Drastic Transformation of Tetrahedral Molecules at High Pressure

Abstract

Recent applications of the first-principles molecular dynamics method to the study of structural transformation of some tetrahedral molecules are reported. Contrary to the interpretation of shock-wave experiments, CH₄ was found to dissociate into a mixture of hydrocarbons below 100 GPa and separate into diamond and hydrogen only above 300 GPa. The fcc-phase of SnI₄ above 60 GPa was unambiguously shown to be a substitutional solid solution of Sn into fcc I. B₂H₆, in which BH₄ tetrahedra shares an edge, will undergo more extensive polymerization leaving fewer isolated hydrogen molecules.