B1-B2 Transition in Calcium Oxide from Shock-Wave and Diamond-Cell Experiments
- 16 November 1979
- journal article
- other
- Published by American Association for the Advancement of Science (AAAS) in Science
- Vol. 206 (4420) , 829-830
- https://doi.org/10.1126/science.206.4420.829
Abstract
Volume and structural data obtained by shock-wave and diamond-cell techniques demonstrate that calcium oxide transforms from the B1 (sodium chloride type) to the B2 (cesium chloride type) structure at 60 to 70 gigapascals (0.6 to 0.7 megabar) with a volume decrease of 11 percent. The agreement between the shockwave and diamond-cell results independently confirms the ruby-fluorescence pressure scale to about 65 gigapascals. The shock-wave data agree closely with ultrasonic measurements on the B1 phase and also agree satisfactorily with equations of state derived from ab initio calculations. The discovery of this B1-B2 transition is significant in that it allows considerable enrichment of calcium components in the earth's lower mantle, which is consistent with inhomogeneous accretion theories.Keywords
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