Diffusion Quantum Monte Carlo Calculation of the Austenite and Martensite Phases of NiTi

Kevin K Ly; Zhigang Wu; John W Lawson

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NASA NTRS · 20260005594

Diffusion Quantum Monte Carlo Calculation of the Austenite and Martensite Phases of NiTi

Kevin K Ly·Zhigang Wu·John W Lawson

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Abstract

NiTi is a promising material for smart and active technologies due to its exhibition of the shape memory effect, superelasticity, and biocompatibility. The shape memory effect is tied to the reversible transition between the austenite and martensite phases. A major research direction is to alloy NiTi with Zr, Hf, Pd, Pt, etc., in order to tune the martensitic transition temperature (MTT). Modeling the MTT from first principles is challenging because the lattice dynamics is complicated by anharmonicity and various low-energy structures. Using density functional theory, the energy difference between the austenite and martensite phases of NiTi varies by up to 100 meV/atom depending on the choice of density functional, which is of the same order of the energy difference itself. Consequently, free energy calculations with different functionals can result in estimates of the MTT that vary by several hundred K. Using diffusion quantum Monte Carlo, we calculated the energy difference between the B2 and B19' structures of NiTi to be 70.9 +- 2.5 meV/atom.

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Kevin K Ly, Zhigang Wu, John W Lawson. 2026-06-26. Diffusion Quantum Monte Carlo Calculation of the Austenite and Martensite Phases of NiTi. https://ntrs.nasa.gov/citations/20260005594

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