Berlin 2012 – wissenschaftliches Programm

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TT: Fachverband Tiefe Temperaturen

TT 19: Correlated Electrons: (General) Theory 2

TT 19.11: Vortrag

Dienstag, 27. März 2012, 12:30–12:45, H 3010

Application of wave function based electron correlation methods to van der Waals bound crystals — •Carsten Müller¹ and Denis Usvyat² — ¹Institut für Chemie und Biochemie, Freie Universität Berlin Takustr. 3, Berlin, 14195, Germany — ²Institut für Physikalische und Theoretische Chemie, Universität Regensburg Universitätsstr. 31, Regensburg, 93040, Germany

The treatment of van der Waals bound systems, such as molecular crystals is a remains challenging in theoretical solid state chemistry. In these systems, electron correlation is crucial and HF or standard DFT functionals often fail to produce reliable cohesive energies. On the other hand, common implementations of wave function based post-HF methods, such as MP2 or Coupled Cluster theory, suffer from an unfortunate scaling with system size, and are difficult to adopt to periodic systems.

In our investigations we have combined the Method of Increments, which is one type of local correlation method, with embedded cluster calculations to investigate physisorption Ar fcc and the CO₂ crystal at the LMP2 and LCCSD(T) levels. First, periodic LMP2 calculations were performed to obtain appropriate parameters for the size of the excitation domains and to assess the convergence of the incremental expansion. Then different schemes for the embedding of the finite clusters were assessed for their influence on the convergence behavior of the incremental expansion. And finally calculations at the LCCSD(T) level and with larger basis sets were used to obtain the cohesive energy of Ar fcc and CO₂ with benchmarking quality.