Institute for Shock Physics and Department of Chemistry, Washington State University, Pullman, Washington 99164, USA.
Nat Chem. 2010 Sep;2(9):784-8. doi: 10.1038/nchem.724. Epub 2010 Jul 4.
The application of pressure, internal or external, transforms molecular solids into extended solids with more itinerant electrons to soften repulsive interatomic interactions in a tight space. Examples include insulator-to-metal transitions in O(2), Xe and I(2), as well as molecular-to-non-molecular transitions in CO(2) and N(2). Here, we present new discoveries of novel two- and three-dimensional extended non-molecular phases of solid XeF(2) and their metallization. At approximately 50 GPa, the transparent linear insulating XeF(2) transforms into a reddish two-dimensional graphite-like hexagonal layered structure of semiconducting XeF(4). Above 70 GPa, it further transforms into a black three-dimensional fluorite-like structure of the first observed metallic XeF(8) polyhedron. These simultaneously occurring molecular-to-non-molecular and insulator-to-metal transitions of XeF(2) arise from the pressure-induced delocalization of non-bonded lone-pair electrons to sp(3)d(2) hybridization in two-dimensional XeF(4) and to p(3)d(5) in three-dimensional XeF(8) through the chemical bonding of all eight valence electrons in Xe and, thereby, fulfilling the octet rule at high pressures.
施加压力（无论是内压还是外压）会将分子固体转变为具有更多巡游电子的扩展固体，从而软化紧密空间中原子间的排斥相互作用。例如，O(2)、Xe 和 I(2)中的绝缘体-金属转变，以及 CO(2)和 N(2)中的分子-非分子转变。在这里，我们介绍了固态 XeF(2)的新型二维和三维扩展非分子相及其金属化的新发现。在大约 50 GPa 时，透明线性绝缘的 XeF(2)转变为具有半导体性质的 XeF(4)的二维石墨状六方层状结构。在 70 GPa 以上，它进一步转变为首次观察到的金属 XeF(8)多面体的黑色三维萤石状结构。这些同时发生的 XeF(2)分子-非分子和绝缘体-金属转变源于压力诱导的非键孤对电子从二维 XeF(4)中的 sp(3)d(2)杂化到三维 XeF(8)中的 p(3)d(5)的离域化，以及 Xe 中所有八个价电子的化学成键，从而在高压下满足八隅体规则。
