High-pressure melting temperatures of uranium: Laser-heating experiments and theoretical calculations.

Abstract

The melting temperatures of uranium have been measured to 45 GPa with an inert Ar pressure medium in a diamond-anvil cell using a spatially resolved laser-heating system. The temperature was measured within 1.4 \ensuremath{\mu}m at the center of laser-heating spot using reflecting optics, and the melting was visually observed as the material flows forming a microchannel and/or by a shape change in the edge of the sample. Theoretically, the melting curve has also been calculated to 100 GPa via \ensuremath{\gamma}(bcc) solid and liquid free energies derived from generalized pseudopotential theory. The calculated melting temperatures agree well with the experimental measurements. It is also found that the theoretical melting curve obeys a Lindemann scaling law for solid densities up to about 25.5 g/${\mathrm{cm}}^{\mathrm{\ensuremath{-}}3}$, corresponding to 100 GPa in pressure.