新炭素系材料 フラーレンの結晶構造と相転移

Abstract

Fullerenes, a new allotrope of carbon, are hollow spherical all carbon molecules composed of six-membered and five-membered rings. Structural studies on C60 and C70 in the solid state at ambient and high pressure are reviewed Phase transitions under high pressures are associated with molecular rotation, orientational ordering, polymerization, and/or crushing of molecules. Tentative p-T phase diagrams for solid C60 and C70 are given. Under appropriate pressure and temperatures, fullerenes in the solid state transform to polymers and diamond. Bulk moduli at low pressures (≤1GPa) are also summarized.