Ab initio characterization of the ion P2O+

The structures, frequencies and thermochemistry of isomers of P2O+ and its parent neutral molecule have been calculated using multiconfigurational self-consistent field and augmented coupled-cluster techniques together with large basis sets of spdf and spdfg quality. Our results appear to be the best currently available. Whereas neutral P2O has a linear structure as the global minimum, the cyclic structure of P2O+ is predicted to be lower in energy than linear P2O+ by about 26 kcal/mol. Our calculations of neutral P2O, for which we obtain excellent agreement with experimental results, should provide a calibration of our P2O+ results. As expected, P2O+ dissociates preferentially to PO+ + P fragments.