Münster 1999 – scientific programme
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CP: Chemische Physik
CP 20: Große Moleküle und Aggregate
CP 20.4: Talk
Wednesday, March 24, 1999, 17:00–17:15, Phy
An approximate DFT method for large biological molecules — •Marcus Elstner1,2, Sandor Suhai2, and Thomas Frauenheim1 — 1Universität-GH Paderderborn, Fachbereich Physik, Theoretische Physik, D - 33098 Paderborn — 2German Cancer Research Center, Department of Molecular Biophysics, D-69120 Heidelberg
A new method for electronic structure calculations of large molecular systems is presented. This generalized self-consistent charge tight-binding (SCC-TB) methodology can be derived from a second-order expansion of the Kohn-Sham energy functional with respect to density fluctuations at a given reference density (Elstner et al., PRB 58 (1988) 7260). All integrals are calculated at the reference density in a two-center approximation in advance, therefore, the time limiting step during geometry optimizations and MD runs is the diagonalization of the Hamiltonmatrix. To benchmark our method for reaction energies, geometries and vibrational frequencies on a large set of small organic molecules we compare to other semi empirical (AM1, PM3), ab initio methods and experimental values. We calculated H-bond energies for a large set of hydrogen bonded compounds and DNA base-pairs. We present also results for DNA base-pair stacking energies. The method also gives a reliable description of the energetics and structure of small polypeptides. We calculated relative energies of various conformers of polyalanine up to 20 residues and studied the helix formation in polypeptides. The critical sequence lenght for the formation of an α-helix, the coexistence of two helix types and their relative stabilities are discussed.