Analytic gradients for the combined sr-DFT/lr-MP2 method: application to weakly bound systems

The formalism for analytical gradients in short-range density functional schemes with long-range ab initio corrections (sr-DFT/lr-ab initio) is presented. On the density-functional side, both sr-LDA and sr-PBE are available, while on the ab initio side lr-HF and lr-MP2 are possible. Details of the implementation in the Molpro package are given. Results from test calculations using different basis sets on weakly bound systems of the HB6/04, DI6/04, CT7/04 and WI9/04 databases are presented.