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MM: Fachverband Metall- und Materialphysik

MM 46: Interfaces

MM 46.7: Vortrag

Donnerstag, 28. Februar 2008, 18:00–18:15, H 0111

Gaussian Polarizable Model for Metal Oxides — •Fawzi Mohamed and Joachim Sauer — Humboldt University

We present the first results of a polarizable force field geared toward metal oxides which is well suited for QM:MM embedding.

The model uses atom centered gaussians s and p functions to describe the long range electrostatic part.

The s function charge is assumed to be constant (no charge transfer allowed) and the p functions depend on the field and the local environment around each atom.

The optimal values for the s and p functions, the values that the potential tries to fit, are obtained from the electronic density ρ of DFT calculations minimizing

E=(ρ−ρ|ρ−ρ)=

∫

(ρ(r)−ρ(r))(ρ(r′)−ρ(r′))

|r−r′|

dr dr′ (1)

as is done in RI methods, but only to reproduce the long range part of it. This is achieved by replacing the 1/|r−r′| operator with

C(r,r″)F(r″)C(r″,r) (2)

where C is half coulomb operator

|r−r′|

∫

C(r,r″)C(r″,r′)dr″ (3)

and F is a filter that removes the core region of the atoms.

Fitting these optimal values gives an implicitly interacting polarizable model that reproduces well the long range electrostatic field.

Then the short range part of the forcefield is optimized with force matching against DFT results.