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DFT is nowadays the method of choice for large molecules
and extended systems, but standard LDA, GGA, and meta-GGA
functionals have problems for van der Waals interaction
and do not allow for a systematic improvement.
Part of these weaknesses can be overcome by restricting DFT to a short-range interelectronic interaction and using wavefunction-based ab-initio methods for the complementary long-range terms. It is shown that a both accurate and efficient treatment is possible at intermediate values of the coupling constant [1]. Still, application to extended systems necessitates a local correlation treatment on the ab-initio side. One of the simplest devices is a many-body expansion in terms of correlation contributions from localized orbital groups. Such an incremental expansion, on top of HF calculations, has proven to yield reliable results, at moderate cost, for a variety of solids (van der Waals crystals, ionic systems, semiconductors, and even metals) [2]. A possible application of the incremental method within a mixed DFT / ab-initio scheme will be discussed. [1] E. Goll, H.-J. Werner, H. Stoll, Phys. Chem. Chem. Phys. 7 (2005) 3917; E. Goll, H.-J. Werner, H. Stoll, T. Leininger, P. Gori-Giorgi, A. Savin, Chem. Phys. 329 (2006) 276. [2] H. Stoll, B. Paulus, P. Fulde, J. Chem. Phys 123 (2005) 144108; N. Gaston, B. Paulus, K. Rosciszewski, P. Schwerdtfeger, H. Stoll, Phys. Rev. B 74 (2006) 094102. |
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