Raman shift of stressed diamond anvils: Pressure calibration and culet geometry dependence

The pressure dependence of the Raman shift of diamond for highly stressed anvils at the diamond anvil sample interface has been measured for different culet shapes up to 180 GPa at ambient temperature. By using hydrogen samples, which constitute both a quasihydrostatic medium and a sensitive pressure sensor, some of the effects of culet and tip size have been determined. We propose that the divergent results in the literature can be partly ascribed to different anvil geometries. Experiments show increasing second order dependence of the diamond Raman shift with pressure for decreasing tip size. This is an important consideration when using the diamond anvils as a pressure sensor. (C) 2008 American Institute of Physics.