15min:

D. E. WOON AND T. H. DUNNING JR., Department of Chemistry, University of Illinois at Urbana-Champaign, Urbana, IL 61801.

Structures of the PF_n family (n=1--5) were characterized with high level RCCSD(T) coupled cluster theory calculations using triple and quadruple zeta quality correlation consistent basis sets. In addition to accounting for the well-known ground states of PF through PF₅, insight from the recoupled pair bonding model also led to locating a previously unknown ³B₁ state of PF₃, which lies about 90 kcal/mol above PF₃(¹A₁) but is still bound with respect to PF₂(²B₁)+F(²P) by about 40 kcal/mol. We also revisited the less-studied C_3v local minimum on the PF₄ doublet surface and characterized the transition state for interconversion to the C_2v global minimum. The energetics suggest that both PF₃(³B₁) and C_3v PF₄(²A₁) are potentially observable in the laboratory. The trends in the bond dissociation energies and relative energy differences of the PF_n family are very consistent with predictions from the recoupled pair bonding model.