The general availability of third generation synchrotron sources has ushered in a new era of high pressure research. The crystal structure of materials under compression can now be determined by X-ray diffraction using powder samples and, more recently, from multi-nano single crystal diffraction. Concurrently, these experimental advancements are accompanied by a rapid increase in computational capacity and capability, enabling the application of sophisticated quantum calculations to explore a variety of material properties. One of the early surprises is the finding that simple metallic elements do not conform to the general expectation of adopting 3D close-pack structures at high pressure. Instead, many novel open structures have been identified with no known analogues at ambient pressure. The occurrence of these structural types appears to be random with no rules governing their formation. The adoption of an open structure at high pressure suggested the presence of directional bonds. Therefore, a localized atomic hybrid orbital description of the chemical bonding may be appropriate. Here, the theoretical foundation and experimental evidence supporting this approach to the elucidation of the high pressure crystal structures of group I and II elements and polyhydrides are reviewed. It is desirable and advantageous to extend and apply established chemical principles to the study of the chemistry and chemical bonding of materials at high pressure.

中文翻译：

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高压晶体结构和性质的化学视角

第三代同步加速器源的普遍可用性开启了高压研究的新时代。现在可以通过使用粉末样品的 X 射线衍射以及最近的多纳米单晶衍射来确定压缩材料的晶体结构。同时，这些实验进步伴随着计算能力和能力的快速增长，使得复杂的量子计算能够应用来探索各种材料特性。早期的惊喜之一是发现简单的金属元素不符合在高压下采用 3D 密堆积结构的普遍预期。取而代之的是，在环境压力下，许多新颖的开放结构已被确定，而没有已知的类似物。这些结构类型的出现似乎是随机的，没有规则控制它们的形成。在高压下采用开放结构表明存在定向键。因此，化学键的局部原子杂化轨道描述可能是合适的。在这里，回顾了支持这种方法来阐明 I 族和 II 族元素和多氢化物的高压晶体结构的理论基础和实验证据。将已建立的化学原理扩展和应用到高压下材料的化学和化学键合研究是可取的和有利的。化学键的局部原子杂化轨道描述可能是合适的。在这里，回顾了支持这种方法来阐明 I 族和 II 族元素和多氢化物的高压晶体结构的理论基础和实验证据。将已建立的化学原理扩展和应用到高压下材料的化学和化学键合研究是可取的和有利的。化学键的局部原子杂化轨道描述可能是合适的。在这里，回顾了支持这种方法来阐明 I 族和 II 族元素和多氢化物的高压晶体结构的理论基础和实验证据。将已建立的化学原理扩展和应用到高压下材料的化学和化学键合研究是可取的和有利的。