We present a multiscale model of GeSe2 glass structure, where interatomic potentials are calculated using Moller-Plesset perturbation theory and a cluster expansion approach. The ab initio calculations are fit to continuous functions and used in a classical Monte Carlo simulation of 1200 atoms. The resulting GeSe2 glass structure accurately captures the defect characteristics recently observed by a neutron diffraction experiment incorporating isotopic substitution. Our simulation results allow for further elaboration on the structure of deformed Ge-centered tetrahedra occurring in GeSe2 glass. This level of detail has not been captured by previous modeling efforts using density functional theory.