Structural transformations at high pressure in the refractory metals (Ta, Mo, V)

• The model of the elastic phase transitions under high pressures was developed and applied.
• Elastic constants and phonon dispersion curves of V, Ta and Mo under pressure were calculated.
• Structural stability of V, Ta and Mo under pressure was theoretically investigated.
• The bcc-rhombahedral phase transition in V was found to be an elastic phase transitions.
• The softening of the elastic constants C̃′ of Mo under P > 500 GPa was found.

In the framework of the Landau theory, the elastic phase transitions under pressure in metals with a cubic lattice are considered. The model of such transitions is proposed. Conditions for the loss of stability of a cubic crystal under hydrostatic pressure are obtained. The effective elastic constants of second, third and forth orders and phonon dispersion of V, Mo and Ta in wide range of pressure were calculated by the density functional theory. The stability of bcc lattice and structural transformations in these metals are investigated on base of the obtained data.