Equation of state of lead from high-pressure neutron diffraction up to 8.9 GPa and its implication for the NaCl pressure scale
From high-resolution neutron-diffraction experiments we present equation-of-state (EOS) data of elemental lead as functions of both temperature (80-298 K) and applied pressure (up to 8.9 GPa), with the pressure values derived from the NaCl pressure gauge. Based on Brown's 1999 NaCl EOS we find the bulk modulus of lead of B-0 = 41.2(2) GPa at 298 K to increase by 14% to B-0 = 47.0(5) GPa by 80 K. The ambient temperature value coincides within 0.35 GPa (1.7%) of the value determined from published ultrasonic data. The good agreement between the neutron and ultrasonic data deteriorates if pressure values are derived from Decker's 1971 scale. Our results hence lend significant support to Brown's revised NaCl pressure standard. Furthermore, the experimental results are compared with T = 0 K first-principles calculations.