Efficient modeling of metal ablation irradiated by femtosecond laser via simplified two-temperature model coupling molecular dynamics

A simplified two-temperature model coupling molecular dynamics (TTM-MD) method is proposed to study the femtosecond laser ablation of metal, which can simulate a micron-sized laser spot irradiation under the premise of atomic-level calculation accuracy. The theoretical TTM-MD model is re-derived using the Langevin equation to reduce the calculation frequency of lattice temperature and improve the solution efficiency. Then, the TTM-MD simulation model is simplified to a one-dimensional model according to the rotational symmetry of laser spot and neglecting the lateral heat transfer. The temperature variation, pressure evolution, and void nucleation are analyzed to reveal the spallation and explosion ablation regimes. The variation of simulated ablation depth with laser fluence is consistent with the experimental results. The full-sized crater profiles predicted by this simplified model also match well with the ablation experiments irradiated by the Gaussian laser spot. Moreover, the step boundary caused by the threshold effect of laser ablation also can be captured on the crater edge. These results suggest that the proposed model provides essential insight into the femtosecond laser ablation by avoiding the limitation of current computing power.