Pressure and temperature dependence of diffusion coefficients in a model liquid and glass forming liquid

The self-diffusion coefficients in a model liquid and glass forming liquid have been studied as a function of temperature and pressure using the classical molecular dynamics (MD) method. Isothermal–isobaric (NPT) ensemble is carried out in our simulations. Special attention is paid to the glass-forming ability of the rapid-quench method under different pressures. We evaluate (1) glass transition and radial distribution function, (2) temperature dependence of diffusion coefficients in liquid and glass forming liquid, and (3) pressure dependence of diffusion coefficients in glass forming liquid. The simulations show (i) the greater the pressure, the higher the glass-transition temperature, by using the same high enough cooling rate from the melts; (ii) an Arrhenius dependence of diffusion coefficients D with reduced temperature T⁎ in liquid, that is, lnD~1/T⁎, and there being a process of slow change in glass forming liquid; (iii) an Arrhenius dependence of diffusion coefficients on pressure in glass forming liquid in the pressure range studied, that is, lnD~P⁎.