The results of ab initio calculations and rate equation modeling of the early stages of oxide precipitation are compared with the results of highly sensitive Fourier transform infrared (FTIR) spectrometry of oxygen and vacancy oxygen containing complexes in silicon after rapid thermal annealing (RTA) treatment. The ab initio calculations have shown that the binding energy of interstitial oxygen in VOn is higher than in O-n for 1 <= n <= 6. For higher n, the energy gain is comparable. The point defect species O-1, O-2, O-3, and VO4 were detected by highly sensitive FTIR in high-oxygen Czochralski silicon wafers after RTA at 1250 degrees C. The concentrations obtained from kinetic simulations using an ab initio modeling approach for I, V, O-n with n = 1-4 and VOn with n = 1-8 without fitting parameters are in a good agreement with the experimental data for O-1, O-2, O-3, and VO4 as determined by highly sensitive FTIR. (C) 2011 The Electrochemical Society. [DOI: 10.1149/1.3543935] All rights reserved.