PRESSURE CALIBRATION ABOVE 100 KBAR BASED ON THE NaCl INTERNAL STANDARD

Abstract Transformation pressures of seven materials – Ba, Pb, ZnSe, ZnS, GaAs, and GaP–were studied, employing NaCl as the internal pressure standard. A cubic-anvil-type, high-pressure electrical-resistance apparatus was used in connection with an X-ray diffraction system. Based on Decker's equation of state for NaCl, transition pressures (in units of kbar) are: Transformation Pressure, kbar Material Increasing Pressure Cycle Decreasing Pressure Cycle Ba 126 112 Pb 142 111 Si 133 - ZnSe 139 105 ZnS 162 105 GaAs 193 107 GaP >233 - Present results are approximately 7% higher than those based on the ruby scale. The relation between present results and the results based on the new Drickamer scale is complicated. The effect of nonhydrostatic component of pressure is discussed.