Sound velocity variations and melting of vanadium under shock compression

The sound velocities of vanadium at shock pressure ranging from 154 to 250 GPa were determined using transparent-window optical analyser techniques. A discontinuity in sound velocities at about 225 GPa may mark the partial me lting under shock compression. The comparison between the measured sound ve locity data sets above similar to 225 GPa and calculated values yields gamm a (0) approximate to 2.0 and the empirical expression gamma rho = gamma (0) rho (0) is basically tenable. Additionally, shock temperatures along the pr incipal Hugoniot of vanadium were also determined from interfacial radiatio n intensities according to Grover's ideal interface model. Thus the tempera ture at this solid-liquid phase transition was constrained to be round abou t 7800(+/- 800) K on the basis of the measured Hugoniot temperatures, melti ng temperatures, and high-pressure sound velocity variations with pressure.