ダイヤモンドアンビル法を主体とするキューバ鉱相変化の観察

抄録

A diamond anvil cell was used to investigate the phase relations between low and high temperature phases of cubanite and also between high pressure polymorph and the above-stated phases. Initial slope of low-high temperature phase boundary is about 200°C/GPa, showing a good coincidence with the reported value. Compressions of both low and high temperature phases produce a high pressure modification isostructural with troilite. The conversion accompanies an increase in density of 23%. This compaction is induced by a change of coordination numbers of anions surrounding cations from 4 to 6. The dense phase reverts to high temperature phase but not to low temperature. No significant difference was seen in heat capacities of low and high temperature phases. This implies the structural resemblance between two phases. The change of enthalpy accompanied with the transformation between low and high temperature phases was mainly attributed to the order-disorder transitions of both magnetic and ionic configurations in the lattice.