Anton Van der Ven

Jon G. Goiri, Naga Sri Harsha Gunda, Elizabeth Decolvenaere, Daniil Kitchaev, Anirudh R. Natarajan

Materials Department, University of California Santa Barbara

First-principles statistical mechanics of diffusion, magnetism and interstitial-solute interactions in disordered alloys

Chemical disorder in alloys poses challenges to modeling a wide variety of properties at finite temperature. A diffusing atom, for example, will sample many different local environments as it wanders through a disordered alloy, resulting in a spectrum of different migration barriers. This can lead to correlations between successive hops that affect macroscopic transport coefficients. Disorder among magnetic elements complicates a description of magnetic properties as the magnetic interactions become dependent on local composition and degree of disorder. Chemical disorder becomes even more complicated in metals that are able to dissolve high concentrations of interstitial species. This is especially true in early refractory metals (Ti, Zr, Hf, V, Nb, Ta) which are able to dissolve C, N and O. Interesting short and long-range ordering tendencies can emerge between interstitial elements and substitutional solutes. First-principles statistical mechanics methods based on the cluster expansion approach are able to shed light on the effect of chemical disorder on finite temperature properties. In this talk I will describe how these tools can be used to predict phase diagrams, diffusion coefficients and magnetic properties of multi-component alloys.  The statistical mechanics approaches rely on effective Hamiltonians to extrapolate first-principles electronic structure methods within Monte Carlo simulations.

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