THEORETICAL-STUDIES OF STRUCTURAL STABILITY AT HIGH-PRESSURE

Theoretical methods are indispensible for the study of matter at high pressure. In the last decade the development of accurate intermolecula r potentials and the methodologies in classical molecular dynamics (MD ) simulations have greatly facililated the applications of these metho ds to the study of structural phase transformamtions of solids at high pressures. More recently, it has been possible to incorporate quantum mechanical effects into MD calculations. This method eliminates a gre at deal of empiricism. These first principles calculations have not on ly reproduced the experimental results for phase transformations but a lso provided detailed mechanisms and in some cases predicted new struc tures that may be found at high pressures. The success of MD calculati ons is illustrated through a review of our studies of pressure-induced amorphization and phase transitions in SiO2 and TiO2, and the structu ral memory effect in several materials. Current applications using qua ntum molecular dynamics on ice are discussed.