HIGH-PRESSURE MELTING TEMPERATURES OF URANIUM - LASER-HEATING EXPERIMENTS AND THEORETICAL CALCULATIONS

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 mum at the center of laser-heating spot using reflecting optics, and the melting was visually observed as the material flows forming a micr ochannel and/or by a shape change in the edge of the sample. Theoretic ally, the melting curve has also been calculated to 100 GPa via gamma( bcc) solid and liquid free energies derived from generalized pseudopot ential theory. The calculated melting temperatures agree well with the experimental measurements. It is also found that the theoretical melt ing curve obeys a Lindemann scaling law for solid densities up to abou t 25.5 g/cm-3, corresponding to 100 GPa in pressure.