Using density-functional theory calculations, we determined the pressure domain of stability of beryllium metasilicate, BeSiO₃, an elusive compound for which no stable polymorph is known until now. We found that BeSiO₃ is stable at pressures above 9 GPa, a condition that makes it accessible with a large-volume press. After considering the cubic, orthorhombic, and hexagonal perovskite structures and the Ilmenite structure, known from related compounds, we propose that the most stable structure among them is the orthorhombic perovskite structure described by space group Pnma. The unit-cell parameters of this structure are a = 4.966 Å, b = 7.160 Å, and c = 4.374 Å. We also determined the frequencies of Raman and infrared phonons, the elastic constants and modulus, and the electronic band structure for the orthorhombic perovskite structure. Finally, the pressure dependence of unit-cell parameters was calculated. Compression was found to be slightly anisotropic, with the axial compressibilities decreasing following the sequence κ_b > κ_c > κ_a. In addition, we found that BeSiO₃ is quite incompressible with a bulk modulus of 242 GPa, which makes it one of the less compressible silicates. To understand, such a large bulk modulus, both the quantum theory of atoms in molecules and the electron localization function decomposition were utilized to analyze the bonding and to relate it to the mechanical properties.

中文翻译：

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BeSiO3 高压稳定域的测定及其晶体结构和性能的表征


使用密度泛函理论计算，我们确定了偏硅酸铍 BeSiO 3 的压力稳定性域，BeSiO₃ 是一种难以捉摸的化合物，到目前为止还没有稳定的多晶型物。我们发现 BeSiO₃ 在高于 9 GPa 的压力下是稳定的，这一条件使其可以通过大容量压力机获得。在考虑了从相关化合物中得知的立方体、斜方和六方钙钛矿结构以及钛铁矿结构后，我们提出其中最稳定的结构是空间群 Pnma 描述的斜方钙钛矿结构。该结构的晶胞参数为 a = 4.966 Å、b = 7.160 Å 和 c = 4.374 Å。我们还确定了拉曼和红外声子的频率、弹性常数和模量，以及正交钙钛矿结构的电子能带结构。最后，计算了晶胞参数的压力依赖性。发现压缩是轻微各向异性的，轴向压缩率沿着 κ_b > κ_c > κ_a 序列降低。此外，我们发现 BeSiO₃ 非常不易压缩，体积模量为 242 GPa，这使其成为不易压缩的硅酸盐之一。为了理解如此大的体积模量，分子中原子的量子理论和电子局域函数分解都被用来分析键合并将其与机械性质联系起来。