Unoccupied oxygen p-projected densities of states, calculated from first pr
inciples in a model Si/SiO2 interface, are found to reproduce trends in rec
ent atomic resolution electron energy-loss spectra [D-A. Muller et al., Nat
ure (London) 399, 758 (1999)]. The shape of the unoccupied states and the m
agnitude of the local energy gap are explicitly related to the number of O
second neighbors of a given oxygen atom. The calculated local energy gaps o
f the oxide become considerably smaller within 0.5 nm of the interface, sug
gesting that the electronic properties do not change abruptly at the interf
ace.