Short-range density functionals in combination with local long-range ab initio methods: Application to non-bonded complexes

Within this work, we introduce local-correlation approximations into a hybrid approach which couples short-range density functional-based with long-range wave-function-based methods. The local treatment of long-range ab initio correlation is expected to greatly enhance the efficiency of the mixed approach for large systems. We start from our previous implementation, where a short-range gradient-corrected density functional of the Perdew-Burke-Ernzerhof (PBE) type is coupled with long-range Moller-Plesset second order perturbation theory and coupled-cluster methods, and extend the scheme to include the corresponding local long-range ab initio methods. The accuracy of the resulting approach is tested using the benchmark database for non-bonded (or, more precisely, weakly bonded) interactions of Zhao and Truhlar. The effect of the local-correlation approximation as well as the influence of counterpoise corrections is discussed for the different types of methods. It is shown that the mixed short-range/long-range approach is less sensitive to the ab initio correlation level and the one-particle basis-set used than pure ab initio methods, while the overall performance is significantly improved with respect to pure PBE. (C) 2008 Elsevier B.V. All rights reserved.