An empirical potential with fluctuating charges is proposed for modelling (MgO)_n clusters in both the molecular (small n) and bulk (n->infty) regimes. Vectorial polarization forces are explicitely taken into account in the self-consistent determination of the charges. Our model predicts cuboid cluster structures, in agreement with previous experimental and theoretical results. The effective charge transferred between magnesium and oxygen smoothly increases from 1 to 2, with an estimated crossover size above 300 MgO molecules.
@article{arxiv.cond-mat/0301440,
title = {Crossover between ionic/covalent and pure ionic bonding in magnesium oxyde clusters},
author = {F. Calvo},
journal= {arXiv preprint arXiv:cond-mat/0301440},
year = {2009}
}