Berlin 2015 – scientific programme

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TT: Fachverband Tiefe Temperaturen

TT 106: Frontiers of Electronic Structure Theory: Many-Body Effects, Methods (organized by O)

TT 106.10: Talk

Thursday, March 19, 2015, 17:30–17:45, MA 004

Explicitly correlated self consistent field theory — •Christian Lasar and Thorsten Klüner — Carl von Ossitzky Universität, Oldenburg, Germany

There is a variety of methods available which aim to describe molecules and molecular reactions with chemical accuracy. The two main classes of these methods are density functional theory (DFT) and electron correlation approaches. DFT achieves great accuracy for many molecules and is applicable to quite large molecules. Unfortunately, DFT is not systematically improvable since the exact form of the exchange correlation functional remains unknown. Correlation methods do not suffer from this lack of systematic improvement. Unfortunately, they often require too much computational resources for large molecules. Additionally, they show a very slow convergence with the size of the basis set. Explicitly correlated methods are known to be able to solve this convergence problem. In these methods, the wavefunction is augmented with a function f_ij which explicitly depends on two electronic coordinates. Combining the advantages of low computational resources and the ability for systematic improvement, one ends up in the following ansatz for the wavefunction Ψ=(1+∑_ij f_ij) Φ, where Φ is one slater determinant. With this ansatz the long determinant expansion is avoided. Additionally, there will be a fast convergence with the basis set size. We currently investigate the derivation of the working equations and their implementation for different functions f_ij. Some results for small molecules have already been obtained and will be presented in this contribution.