Large basis set calculations using Brueckner theory

Calculations are reported using the Brueckner doubles method, with and without a perturbative estimate of the effects of triple excitations, and using basis sets which are at least triple zeta with two sets of polarization functions in quality. Equilibrium geometries and harmonic vibrational frequencies are calculated for HF, N2, H2O, NH3, CH4, HCN, H2CO, NNO, and O3. Comparison with experimental data confirm the high accuracy of Brueckner methods.