Correlated ab initio electronic structure calculations for large molecules

We discuss computational methods for carrying out correlated ab initio elec tronic structure calculations for large systems. The focus is on two types of methods: density functional theory (DFT) and localized orbital methods s uch as local MP2 (LMP2) and a multireference version based upon a generaliz ed valence bond reference wave function, GVB-LMP2. The computational perfor mance of both approaches using pseudospectral numerical methods is document ed, and calculated thermochemical and conformational energetics are compare d to experimental data.