Nonequilibrium melting and crystallization of a model Lennard-Jones system

Abstract

Nonequilibrium melting and crystallization of a model Lennard-Jones system were investigated with molecular dynamics simulations to quantify the maximum superheating/supercooling at fixed pressure, and over-pressurization/over-depressurization at fixed temperature. The temperature and pressure hystereses were found to be equivalent with regard to the Gibbs free energy barrier for nucleation of liquid or solid. These results place upper bounds on hysteretic effects of solidification and melting in high heating- and strain-rate experiments such as shock wave loading and release. The authors also demonstrate that the equilibrium melting temperature at a given pressure can be obtained directly from temperatures at the maximum superheating and supercooling on the temperature hysteresis; this approach, called the hysteresis method, is a conceptually simple and computationally inexpensive alternative to solid-liquid coexistence simulation and thermodynamic integration methods, and should be regarded as a general method. We also found that the extent of maximum superheating/supercooling is weakly pressure dependent, and the solid-liquid interfacial energy increases with pressure. The Lindemann fractional root-mean-squared displacement of solid and liquid at equilibrium and extreme metastable states is quantified, and is predicted to remain constant (0.14) at high pressures for solid at the equilibrium melting temperature.

Simple calculation ofab initiomelting curves: Application to aluminum

“…From a practical viewpoint, since the ab initio molecular dynamics codes start usually from solid-state initial configurations, the simulations along the isotherms are conducted in a very similar way than in the hysteresis method [7]. Nevertheless, at contrast to the hysteresis method, the precise values of the limiting pressures, P s→l and P l→s , of the solid and liquid metastable phases is not required.…”

“…The obtained temperature corresponds rather at best to the highest temperature T h which can be reached by a superheated solid. Hysteresis [7]: HUM is supplemented by the reverse process, a liquid phase is cooled down to the lowest temperature T l , which can be reached by a supercooled liquid. An empirical average of the two temperatures, T h and T l , based on the homogeneous nucleation theory [8], gives an estimate of the true melting curve.…”

Molecular simulations of solid-liquid interfacial tension of silicon

“…10 Using a superheating/undercooling method in molecular simulation, 11 Luo et al simulated solid-liquid transitions of a LennardJones system 12 as well as water/ice system 13 and reported their solid-liquid interfacial tensions. In this short note, we apply the simulation method of Luo et al [11][12][13] to calculate solid-liquid interfacial tension of silicon.…”

Order-parameter-aided temperature-accelerated sampling for the exploration of crystal polymorphism and solid-liquid phase transitions

“…One estimate of the melting temperature has been reported for the same EAM potential. 72 In this study, a value of T m = 1300 ± 15 K was obtained using the superheating-supercooling hysteresis approach, 73 while T m was found to be 1350 ± 20 K with the two-phase method. Finally, an average of these two values, 1325 K, was used as the melting point in this study.…”