THE DISSOCIATION-ENERGIES OF NF(X(3)SIGMA(-)) AND NCL(X(3)SIGMA(-))

We have computed potential energy functions for the ground states (X ( 3) Sigma(-)) of NF and NCl using a series of correlation consistent ba sis sets ranging from double to sextuple zeta quality and including co re-valence correlation effects in conjunction with coupled-cluster sin gle and double excitations with perturbative treatment of triple excit ations [CCSD(T)] and large internally contracted multireference config uration interaction (icMRCI) wave functions. The best estimates for th e dissociation energies (D-e's) are 76.6+/-1.3 kcal/mol for NF and 64. 6+/-1.3 kcal/mol for NCl, respectively. Our results suggest that previ ous experimental estimates for the dissociation energy of NCl are in e rror by as much as 15 kcal/mol. The calculated spectroscopic constants for NF and NCl are in good agreement with the measured constants. (C) 1997 American Institute of Physics.