49 research outputs found
Microscopic mechanism of ultrashort-pulse laser ablation of metals: a molecular dynamics study incorporating electronic entropy effects
The microscopic mechanism of metal ablation induced by ultrashort laser pulse
irradiation is investigated. A two-temperature model scheme combined with
molecular dynamics (TTM-MD) is developed to incorporate electronic entropy
effects into the simulation of metal ablation while satisfying the energy
conservation law. Simulation with the TTM-MD scheme reveals that ultrashort
laser pulse irradiation near the ablation threshold causes high-energy ion
emission and sub-nanometer depth ablation, as observed experimentally, due to
the electronic entropy effect. It is also shown that the electronic entropy
effect is also significant in spallation.Comment: 13 pages, 18 figure
Accelerating Simulated Annealing of Glassy Materials with Data Assimilation
The ultra-long relaxation time of glass transition makes it difficult to
construct atomic models of amorphous materials by conventional methods. We
propose a novel method for building such atomic models using data assimilation
method by simulated annealing with an accurately computed interatomic potential
augmented by penalty from experimental data. The advantage of this method is
that not only can it reproduce experimental data as the structure refinement
methods like reverse Monte Carlo but also obtain the reasonable structure in
terms of interatomic potential energy. In addition, thanks to the interatomic
potential, we do not need high range diffraction data, which is necessary
to take into account the short-range order. Persistent homology analysis shows
that the amorphous ice obtained by the new method is indeed more ordered at
intermediate range