Berlin 2005 – wissenschaftliches Programm
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AKB: Biologische Physik
AKB 200: Poster Session II
AKB 200.4: Poster
Dienstag, 8. März 2005, 17:00–19:00, Poster TU C
Hydrogen bonding vs. stacking interactions in DNA base pairs - a Diffusion Monte Carlo study — •M. Fuchs1, C. Filippi2, J. Ireta1, L. Ismer1, and M. Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin — 2Instituut Lorentz, Univ. Leiden (NL)
Diffusion Monte Carlo (DMC) calculations can provide accurate total energies of molecular systems. DMC is thus useful for benchmarking (computationally cheaper) calculations based on density functional theory where one is relying on approximations for the exchange-correlation functional. On the other hand DMC remains computationally feasible even for larger systems where conventional correlated approaches such as Configuration Interaction or Coupled Cluster are at present too demanding. Here we explore DMC to study hydrogen bonded and stacked conformations of adenine-thymine and methylated adenine-thymine. Our results for the intermolecular interaction energies show that DMC predicts both hydrogen bond strengths and stacking interactions in agreement with results from the Coupled Cluster [CCSD(T)] approach, confirming these where they differ from MP2 data. We further show that gradient corrected density functionals (GGA-DFT) can yield reasonable bond strengths of the hydrogen bonded complexes but fail to bind the stacked conformations. Adding empirical corrections for the missing dispersion (van der Waals) attraction in GGA-DFT [1] we find that the stacked conformations do bind, yet markedly too strongly when compared to our DMC results. [1] Q. Wu and W. Yang, J. Chem. Phys. 116, 515 (2002).