Experimental and theoretical high pressure study of beta-Cs2SO4

The high pressure behaviour of the room temperature modification of cesium sulfate, beta-Cs2SO4, has been studied by powder x-ray diffraction and by a b initio calculations based on density functional theory. The powder x-ray diffraction experiments were carried out using a diamond anvil cell mounted on an image plate system. The pressure dependence of the unit cell paramet ers was obtained for pressures up to 4.5 GPa. A fit with a 3(rd)-order Birc h-Murnaghan equation of state gave a bulk modulus, B-0 = 28.4(1.0) GPa, wit h a pressure derivative B-0' = 5.1(6). Quantum mechanical calculations have been used to study structural changes induced by compression.