Abstract
We discuss two procedures to obtain empirical potentials from ab initio trajectories. The first methodconsists in adjusting the parameters of an empirical pair potential so that the radial distribution functionsextracted from classical simulations using this potential match the ones extracted from the ab initio sim-ulations. As a case study, we consider the example of amorphous silica, a material that is highly relevantin the field of glass science as well as in geology. With our approach we are able to obtain an empiricalpotential that gives a better description with respect to structural and thermodynamic properties thanthe potential proposed by van Beest, Kramer, and van Santen, and that has been very frequently usedas a model for amorphous silica. The second method is the so-called ‘‘force matching” approach proposedby Ercolessi and Adams to obtain an empirical potential. We demonstrate that for the case of silica thismethod does not yield a reliable potential and discuss the likely origin for this failure.