Compressive behaviors of bcc bismuth up to 55 GPa



Bismuth was compressed hydrostatically and nonhydrostatically up to 55 GPa in a diamond anvil cell. The strength of bcc bismuth was determined by the radial X-ray diffraction (RXRD) technique: Y = −0.20(5) + 0.009(1)P, which is much smaller than that of normal pressure-transmitting media (PTM), such as NaCl, Ar, and He. Different PTM [silicone oil (SO), Ar, and He] were used to determine the hydrostatical equation of state of bcc bismuth. The determined results are consistent with each other when different PTM were used, even when no PTM was used. The typical bulk modulus and its pressure derivation of bcc bismuth are 42.7(6) GPa and 5.3(1), respectively. The differential strain introduced by nonhydrostatic stress was derived from Hooke's law and lattice strain theory (LST). The differential strain in bismuth is very small even when no PTM was used. Because of the simple, stable structure and small strength, bcc bismuth is an ideal candidate for an internal pressure standard.