Correlated ab Initio Electronic Structure Calculations for Large Molecules

We discuss computational methods for carrying out correlated ab initio electronic structure calculations for large systems. The focus is on two types of methods: density functional theory (DFT) and localized orbital methods such as local MP2 (LMP2) and a multireference version based upon a generalized valence bond reference wave function, GVB-LMP2. The computational performance of both approaches using pseudospectral numerical methods is documented, and calculated thermochemical and conformational energetics are compared to experimental data.