (BSO) were investigated using density functional theory (DFT) calculations and nanoindentation. The calculated and experimentally observed XRD patterns of the compound were reported and the crystal structure of the BSO was determined to be cubic with the lattice constant of a = 1.025 nm. The second-order elastic constants and related polycrystalline elastic moduli (e.g. shear modulus, Young’s modulus, Poisson’s ratio, linear compressibility and hardness) were calculated. The calculated elastic constants indicated that BSO is mechanically stable and exhibits anisotropic characteristics. Moreover, the directional dependencies of sound wave velocities were investigated in three dimensions. Pressure-dependent bulk modulus was plotted at temperatures between 0 and 800 K. Hardness and Young’s modulus were also determined by performing nanoindentation experiments on (222) and (631) planes of the BSO single crystal. The analyses of the experimental nanoindentation data resulted in hardness and Young’s modulus values of 7.2 and 97.0 GPa, respectively. The results of DFT and nanoindentation were discussed throughout the paper. The results of the present paper would provide valuable information on the mechanical behaviours of the BSO for the optoelectronic device applications.

摘要

使用密度泛函理论 (DFT) 计算和纳米压痕研究了 Bi ₁₂ SiO ₂₀ (BSO)的机械和各向异性弹性性能。所述化合物的计算的和实验上观察到X射线衍射图案被报告并测定BSO的晶体结构是立方与的晶格常数一 = 1.025 纳米。计算了二阶弹性常数和相关的多晶弹性模量（例如剪切模量、杨氏模量、泊松比、线性压缩率和硬度）。计算出的弹性常数表明 BSO 是机械稳定的并表现出各向异性特性。此外，在三个维度上研究了声波速度的方向依赖性。在 0 到 800 K 之间的温度下绘制与压力相关的体积模量。硬度和杨氏模量也通过在 BSO 单晶的 (222) 和 (631) 平面上进行纳米压痕实验来确定。对实验纳米压痕数据的分析导致硬度和杨氏模量值分别为 7.2 和 97.0 GPa。通篇讨论了 DFT 和纳米压痕的结果。