On the convergence ofMBPT andCC nuclear magnetic shielding constants ofBH toward the fullCI limit

Abstract

The performance of many-body perturbation theory (MBPT) and coupled-cluster (CC) methods in the calculation of nuclear magnetic shielding constants for BH is analyzed by comparison with results from full configuration interaction (FCI) calculations. Low-order MBPT computations are shown to be inadequate for BH, while the coupled-cluster ansatz, in particular, in its singles and doubles (CCSD) approximation, provides an efficient treatment of electron correlation, overestimating correlation effects to the 11B shielding by only 3-4 ppm (1.5%). Based on this comparison, CCSD calculations with large atomic natural orbital (ANO) basis sets are used to estimate accurate theoretical values for the isotropic and anisotropic shielding constants of BH. © 1995 John Wiley & Sons, Inc.