Hydrogen-bonded isomers of PH3–HF in the gas phase: theoretically comparative studies of geometry, vibrational frequency and interaction potential energy Original Research Article

Hydrogen-bonded isomers of PH3–HF in the gas phase have been studied by the Hartree–Fock ab initio, the various density-functional methods such as the hybrid-functionals B3PW91, B3LYP and its modified version M-B3LYP, and the generalized gradient approximation (GGA) functional PW91PW91, and the many-body Møller–Plesset perturbation formalisms (MP2 and MP3), using the standard split-valence 6-311++G(2d,2p) basis set. Three isomers of PH3–HF (I, II and III) have been proved as the stable ones on the potential-energy-surface, the linear one with C3v symmetry I is the most stable in the gas phase. Based on comparing the molecular properties and frequency shifts predicted at the present levels of theory with the experimental data available in the literatures, we find that the B3LYP and PW91PW91 methods are comparable with the good reliability of the MP2 formalism, while the M-B3LYP is not reliable for these weak hydrogen-bonded isomers.