Abstract
Laser ablation is often simulated by the two-temperature model in which electrons are assumed to be thermalized by laser irradiation, while an explicit representation of interaction between laser-field and electrons is challenging but beneficial as being free from any adjustable parameters. Here, an ab initio method based on the time-dependent density functional theory (TDDFT) in which electron-ion dynamics under a laser field are numerically simulated is examined as a tool for simulating femtosecond laser processing of metals. Laser-induced volume expansion in surface normal directions of Cu(111) and Ni(111) surfaces are simulated by using repeating slab models. The amount of simulated volume expansion is compared between Cu(111) and Ni(111) slabs for the same laser pulse conditions, and the Ni slab is found to expand more than the Cu slab despite the smaller thermal expansion coefficient of Ni compared with Cu. The analyzed electronic excitation and lattice motion were compared to those in the two-temperature model. The threshold fluence to release surface Cu atom deduced from current TDDFT approach is found to be comparable to those of Cu ablation reported experimentally.
Highlights
Laser ablation is often simulated by the two-temperature model in which electrons are assumed to be thermalized by laser irradiation, while an explicit representation of interaction between laser-field and electrons is challenging but beneficial as being free from any adjustable parameters
The present study aims to simulate femtosecond laser processing of metals deductively from ab initio simulation starting with an explicit representation of interaction between laser-field and electrons and subsequent molecular dynamics instead of employing electron temperature
There still remains a gap between atomic-scale phenomena and macroscopic-scale phenomena, the first step toward simulating femtosecond laser processing is to monitor the volume expansion and release of surface atoms of metals by using conventional repeating slab models representing metal surfaces
Summary
Laser ablation is often simulated by the two-temperature model in which electrons are assumed to be thermalized by laser irradiation, while an explicit representation of interaction between laser-field and electrons is challenging but beneficial as being free from any adjustable parameters. In the two-temperature model, laser-induced excitation and subsequent lattice dynamics are simulated by an equation for heat transport from electrons to the lattice which uses parameters such as the heat capacities of electrons and the lattice as well as an electron-lattice coupling c onstant[13,17,20]. This model has been applied to laser ablation of Cu by combining experimental and theoretical a pproaches[21]. This is referred to as TDDFT-MD simulation in the rest of this manuscript
Sign-in/Register to view highlights & summary Sign-in/Register to access full text options 
Free) 
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a call
