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 melting under shock compression. The comparison between the measured sound velocity data sets above ∼225 GPa and calculated values yields γ0∼2.0 and the empirical expression γρ=γ0ρ0 is basically tenable. Additionally, shock temperatures along the principal Hugoniot of vanadium were also determined from interfacial radiation intensities according to Grover's ideal interface model. Thus the temperature at this solid-liquid phase transition was constrained to be round about 7800(±800) K on the basis of the measured Hugoniot temperatures, melting temperatures, and high-pressure sound velocity variations with pressure. (author)