Abstract
We present quantum molecular dynamics calculations of thermophysical properties of solid and liquid molybdenum in the vicinity of melting. Detailed analysis of available experimental isobaric expansion data and extensive comparison over a wide set of properties with results of first-principle calculations is presented, possible reasons of contradictions are discussed. Accurate calculation of zero isobar confirms the density of solid Mo measured by electrostatic levitation technique and the lowest density of molten Mo observed in pulse heating experiments, that gives a substantial volume change on melting of about 5.5%.
Highlights
Refractory metals are of great importance because of their unique and desirable properties
An estimate of Shaner et al.[52] is 33.3 K/GPa. As it have been shown in this work, molybdenum is still one of the most complex metals for experimental and theoretical study, its thermophysical properties in vicinity of melting are highly ambiguous due to strong contradictions in available experimental data
In the solid phase the results of the first-principle calculations agree perfectly with the density measurements of Mo by the electrostatic levitation technique, while for liquid Mo excellent agreement is achieved with the measurements by the microsecond pulse heating technique by the group of the University of Technology of Graz (Pottlacher et al, Hupf et al.)
Summary
Refractory metals are of great importance because of their unique and desirable properties. The second technique is fast resistive pulse heating, in which a sample (wire, strips, etc.) is uniformly self-heated by electric current for a short period of time by the Joule effect This approach minimises effects of thermal and chemical reactions with the surrounding medium and allows to reach much higher temperature ranges (up to 10 kK). Like many of the transition metals, it has a complex electronic structure that leads to the variety of unusual physical effects, like a positive sign of Seebeck and Hall coefficient near the ambient conditions, anomalous self-diffusion behaviour near the melting point,[12] dynamical stabilization of the crystal structure at high temperature by anharmonic effects,[13] etc This fact makes it virtually impossible to create an adequate analytic model of thermophysical properties of hot expanded molybdenum.[14]. A detailed analysis of available experimental isobaric expansion data and extensive comparison over a wide set of properties with results of first-principle calculations is presented, possible reasons of contradictions are discussed
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