The high-pressure phase of zincite.

Synchrotron-radiation X-ray diffraction studies of ZnO have been performed with special emphasis on the rock-salt-type high-pressure phase. The wurtzite (B4) to rock salt (B1) phase transformation is accompanied by a volume collapse of 18%, which is a very large effect. The lattice constant of the B1 phase at ambient pressure is a(0) = 4.280 (4) A, and the bulk modulus is B(0) = 170 (10) GPa. Comparisons are made with a recently published theoretical equation of state obtained from ab initio perturbed-ion calculations.