Collective atomic displacements during complex phase boundary migration in solid-solid phase transformations
J. Duncan, A. N. Harjunmaa, R. Terrell, R. Drautz, G. Henkelman, J. Rogal.
The A15 to bcc phase transition is simulated at the atomic scale based on an interatomic potential for molybdenum. The migration of the phase boundary proceeds via long-range collective displacements of entire groups of atoms across the interface. To capture the kinetics of these complex atomic rearrangements over extended time scales we use the adaptive kinetic Monte Carlo approach. An effective barrier of 0.5 eV is determined for the formation of each new bcc layer. This barrier is not associated with any particular atomistic process that governs the dynamics of the phase boundary migration. Instead, the effective layer transformation barrier represents a collective property of the complex potential energy surface.
Left: Change in energy during the transformation from A15 to BCC in molybdenum along an adaptive kinetic Monte Carlo trajectory at T=300K. Right: Representation of the energy states that are visited along a trajectory in a disconnectivity graph.