Bonding and electronic properties of non-stoichiometric lithium oxide
clusters LinO2 (n less than or equal to 10) are studied by means of ab
initio simulations. We focus on the first stage of lithium enrichment
of stoichiometric Li4O2, where the formation of additional Li-O bonds
is favoured. The bonding configuration of the lowest-energy isomers a
nd their stability are analysed in detail, and their structures compar
ed to those found in bulk non-stoichiometric alkali-metal suboxides. A
s a function of the increasing number of excess Li atoms, coexistence
of an ionic and a delocalized character of the electronic density take
s place, accompanied by a progressive Li-O bond weakening. These issue
s, and the existence of odd-even staggering of electronic properties,
are discussed, in relation to recent experiments and other anion-defic
ient systems such as defective oxide surfaces and alkali-metal halide
clusters.