Survey of High-Pressure Effects in Solids.
Final rept. 21 May-30 Sep 79,
PACIFIC-SIERRA RESEARCH CORP SANTA MONICA CA
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The density-functional formalism is used as the framework within which to assess previous calculations and to suggest new avenues of research. As a result of the study, we judge that significant results should be obtained from theoretical high-pressure-physics investigations at one of three levels of sophistication the Gordon-Kim-Boyer scheme with our suggested modifications use of the exchange-correlation potential in the local-density approximation in such an accurate band-structure calculation as the augmented-plane-wave, Korringa-Kohn-Rostoker, or linear-combination-of-muffin-tin-orbital methods or a complete calculation of the electron dynamics in the local-density approximation, which would also be useful in calculating the phonon spectrum. This approach should yield good results for the equation of state, which is the required basis for studies of dynamic and nonlinear effects, structural transitions in insulators and semiconductors possibly providing a microscopic understanding of the successful ionicity scale of Phillips, simple insulator-metal transitions, polymorphic transitions in metals, and mixed-valence salt transitions. The state of the art in experimental and theoretical high-pressure physics research is surveyed in the context of recent studies on iodine, xenon, and cesium. Ultrahigh-pressure methods now under development are also reviewed. Author