The glass transition and diffusion in simulated liquid TiO₂

Area of Science:

• Materials Science
• Computational Chemistry
• Condensed Matter Physics

Background:

• Understanding the behavior of liquid titanium dioxide (TiO2) is crucial for various high-temperature applications.
• Previous studies have explored its structural and dynamic properties, but a comprehensive understanding of its phase transitions and diffusion mechanisms under varying conditions remains incomplete.

Purpose of the Study:

• To investigate the glass transition and atomic diffusion in liquid TiO2 using molecular dynamics simulations.
• To determine the density dependence of the glass transition temperature (Tg).
• To analyze the temperature and density effects on diffusion coefficients and structural transitions.

Main Methods:

• Employing molecular dynamics (MD) simulations with a model containing 3000 atoms.
• Simulating liquid TiO2 across a wide temperature range (2100–7000 K) and densities (3.80–4.20 g cm−3).
• Analyzing the temperature dependence of diffusion constants and structural differences at varying densities.

Main Results:

• The density dependence of the glass transition temperature (Tg) for liquid TiO2 was determined.
• Diffusion constants followed an Arrhenius law at lower temperatures but deviated at higher temperatures.
• Distinct structural differences were observed between amorphous TiO2 models at different densities.
• A transition from a low-density liquid (ldl) to a high-density liquid (hdl) form was identified.

Conclusions:

• The study provides insights into the complex phase behavior of liquid TiO2, including its glass transition and diffusion characteristics.
• The findings highlight the influence of density and temperature on TiO2's structural and dynamic properties.
• The observed liquid-liquid transition offers a new perspective on the phase diagram of titanium dioxide.