Berlin 2015 – scientific programme
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O: Fachverband Oberflächenphysik
O 19: Frontiers of Electronic Structure Theory: Many-Body Effects on the Nano-Scale I
O 19.8: Talk
Tuesday, March 17, 2015, 12:30–12:45, MA 004
Polynomial-oriented linear least squares fits of potential energy surfaces for quantum dynamics — •Florian Habecker and Thorsten Klüner — Universität Oldenburg, Germany
The field TD-QM Molecular Dynamics is facing two major problems within the BO-approximation: I. Solution of the TISE for the electrons and II. Solution of the TDSE for the nuclei. Electronic structure calculations result in a K-dimensional PES (K: number of d.f. for the nuclei) on which the motion of the nuclei is simulated, subsequently.
For economical reasons, the number of sampling points calculated by QC methods is generally smaller than those needed in the QD calculation. Hence, an interface is required to link the two major tasks. Taking the scalar energies E with the corresponding geometry parameters as input, the output of such an interface is a function to calculate any points of the PES, i.e. interpolated and extrapolated values.
Following classical papers on H3+ [1 and refs. therein], the linear model function was chosen as a K-dimensional polynomial in this study. The lack of flexibility in this uniform ansatz was restored using appropriate non-linear variable transformations. Applying the method of LLS, precise fits can be calculated in a single non-iterative step. The capability of this approach was validated with a set of 7942 ab initio data points from a 3-D PES of a CO/Ti9O18Mg714+-system [2]. Precise fits with chemical accuracy and better have been obtained for moderate expansions of the model function.
[1] W. Meyer, P. Botschwina, P. Burton, J. Chem. Phys. 84, 891 (1986).
[2] H. Spieker, T. Klüner, Phys. Chem. Chem. Phys. 16, 18743 (2014).