Regensburg 2004 – wissenschaftliches Programm
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SYLS: Life Sciences on the Nanometer Scale - Physics Meets Biology
SYLS 3: Symposium "Life Sciences on the Nanometer Scale - Physics Meets Biology"
SYLS 3.20: Poster
Mittwoch, 10. März 2004, 16:00–18:30, B
Quantum Monte Carlo study of small molecules and hydrogen bonded model systems - benchmarking density functionals — •M. Fuchs1, A. Badinski1, J. Ireta1, P. Kratzer1, C. Filippi2 und M. Scheffler1 — 1Fritz-Haber-Institut der MPG, Berlin — 2Instituut Lorentz, Univ. Leiden
Diffusion Monte Carlo (DMC) calculations can be useful to validate (and correct) results from density-functional theory (DFT) where many-electron correlations must be approximated. DMC is not yet a routine tool however, partly because experience to corroborate its robustness is still scarce. Here we apply the pseudopotential fixed-node DMC method to (i) selected small molecules and (ii) model systems for hydrogen bonds, the latter playing a key role for the structure and functionality of, e.g., biomolecules. We carefully monitor how DMC performs dependent on (nonlocal) pseudopotentials and on the optimization of the initial trial wavefunction. We find that both aspects can be nontrivial, even for the simple N2 diatomic. For finite formamide chains our DMC data show that the cooperative increase of the H-bond strength in longer chains is best reproduced in DFT using the PBE gradient corrected functional. Our findings support a recent DFT study of the stabilization of α helical polyalanine which found an unusually large cooperativity of the H-bonds [J. Ireta et al., J. Phys. Chem. B 107, 1432 (2003)].