Benchmark calculations with correlated molecular wave functions. II. Configuration interaction calculations on first row diatomic hydrides

Abstract

Potential energy functions have been calculated for the electronic ground states of the first row diatomic hydrides BH, CH, NH, OH, and HF using single- (HF+1+2) and multi- (GVB+1+2 and CAS+1+2) reference internally contracted single and double excitation configuration interaction (CI) wave functions. The convergence of the derived spectroscopic constants and dissociation energies with respect to systematic increases in the size of the one-particle basis set has been investigated for each method using the correlation consistent basis sets of Dunning and co-workers. The effect of augmenting the basis sets with extra diffuse functions has also been addressed. Using sets of double (cc-pVDZ) through quintuple (cc-pV5Z) zeta quality, the complete basis set (CBS) limits for Ee, De, re, and ωe have been estimated for each theoretical method by taking advantage of the regular convergence behavior. The estimated CBS limits are compared to the available experimental results, and the intrinsic errors associated with each theoretical method are discussed. The potential energy functions obtained from GVB+1+2 and CAS+1+2 calculations are observed to yield very comparable spectroscopic constants, with errors in De ranging from 0.4 kcal/mol for BH to 2.9 kcal/mol for HF. The contraction errors associated with the internally contracted multireference CI have also been calculated for each species; while found to increase from BH to HF, they are, in general, small for all calculated spectroscopic constants. For the cc-pVDZ basis sets, spectroscopic constants have also been determined from full CI calculations.