Abstract The structures of the silica polymorphs α-quartz and stishovite have been geometry optimized at highly simulated isotropic pressure within the framework of Density Functional Theory. The atoms of the high-pressure polymorph stishovite are virtually incompressible with the bonded radii for Si and O atoms decreasing by only 0.04 and 0.08 Å, respectively, at 100 GPa. In compensating for the increase in the effective interatomic potential associated with the compression of the Si-O bonded interactions, the electron density at the bond critical point between the bonded pair increases from 0.69 to 0.89 e/ Å3. The bonded radii of the Si and O atoms for α-quartz decrease by 0.006 and 0.008 Å, respectively, between 1 bar and 26.4 GPa. The impact of simulated, isotropic pressure on the bonded radii of the atoms for three perovskites YAlO3, LaAlO3, and CaSnO3 was also examined at high pressure. For the YAlO3 perovskite, the bonded radii for Y and Al decrease by 0.06 and 0.05 Å, respectively, at 80 GPa, while the electron density between the bonded atoms increases by 0.12 and 0.15 e/Å3, on average. The calculations also show that the coordination number of the Y atom increases from 9 to 10 while the coordination number of the O1 atom increases concomitantly in the structure from 5 to 6 at 20 GPa. Hence pressure not only promotes an increase in the coordination number of the metal atoms but also a necessary concomitant increase in the coordination number of the O atoms. The bonded radii, determined at a lower pressure between 0.0 and 15 GPa for LaAlO3 and CaSnO3, decrease a smaller amount with the radii for the La and Ca atoms decreasing by 0.03 and 0.04 Å, respectively, while the radii for the smaller Al and Sn atoms decrease by 0.01 and 0.02 Å, respectively. In general, O atoms are more compressible than the metal atoms, but overall the calculations demonstrate that the bonded radii for the atoms in crystals are virtually incompressible when subjected to high pressure. The reason that the bonded radii change little when subjected to high pressure is ascribed to the changes in the effective interatomic potentials that result in increased repulsion when the atoms are squeezed together.

中文翻译：

---

原子在高压下的不可压缩性

摘要 在密度泛函理论的框架内，在高度模拟的各向同性压力下对二氧化硅多晶型 α-石英和 stishovite 的结构进行了几何优化。高压多晶型 stishovite 的原子实际上是不可压缩的，Si 和 O 原子的键合半径在 100 GPa 下分别仅减少 0.04 和 0.08 Å。为了补偿与 Si-O 键合相互作用压缩相关的有效原子间势的增加，键合对之间键临界点处的电子密度从 0.69 增加到 0.89 e/ Å3。在 1 bar 和 26.4 GPa 之间，α-石英的 Si 和 O 原子的键合半径分别减少了 0.006 和 0.008 Å。模拟的各向同性压力对三种钙钛矿 YAlO3、LaAlO3、CaSnO3 也在高压下进行了检测。对于 YAlO3 钙钛矿，在 80 GPa 下，Y 和 Al 的键合半径分别减少 0.06 和 0.05 Å，而键合原子之间的电子密度平均增加 0.12 和 0.15 e/Å3。计算还表明，在 20 GPa 下，Y 原子的配位数从 9 增加到 10，而 O1 原子的配位数在结构中从 5 增加到 6。因此，压力不仅促进了金属原子配位数的增加，而且还促进了 O 原子配位数的必要伴随增加。LaAlO3 和 CaSnO3 在 0.0 到 15 GPa 之间的较低压力下确定的键合半径随着 La 和 Ca 原子的半径分别减少 0.03 和 0.04 Å 而减少了较小的量，而较小的 Al 和 Sn 原子的半径分别减少 0.01 和 0.02 Å。一般来说，O 原子比金属原子更容易压缩，但总体而言，计算表明晶体中原子的键合半径在承受高压时实际上是不可压缩的。当受到高压时，键合半径几乎没有变化的原因是有效原子间势的变化导致当原子被挤压在一起时排斥力增加。