arXiv subjects

Simon Kümmel

Publications and source records attributed to Simon Kümmel.

3 recordsLinked to original sources

arXiv2026

Energy conservation and pressure relaxation in an extended two-temperature model for copper with an electron temperature-dependent interaction potential

An implementation of an electron temperature-dependent interaction potential for copper in a two-temperature model-molecular dynamics framework is presented. An algorithm for enforcing energy conservation when using such an interaction is provided that is needed due to the changing interaction strength with the degree of excitation. Furthermore, focus is put on how to treat the pressure differences due to an electron temperature gradient following laser irradiation. The influence of various extensions is investigated in large-scale two-temperature model molecular dynamics simulations and compared to existing approaches.

cond-mat.mtrl-sci↗

arXiv2026

Novel non-thermal Ablation Mechanics in the Laser Ablation of Silicon

We investigate the non-thermal material dynamics of strongly excited silicon during ultra-fast laser ablation. In contrast to metals, silicon shows strongly excitation-dependent interatomic bonding strengths, which gives rise to a number of unique material dynamics like non-thermal melting, Coulomb explosions and altered carrier heat conduction due to charge carrier confinement. In this study, we report novel non-thermal ablation mechanisms in the ultra-fast single shot laser ablation of silicon and perform large scale massive multi-parallel simulations on experimentally achievable length scales with atomistic resolution. For this, we model the ultra-fast carrier dynamics utilizing the Thermal-Spike-Model coupled to Molecular Dynamics simulations and include the accompanied excitation-dependent nonthermal bonding strength manipulation by application of the excitation-dependent modified Tersoff Potential. Further, we present first results on the systematic construction of the excitation-dependent phase diagram of silicon by thermodynamic integration.

cond-mat.mtrl-sci↗

arXiv2025

Development and validation of an electron temperature-dependent interaction potential for silicon and copper for the use in atomistic simulations of laser ablation

Laser pulses with a duration of the order of femtoseconds lead to a strong excitation, heating and potentially to ablation of the irradiated material. During the time of strong excitation, the interaction of the atoms and thus the material dynamics can be strongly altered. To take this effect into account, an ip was developed for copper that takes the excitation of the electrons into account up to an electron temperature of 1.2 eV. Furthermore, several ways to identify non-thermal effects in Density Functional Theory calculations and how to incorporate and validate them in molecular dynamics simulations are presented. Explicitly, the free energy curves, elastic constants and phonon spectra are compared. Additionally, it is shown that the change of the melting temperature with the degree of excitation is consistent with all of these properties. Moreover, the behaviour of copper upon excitation is compared to silicon by using a similar potential that was previously developed by a different author.

cond-mat.mtrl-sci↗