The B1/B2 Transition in CaO from Shock-Wave and Diamond-Cell Experiments

There is considerable interest in B1/B2 transitions in theoretical studies of oxide structures (Tosi and Arai, 1966; Cohen and Gordon, 1976; Demarest et al., 1977), and interest also in their possible occurrence in the earth's lower mantle. Volume and crystal-structure data obtained by both dynamic shockwave and static diamond-cell techniques indicate that CaO transforms from the B1 (NaCl-type) to the B2 (CsCl-type) structure at 0.6-0.7 Mbar with a volume decrease of 11 %.