Melting Behaviour of Mo by Shock Wave Experiment

In order to clarify the apparent discrepancy in determinations of melting temperature T_m of Mo between diamond-anvil cell (DAC) measurements from 0 to about 100GPa and shock wave (SW) measurement at only one pressure of about 390GPa by comparison with visual extrapolation, we perform SW experiments to replenish more T_m data on purpose to make this comparison more directly and rationally as well. The techniques adopted consist of Hügoniot sound velocity measurement for porous Mo and shock-induced release T_m measurements for both solid and porous Mo. Totally five SW T_m data, which extends the measured pressure range from previous about 390GPa down to about 136GPa that is close to the highest pressure (about 100GPa) attained by previous DAC experiments, are therefore obtained. These measured Tm data, other than the extrapolated as mentioned above, exhibit a manner of continuous variation with pressure and can be fitted well with Lindemann melting description. More significantly, the measured T_m data at lowest pressure are still much higher than that of the DACs and the overall trend of these T_m data is against to the two-segment melting curve model, with a sudden change in dT_m/d_P at about 210GPa, previously proposed by Errandonea Physica B 357 (2005) 356. Though the problem of large discrepancy in T_m data measured between DAC and SW has not been completely explained, our knowledge on this matter achieves indubitable progress since it is of value to programme the next clarification. Some suggestions for further clarifying the issue of large discrepancy between DAC and SW measurements are also proposed.