Basis set error in quadrupole moment calculations

Abstract

For a series of first row diatomic molecules, quadrupole moments obtained from restricted Hartree-Fock level calculations with various basis sets are compared with exact values obtained from numerical solution of the Hartree-Fock equations. Significant basis set errors are frequently observed, even with large and/or exponent optimized basis sets. Estimates of the correlation errors in the quadrupole moments lead to the conclusion that basis set error is probably just as serious as correlation error for most molecular quadrupole moment calculations.