Ab initio-based Monte Carlo and mean field studies of phase separated alpha NiSn (alpha =Ti1-xHfx, Ti1-xZrx, Hf1-xZrx) compounds with C1(b) structure

作者：Mena Joaquin Miranda^*; Schoberth Heiko G; Gruhn Thomas; Emmerich Heike

来源：Acta Materialia, 2016, 111: 157-165.

DOI：10.1016/j.actamat.2016.03.036

• Ab initio calculations
• Thermoelectric materials
• Heusler alloys
• Phase separation
• Monte Carlo simulation

We combine Density Functional Theory calculations, Monte Carlo simulations and mean field models to study the thermodynamic conditions for phase separation in alpha NiSn (alpha = Ti1-xHfx, Ti1-x-Zr-x, Hf1-xZrx). Density functional theory results show that Ti and Hf (Zr) atoms prefer to form nano-domains. This tendency is studied on larger scale and at finite temperatures with the help of Monte Carlo simulation; here for a wide range of concentrations, Ti-rich regions coexist with Ti-poor regions below the critical temperature T*. In the alloy NiTi1-x HfxSn T* approximate to 500 K and for NiTi1-xZrxSn T* approximate to 900 K. However, the phenomenon is not present when alloying Hf and Zr. We complement these two scale methods with a mean field model that help us to construct the phase diagram of the materials. We discuss these results in the view of thermoelectrics, where multidomains enhance the figure of merit. Our assessment of the material at the scale of 200 nm yields information about the interface structure which is relevant for the thermal conductivity.

• 出版日期2016-6-1