%0 Journal Article %1 hlwoodcock:Meuwly2002a %A Meuwly, M. %A Karplus, M. %D 2002 %J JOURNAL OF CHEMICAL PHYSICS %K bibtex-import %N 6 %P 2572--2585 %T Simulation of proton transfer along ammonia wires: An äb initio" and semiempirical density functional comparison of potentials and classical molecular dynamics %V 116 %X Protonated ammonia clusters of the composition (NxH3x+1)(+) with x=2,3,4 are investigated by using the gradient corrected, three-parameter functional by Becke based on the functional by Lee, Yang, and Parr (B3LYP/6-31G(**)) and self-consistent charges density functional tight-binding (SCC-DFTB) methods for calculating the potential energy surface and forces in the Born-Oppenheimer approximation. They are used for classical molecular dynamics simulations at temperatures ranging from 5 K to 600 K. Results from the two methods are compared for proton transfer in N2H7+. The number of proton transfer events as a function of temperature is similar, although at low temperatures, SCC-DFTB cuts off more rapidly than B3LYP/6-31G(**). Calculated vibrational spectra agree well for the intermolecular N-N and intramolecular N-H stretch excitations. Both approaches lead to broad, relatively unstructured bands extending over about 1500 cm(-1) for the proton transfer coordinate. Simulations at the SCC-DFTB/MD level for larger (NxH3x+1)(+) (xless than or equal to4) clusters are presented and discussed. They show significant structural reorganization within the cluster. Consecutive proton hops within a few tenths of a fs are observed. A N2H7+ cluster immersed in a water shell containing 25 water molecules was studied by the mixed quantum mechanical/molecular mechanics (QM/MM) method with SCC-DFTB for the QM part. The presence of water appears to impede proton transfer. Including corrections for basis set superposition error in the MP2/aug-cc-pVTZ and B3LYP/6-31G(**) calculations has a small effect. It increases the barrier heights from 0.78 kcal/mol to 1.28 kcal/mol (MP2) and from 0.10 kcal/mol to 0.27 kcal/mol (B3LYP), respectively. (C) 2002 American Institute of Physics.

@article{hlwoodcock:Meuwly2002a, abstract = {Protonated ammonia clusters of the composition (NxH3x+1)(+) with x=2,3,4 are investigated by using the gradient corrected, three-parameter functional by Becke based on the functional by Lee, Yang, and Parr (B3LYP/6-31G(**)) and self-consistent charges density functional tight-binding (SCC-DFTB) methods for calculating the potential energy surface and forces in the Born-Oppenheimer approximation. They are used for classical molecular dynamics simulations at temperatures ranging from 5 K to 600 K. Results from the two methods are compared for proton transfer in N2H7+. The number of proton transfer events as a function of temperature is similar, although at low temperatures, SCC-DFTB cuts off more rapidly than B3LYP/6-31G(**). Calculated vibrational spectra agree well for the intermolecular N-N and intramolecular N-H stretch excitations. Both approaches lead to broad, relatively unstructured bands extending over about 1500 cm(-1) for the proton transfer coordinate. Simulations at the SCC-DFTB/MD level for larger (NxH3x+1)(+) (xless than or equal to4) clusters are presented and discussed. They show significant structural reorganization within the cluster. Consecutive proton hops within a few tenths of a fs are observed. A N2H7+ cluster immersed in a water shell containing 25 water molecules was studied by the mixed quantum mechanical/molecular mechanics (QM/MM) method with SCC-DFTB for the QM part. The presence of water appears to impede proton transfer. Including corrections for basis set superposition error in the MP2/aug-cc-pVTZ and B3LYP/6-31G(**) calculations has a small effect. It increases the barrier heights from 0.78 kcal/mol to 1.28 kcal/mol (MP2) and from 0.10 kcal/mol to 0.27 kcal/mol (B3LYP), respectively. (C) 2002 American Institute of Physics.}, added-at = {2006-06-16T05:03:46.000+0200}, author = {Meuwly, M. and Karplus, M.}, biburl = {https://www.bibsonomy.org/bibtex/22892367d25d2235c84d5eb3bc9808bb6/hlwoodcock}, citeulike-article-id = {569895}, interhash = {fe01e592114668b82015559461dbe7c6}, intrahash = {2892367d25d2235c84d5eb3bc9808bb6}, journal = {JOURNAL OF CHEMICAL PHYSICS}, keywords = {bibtex-import}, number = 6, pages = {2572--2585}, priority = {2}, timestamp = {2006-06-16T05:03:46.000+0200}, title = {Simulation of proton transfer along ammonia wires: An "ab initio" and semiempirical density functional comparison of potentials and classical molecular dynamics}, volume = 116, year = 2002 }