Ultrasonic interferometry and X-ray measurements on MgO in a new diamond anvil cell

The compressional sound wave velocity, nu(p), of synthetic MgO in the (100) direction and the unit-cell parameter have been measured up to a maximum p ressure of 6.1 GPa using a new type of diamond-anvil cell. The main feature of the cell is the transverse access of the X-ray beam into the sample cha mber. This allows us to undertake single crystal X-ray measurements while t he ultrasonic attachment is mounted on the diamond-anvil cell. The sound ve locity and the elastic parameter c(11) have been determined from these meas urements; the variation with pressure can be described by partial derivativ e c(11)/partial derivative p = 9.35(13), in good agreement with previous st udies.