NiTi₂, a New Liquid Glass

Area of Science:

• Materials Science
• Thermodynamics
• Computational Chemistry

Background:

• Liquid-liquid transitions are often preceded by exothermic events and followed by endothermic transitions above melting temperatures.
• These transitions are linked to glass formation and can involve crystallization, predicted by nonclassical nucleation theories.

Purpose of the Study:

• To investigate the thermodynamic nature of liquid-liquid transitions and the formation of a novel phase.
• To explore the role of broken bonds (configurons) and percolation thresholds in these transitions.
• To demonstrate the reversible nature of these transitions using molecular dynamics simulations.

Main Methods:

• Utilized molecular dynamics simulations to study NiTi2 under high pressure (1000 GPa) and varying temperatures (300-1000 K).
• Induce reversible first-order phase transitions by manipulating temperature and pressure.
• Analyzed the formation of a new thermodynamic phase (configurons) and its properties.

Main Results:

• Identified a new thermodynamic phase composed of 'configurons' (broken bonds) formed at Tx, with constant enthalpy up to Tn+.
• Observed a liquid glass fraction (Δε) that persists up to Tn+.
• Demonstrated a reversible first-order transition in NiTi2, with a memory effect observed upon cooling, showing liquid glass presence (Δε = 0.22335) and predicted Tn+ = 2120 K for Tm = 1257 K.

Conclusions:

• The study establishes the existence and characteristics of a new thermodynamic phase (configurons) related to liquid-liquid transitions.
• The findings highlight the role of percolation and broken bonds in driving these transitions.
• The memory effect observed in NiTi2 underscores the complex thermodynamic behavior of materials under extreme conditions.