Accuracy of mixed Gaussian lobe basis sets used for molecular calculations

Mixed Gaussian basis sets of double zeta accuracy have been previously used to allow excellent approximations to the energy and one-electron properties for molecular systems to be calculated with a considerable economy in computational labour. Here we show that these mixed basis sets also allow the calculation of accurate ESCA binding energies using either the ?sudden? or ?adiabatic? approximations. The basis sets are not recommended for the calculation of molecular geometries. ��� We have also tested some smaller mixed basis sets and find quite large variations in the calculated one-electron expectation values compared with those calculated using double zeta accuracy mixed basis sets.