Physical Review Letters ( IF 8.385 ) Pub Date :
Bernd Bauerhenne, Vladimir P. Lipp, Tobias Zier, Eeuwe S. Zijlstra, and Martin E. Garcia

Large-scale simulations using interatomic potentials provide deep insights in the processes occurring in solids subject to external perturbations. The atomistic description of laser-induced ultrafast nonthermal phenomena, however, constitutes a particularly difficult case and has so far not been possible on experimentally accessible length- and time scales because of two main reasons: (i) ab-initio simulations are restricted to a very small number of atoms and ultrashort times, and (ii) simulations relying on electronic temperature (${T}_{\mathrm{\text{e}}}$) dependent interatomic potentials do not reach the necessary ab-initio accuracy. Here we develop a self-learning method for constructing ${T}_{\mathrm{\text{e}}}$-dependent interatomic potentials which permit ultra-large scale atomistic simulations of systems suddenly brought to extreme nonthermal states with Density-Functional-Theory (DFT) accuracy. The method always finds the global minimum in the parameter space. We derived a highly accurate analytical ${T}_{\mathrm{\text{e}}}$-dependent interatomic potential, $\Phi \left({T}_{\mathrm{\text{e}}}\right)$, for silicon (Si), that yields a remarkably good description of laser excited and unexcited Si-bulk and Si-films. Using $\Phi \left({T}_{\mathrm{\text{e}}}\right)$ we simulate the laser excitation of Si nanoparticles and find strong damping of their breathing modes due to nonthermal melting.

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