Molecular Dynamics Study of Short-Pulse Laser Melting, Recrystallization, Spallation, and Ablation of Metal Targets

Abstract

A hybrid computational model combining classical molecular dynamics method for simulation of fast nonequilibrium phase transformations with a continuum description of the laser excitation and subsequent relaxation of the conduction band electrons is developed. The model is applied for a systematic computational investigation of the mechanisms of short pulse laser interaction with bulk metal targets.The material response to laser irradiation is investigated in three regimes corresponding to the melting and resolidification of the surface region of the target, photomechanical spallation of a single or multiple layers/droplets, and ablation driven by the thermodynamic driving forces. The conditions leading to the transitions between the different regimes and the atomic-level characteristics of the involved processes are established.

Various damage mechanisms in carbon and silicon materials under femtosecond X-ray irradiation

“…Emergence of the diffraction peaks from the diffuse scattering pattern clearly shows some ordering in the structure before material disintegration. Then, material breaks apart into a few fragments, but not into atomic species, which is indicative of a spallation regime of the material removal rather than ablation 34 . Note that in contrast to a thin layer of C 60 here we modeled a bulk material with no open surfaces, and thus with no unbalanced charge in the system.…”

“…Molecular dynamics methods with classical potentials or force fields are among the most commonly used numerical tools for large-scale simulations in the solid-state modeling, see, e.g., [34][35][36] . Utilization of classical interatomic potentials makes MD simulations very efficient and capable of treating large systems 36,37 .…”

Atomistic Simulation Study of Short Pulse Laser-Induced Generation of Crystal Defects in Metal Targets

“…The results of these simulations were published in Ref. [119]. In order to bring to light the generation of the crystal defects in the regions that experienced transient melting and solidification, an additional structural analysis of the final configurations generated in these simulations is performed and the results of this …”

“…The concentration of point defects is also investigated for fcc Ni fcc targets is irradiated by short laser pulses at a broad range of absorbed laser fluences [119], in order to compare the concentration of vacancies/interstitials in two metals with different crystal structures. The difference in the concentration of vacancies is mainly related to two factors: (1) the slight differences in the energies of the vacancy formation between the two metals -the energy of the vacancy formation normalized by the thermal energy the melting point, eV [187]), and (2) the differences in the crystal structure between the close-packed fcc structure of Ni and a more open bcc structure of Cr.…”