Large-scale molecular-dynamics simulations of martensitic nucleation and shape-memory effects in transition metal alloys

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Abstract
We discuss results of ab initio and molecular-dynamics simulations of structural phase transformations in magnetic transition metal alloys. In the simulations we make use of the embedded-atom method which allows to take into account the elastic behavior as well as phonon frequencies and vacancy-formation energy of the alloy under consideration. Also this method allows to simulate a large number of atoms required for the simulation of non-equilibrium phase transformations. Structural transformations are possible to simulate either by using the Parrinello scheme for a fluctuating volume box containing the atoms, or by using open boundary conditions. It is shown that structural transformations in the magnetic systems are different from corresponding transitions in the non-magnetic alloys. The simulations describe the large supercooling and superheating effect associated with the structural transformation as a function of the temperature and concentration as well as its dependence on lattice defects. In addition we show that also shape-memory effects can be simulated.