Origin of anomalous lattice expansion in oxide nanoparticles

Abstract

The lattice constant change in oxide (ionic) nanoparticles originates from the variation in nominal ionic valences. The reduction of the valence induces an increase in the lattice constant due to the decrease in electrostatic forces, but the increase in the valence does not always lead to lattice shrinkage. Nanoparticles with the increase in ionicity or nominal valence may show either expansion or shrinkage, depending on the structure of the large clusters. Therefore, first-principles computer simulations of various kinds of large ionic clusters are necessary.