NiTi₂, a New Liquid Glass

RF Tournier and MI Ojovan, MATERIALS, 16, 6681 (2023).

DOI: 10.3390/ma16206681

Many endothermic liquid-liquid transitions, occurring at a temperature Tn+ above the melting temperature T-m, are related to previous exothermic transitions, occurring at a temperature T-x after glass formation below T-g, with or without attached crystallization and predicted by the nonclassical homogenous nucleation equation. A new thermodynamic phase composed of broken bonds (configurons), driven by percolation thresholds, varying from similar to 0.145 to Delta epsilon, is formed at T-x,T- with a constant enthalpy up to Tn+. The liquid fraction Delta epsilon is a liquid glass up to Tn+. The solid phase contains glass and crystals. Molecular dynamics simulations are used to induce, in NiTi2, a reversible first-order transition by varying the temperature between 300 and 1000 K under a pressure of 1000 GPa. Cooling to 300 K, without applied pressure, shows the liquid glass presence with Delta epsilon = 0.22335 as memory effect and Tn+ = 2120 K for T-m = 1257 K.

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