First-Principles Calculations for High-Pressure Synthesis of Novel Materials

Abstract

Basic approaches of first-principles calculations for high-pressure synthesis of novel materials were discussed. Stabilities of materials under high-pressure conditions were often explained using enthalpies H, which are estimated with total energies in electronic structure calculations, volumes of materials and pressure. First-principles calculations reveal that the pressure dependence of enthalpies is mainly composed of that of the product of pressure and volumes rather than that of the total energies not only in hard materials but also in soft materials such as molecular crystals. Therefore, the volumes of materials play important roles for high-pressure phase transitions and chemical reactions under high-pressure conditions. Phase transitions during decompression process were also investigated using first-principles methods. Since the phase transitions are caused by mobile ions, configurations of immobile ions have the key to recovery of high-pressure phases.