We model Si 2p core-level shifts at Si-(ZrO2)(x)(SiO2)(1-x) interfaces for varying Zr content x. Using a first-principles approach, we calculate Si 2p shifts for a model interface and for cluster models, and establish the validity of a linear dependence of these shifts on both the number of second-neighbor Zr atoms and the O coordination of these Zr atoms. Applying this relation to model structures of amorphous Zr silicates generated by classical molecular dynamics, we find that the Si 2p line shifts to lower binding energies with increasing Zr content x, in accord with experimental data. (C) 2002 American Institute of Physics.