Ab-initio study of early-stage carbon plasma formation from short-pulse laser irradiation

Irradiating carbon targets with an intense short-pulse laser induces extreme conditions in the material and produces plasma. Understanding the physics of carbon plasma formation is essential for Inertial Confinement Fusion concepts and extensive aspects of astrophysics. However, the fundamental principles of plasma formation and dynamics remains unclarified since direct experimental study is very challenging, and widely used kinetic method starts with formed plasma. Here, we use ab initio methods to investigate the early stages of carbon plasma formation from the laser-irradiated graphene and diamond. First, molecular dynamics electronic structure calculations using the electronic temperature (T_e) dependent density functional theory code, CHIVES, were performed. By varying the initial T_e and thermalizing the atoms, key parameters such as electronic density of states (eDOS), ionic motion and energy are calculated. Plasma formation is then identified by the evolution of the eDOS toward a free electron-like state, enabling us to extract the critical time and temperatures associated with the transition. Finally, the first-principles calculated electron energy distribution is used as input for further kinetic calculationson on larger temporal and spatial scales with a particle-in-cell code, WarpX. This work offers a novel point of view on early-stage carbon plasma formation and elucidates the impact of initial atomic configuration during this process.