High-pressure structural study of diopside

High-pressure structural studies performed on diopside at five pressures between I atm and 53 kbar show that the three polyhedra that comprise the structure, M(l), M(2), and Si, de­ crease irregularly in size. The polyhedral volumes of M(l) and M(2) both decrease approxi­ mately 5%, whereas that of Si decreases only 1%. Comparison of high-pressure structural changes of diopside and fassaite (another clinopyroxen e) shows substantial differences, with diopside showing less tetrahedral and M(l) compression and more silicate-chain kinking.