Molecular dynamics simulations of the crystal–melt interfacial free energy and mobility in Mo and V

Abstract

Molecular dynamics simulations, based on embedded-atom method potentials, have been used to compute thermodynamic and kinetic properties of crystal–melt interfaces in the bcc metals Mo and V. The interfacial free energy and its associated crystalline anisotropy have been obtained with the capillary fluctuation method and for both metals the anisotropy and the value of the Turnbull coefficient are found to be significantly lower than for the case of fcc materials. The interface mobility, or kinetic coefficient, which relates the isothermal crystallization rate to interface undercooling, was computed by non-equilibrium molecular dynamics simulations. Mobilities in the range 9-16 cm s⁻¹K⁻¹ are obtained. For Mo the mobility in the (110) crystallographic growth direction is larger than in the (100) and (111) directions, whereas for V the growth is found to be isotropic within numerical uncertainty. The kinetic-coefficient results are discussed within the framework of a density-functional-based theory of crystal growth.

Acknowledgments

The authors would like to thank Professor B. B. Laird for providing the results of 57 prior to its publication. This research was supported by the US Department of Energy (DOE), Office of Basic Energy Sciences, under contract DE-FG02-01ER45910, as well as the DOE Computational Materials Science Network program. Use was made of resources at the National Energy Research Scientific Computing Center, which is supported by the Office of Science of the DOE under contract DE-AC03-76SF0098. Sandia is a multiprogram laboratory operated by Sandia Corporation, a Lockheed Martin Company, for the DOE's National Nuclear Security Administration under contract DE-AC04-94AL85000.