Crystallography of selected high pressure elemental solids

Recent advancements in instrumentations using high brilliance X-ray from 3(rd) generation synchrotrons have greatly improved the quality of powder diffraction data obtained from a diamond anvil cell. In conjunction with new and better structural refinement techniques, as a result many new structures of solids at high pressures have been discovered and characterized. These structures are often novel and sometimes not seen in any solids under ambient conditions. These observations challenge the conventional concept of chemical bonding for solids and provide a fertile ground for the investigation of new physical phenomena in materials under high pressure. In this article, high pressure structures and transformations of selected elemental solids is illustrated and discussed. The purpose is to develop a conceptual model for the description of the structures and the understanding of the nature of chemical bonding.