Shock melting method to determine melting curve by molecular dynamics: Cu, Pd, and Al

Abstract

A melting simulation method, the shock melting (SM) method, is proposed and proved to be able to determine the melting curves of materials accurately and efficiently. The SM method, which is based on the multi-scale shock technique, determines melting curves by preheating and/or prepressurizing materials before shock. This strategy was extensively verified using both classical and ab initio molecular dynamics (MD). First, the SM method yielded the same satisfactory melting curve of Cu with only 360 atoms using classical MD, compared to the results from the Z-method and the two-phase coexistence method. Then, it also produced a satisfactory melting curve of Pd with only 756 atoms. Finally, the SM method combined with ab initio MD cheaply achieved a good melting curve of Al with only 180 atoms, which agrees well with the experimental data and the calculated results from other methods. It turned out that the SM method is an alternative efficient method for calculating the melting curves of materials.

Comparative Study on Two Melting Simulation Methods: Melting Curve of Gold

“…In order to crosscheck the results and compare the efficiencies, we calculate the melting curve of Au using the TP method [21] and the SM method. [7] In the TP simulations, we build an initial configuration with a solid-liquid interface (Fig. 3).…”

“…[6] However, the high-pressure melting curve is still absent up to now. As the melting curve presents a natural up-limit of temperature of Au as a pressure calibrator, we here have a detailed study on the high-pressure melting curve of Au using our recently developed shock melting (SM) method [7] and the popular TP method to have a crosscheck. Meanwhile, the results from the two method are also compared and the SM method is found to be very efficient and time-saving.…”

Melting Is Well-Known, but Is It Also Well-Understood?

“…Further efficiency can be obtained by using the shock melting method, 177 based on the multiscale shock techni-que, 178 in which shock loading is done to drive the simulated system to the final Hugoniot end state. Shocking a sample with the shock velocity U, the multiscale shock technique keeps it on both the Rayleigh line P − P 0 = U 2 [1 − (ρ 0 /ρ)]/ρ 0 and the shock Hugoniot state U − U 0 = 1/2(P + P 0 )(V 0 − V) by applying a uniaxial strain to the computational cell.…”

“…In such a simulation, with conservation of mass, momentum, and energy, the Hugoniot end state of the simulated system is achieved by adjusting V and T iteratively, and this end state was shown to be consistent with results of nonequilibrium MD simulations. 177,178 A comparative study using the shock method and the two-phase method for Au using an embedded atom potential 179 illustrated that, while obtaining comparable results, the number of atoms to be used in the shock method can be considerably smaller than that used for the two-phase method (as long as one is not interested in the details of the shock wave process itself). For example, in this calculation the twophase method used 20 736 atoms, while the shock method employed only 640 atoms, nevertheless obtaining virtually the same result.…”

Molecular dynamics simulation of shock wave propagation and spall failure in single crystal copper under cylindrical impact

“…Classical molecular dynamics (MD) simulations are suited for studies on shock melting and provide powerful tools to reveal the atomic-scale detail of solid-liquid phase transformations. 4) For fcc crystals, impact-induced melting exhibits strong anisotropy. [5][6][7] For example, for 〈100〉 shocks, the copper undergoes a state of overheating, while for the 〈110〉 and 〈111〉 shocks, a premelting phenomenon, partial melting at a temperature below the equilibrium melting point, is observed.…”