Multiphase improved Steinberg-Guinan model for vanadium

Vanadium has been observed recently to transform from the body-centered cubic (bcc) crystal structure to a rhombohedral structure at high pressure (similar to 0.69 Mbar) [Y. Ding et al., Phys. Rev. Lett. 98, 085502 (2007)]. Recent theoretical work predicts a transformation to a second rhombohedral phase at 1.2 Mbar before transforming back to the bcc structure at 2.8 Mbar at absolute zero temperature [B. Lee et al., Phys. Rev. B 75, 180101 (R) (2007)]. Here we develop an analytic model for the shear modulus in these phases based on ab initio calculations of the single-crystal elastic moduli and a finite element based homogenization technique. The form of the shear modulus is suited to application in strength models such as in the Steinberg-Guinan form and other analogous continuum-level models. (C) 2008 American Institute of Physics. [DOI: 10.1063/1.3013429]