The results of highly sensitive FTIR investigation, ab initio calculations and rate equation modeling of the early stages of oxide precipitation are compared. The attachment of interstitial oxygen to VOn is energetically more favorable than the attachment to On for n 6. For higher n the energy gain is comparable. The point defect species which were detected by highly sensitive FTIR in high oxygen Czochralski silicon wafers are O1, O2, O3, and VO4. Rate equation modeling for I, V, On and VOn with n = (1..4) also yields O1, O2, O3 to appear with decreasing concentration and VO4 as that one of the VOn species which would appear in the highest concentration after RTA.