Regensburg 2013 – scientific programme
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O: Fachverband Oberflächenphysik
O 35: Poster Session I (Metal, semiconductor and oxide substrates: structure and adsorbates; Graphene)
O 35.54: Poster
Tuesday, March 12, 2013, 18:15–21:45, Poster B1
DFT+D Van-der-Waals C6 coefficients for ionic crystals — •Steffen Seiler and Bernd Meyer — Interdisziplinäres Zentrum für Molekulare Materialien und Computer-Chemie-Centrum, Universität Erlangen-Nürnberg
Previous studies have shown that Grimme’s dispersion correction to
DFT [1] leads to an overestimation of the binding energy of molecules
on ionic surfaces. The reason is that in the Grimme D2 scheme no
distinction is made between Van-der-Waals C6 coefficients for
neutral and charged species of the same element, although they clearly
possess different polarizabilities.
We propose a simple scheme for adjusting the C6 coefficients of the
cations in ionic crystals which is based on the static polarizability.
Thin films are exposed to an external electric field and the film
polarizability is determined by linear regression of the induced dipole
moment.
The method has been applied to magnesium oxide and hydroxide and we obtained
very similar C6 values for the Mg cations as recently proposed by the
Grimme group based on TDDFT calculations [2].
To demonstrate the impact of the modified Van-der-Waals correction, calculated
binding curves for the interaction of different small molecules (CH4,
H2O and SiMe(OH)3) with magnesium oxide and hydroxide model clusters
will be shown and the results will be compared to MP2 benchmark calculations.
[1] S. Grimme, J. Comp. Chem. 27, 1787 (2006).
[2] S. Ehrlich et al.,Chem. Phys. Chem. 12, 3414 (2011).