Dresden 2003 – wissenschaftliches Programm
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SYCN: Computational nanoscience - from materials to biology
SYCN 102: Computational Nanoscience: From Materials to Biology (Poster, gemeinsam mit SYSE)
SYCN 102.9: Poster
Dienstag, 25. März 2003, 19:00–21:00, ZEU/160
Hydrogen bonded systems: A comparative DFT study — •L. Ismer, J. Ireta, and J Neugebauer — Faradayweg 4-6, D-14195 Berlin
As Hydrogen bonds (hb) and proton transfer (pt) play a key role for the functionality of biomolecules, they have to be described accurately to adequately simulate such systems. We therefore performed a comparative DFT study on various hydrogen bonded benchmark systems by determining hb strengths, pt barriers, atomic geometries and vibrational frequencies, using i) the PBE-functional and, stimulated by recent reports, ii) the PBE-LDA-functional (exchange from PBE, correlation from LDA). We find that PBE gives accurate hb strengths (error 1 kcal/mol) but underestimates pt barriers by 5 kcal/mol. Although this error is reflected in the geometries and vibrations, the deviations for the zero-point corrections are generally rather small ( 0.5 kcal/mol). For PBE-LDA we found improved pt barriers (error 2 kcal/mol), vibrations and geometries but hb strengths are underestimated by 2 kcal/mol. Based on this approach we calculated the vibrations and the free energy of an inifinite polyalanine a-helix and compared our results with experiment.