Damage dynamics simulations of Pt film irradiation by XFEL femtosecond pulses.

The reflective mirror coating materials of free electron laser devices are prone to damage under extreme irradiation conditions, which seriously restrict the operation efficiency and lifespan of the devices. Therefore, clarifying the damage mechanism under specific conditions is beneficial for the selection and design of incident parameters. Based on the two-temperature model and molecular dynamics simulation method, it investigates the damage dynamic behavior of Pt as a reflective mirror film material under X-ray free electron laser femtosecond pulse irradiation, especially the phase explosion damage at supra-threshold energy density. The research has found that at low energy density, the rupture of the film layer begins with the surface atoms, which is driven by stress waves and leads to macroscopic fracture. At high energy density, the accumulation of energy within the film layer triggers an explosive transformation from a gas-liquid mixture to a phase explosion. It reveals the complexity of film damage under extreme conditions, providing a theoretical basis for the process optimization of high-energy irradiation.