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MM: Fachverband Metall- und Materialphysik

MM 7: Computational Materials Modelling II

MM 7.1: Talk

Monday, March 14, 2011, 14:30–14:45, IFW B

Alkane Adsorption in Chabazite - Different Ways to Model Van Der Waals Interactions — •Florian Göltl and Jürgen Hafner — Faculty for Physics, University of Vienna, Austria

In this work we investigate the performance of different levels of theory to describe the adsorption of alkanes in chabazite, a mineral from the zeolite family. Modeling this problem is an especially challenging task, since, even though there is a very weak bond between the adsorption site (in our case an H- or Na- atom) and the alkane, the bonding is dominated by van der Waals (vdW) interactions between the alkane and the zeolite wall.

Even though vdW-interactions are not included in standard density functional theory (DFT), several ways to include them in DFT and post-DFT methods were proposed. In this work we compare the performance of (i) DFT in its generalized gradient approximation after Perdew, Burke and Ernzerhof (PBE), (ii) PBE with an added forcefield after Grimme (PBE-d), (iii) the van der Waals density functional after Dion et al. (vdW-DF), (iv) the Adiabatic Connection Fluctuation Dissipation Theorem in its Random Phase Approximation (RPA), (v) a modified form of the RPA, where the Hartree Fock exchange-contribution is evaluated selfconsistently (RPA-HF) and (vi) 2nd order Møller Plesset perturbation theory (MP2).

We give a critical discussion of differences in structural parameters, charge distribution and energetics and propose an improved way to compare the theoretically obtained results with experiment.