Impact of delocalized nonlinear vibrational modes on the properties of NiTi

OV Bachurina and AA Kudreyko and SV Dmitriev and DV Bachurin, PHYSICS LETTERS A, 555, 130769 (2025).

DOI: 10.1016/j.physleta.2025.130769

The behavior of twenty-five one-component three-dimensional DNVMs in the simple cubic titanium and nickel sublattices, and their influence on binary NiTi alloy properties, are studied using molecular dynamics simulations. Seventeen DNVMs exhibit stable time-periodic vibrations, while the remaining eight DNVMs are unstable. These unstable modes transfer vibrational energy between sublattices upon excitation. Most stable DNVMs exhibit a hard-type nonlinearity, where the frequency increases with increasing amplitude. Stable DNVMs can accumulate energy in the range of 0.1-1.0 eV per atom for both the nickel and titanium sublattices. The specific heat decreases (increases) for DNVMs with a hard (soft) type of nonlinearity. Excitation of DNVMs results in positive compressive stresses proportional to the displacement vector length. These results provide insight into the complex behavior of DNVMs in a binary NiTi alloy and their impact on material properties.

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