PUTTING PRESSURE ON CRYSTALS: CHARLES PREWITT’S CONTINUING IMPACT

Investigations of the effects of pressure on the structure of minerals and related materials remain at the forefront of earth and planetary science. Through his own work and the research he has inspired in others, Charles Prewitt continues to lead this field. Several aspects comprise his approach: 1) the ansatz that understanding the origin of the physical properties of materials must start with detailed information about arrangement of their constituent atoms, 2) the role of elegant empiricism in the development of predictive models of structure and behavior based on real minerals and analog systems, 3) a consideration of electronic properties in controlling structure, 4) the uptake of volatiles and light elements in high-pressure phases, and perhaps most important 5) the continued development of new techniques, especially synchrotron radiation methods. These diverse themes are clearly evident in on-going work throughout the field of high-pressure mineralogy and crystallography, including the following recent studies from our laboratory. Recent experiments reveal new classes of framework oxide structures. Pressure-induced high-spin/low-spin transitions are now documented in dense mantle minerals using synchrotron high resolution emission spectroscopy techniques. New findings continue to be made in the high-pressure behavior of dense hydrous phases and the uptake of other volatiles. High-pressure structural studies of the end-members of these simple molecular systems (e.g., oxygen, nitrogen, hydrogen) give new insight into their atomic volumes at high pressure and hence thermochemical properties in planetary materials. Finally, entirely new classes of experiments are coming on line at new third generation high-energy synchrotron facilities and in the near future at the new generation of neutron sources.