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Water Dimer (water + dimer)

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Chemistry100%

Selected Abstracts

Proton collisions with the water dimer at keV energies

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2009
O. Quinet
Abstract Proton collisions with the water dimer are studied using a nonadiabatic, direct, time-dependent approach called electron nuclear dynamics (END). Fragmentation of the water dimer in collisions with protons at energies of 5.0, 1.0 keV and 200 eV is the primary aim of this initial study of water clusters using END. We report on the initial fragmentation dynamic, that is, for times less than 200 fs. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source]

Explicitly correlated SCF study of anharmonic vibrations in (H2O)2

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2002
Donald D. Shillady
Abstract Modeling solvation in high-pressure liquid chromatography (HPLC) requires calculation of anharmonic vibrational frequencies of solvent clusters for a statistical partition function. An efficient computational method that includes electron correlation is highly desirable for large clusters. A modified version of the "soft Coulomb hole" method of Chakravorty and Clementi has recently been implemented in a Gaussian-lobe-orbital (GLO) program (PCLOBE) to include explicit electron,electron correlation in molecules. The soft Coulomb hole is based on a modified form of Coulomb's law: An algorithm has been developed to obtain the parameter "w" from a polynomial in the effective scaling of each primitive Gaussian orbital relative to the best single Gaussian of the H1s orbital. This method yields over 90% of the correlation energy for molecules of low symmetry for which the original formula of Chakravorty and Clementi does not apply. In this work, all the vibrations of the water dimer are treated anharmonically. A quartic perturbation of the harmonic vibrational modes is constrained to be equal to the exact Morse potential eigenvalue based on a three-point fit. This work evaluates the usefulness of fitting a Morse potential to a hydrogen bond vibrational mode and finds it to be slightly better than using MP2 vibrational analysis for this important dimer. A three-point estimate of the depth, De, of a Morse potential leads to a correction formula for anharmonicity in terms of the perturbed harmonic frequency: When scaled by 0.9141, the harmonic Morse method leads to essentially the same results as scaling the BPW91 local density method by 0.9827. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source]

A new approach to counterpoise correction to BSSE

JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 11 2006
Annia Galano
Abstract In the present work the intermolecular BSSE, associated to the A,B interaction, is obtained by subtracting the intramolecular BSSE of the fragments from the intramolecular BSSE of the supermolecule, and considering every atom as a fragment in the calculation of each intramolecular BSSE. This atom by atom scheme (CPaa) is based on the consideration that the proximity of the fragments may affect the intramolecular BSSE of every involved species, and artificially influences the value of the BSSE associated to the supermolecule formation. It drastically decreases the reported counterpoise overcorrection of the A,B interaction, even though it does not deal with all the overcorrection because it includes all the orbitals, and not only the unoccupied ones. This new approach has been tested on the water dimer, some hydrogen fluoride weakly bonded complexes, the conformational analysis of 1,2-dichloroethane, and the reaction profile of formaldehyde + OH reaction. © 2006 Wiley Periodicals, Inc. J Comput Chem 27: 1203,1210, 2006 [source]

Electron Donation in the Water,Water Hydrogen Bond

CHEMISTRY - A EUROPEAN JOURNAL, Issue 4 2009
Rustam
Donation is not from an sp3orbital: Decomposition analysis, based on absolutely localized molecular orbitals, provides an alternative and somewhat unconventional view of hydrogen bonding in the water dimer. A new description of the electron-donating orbital is uncovered:,unlike sp3 lone pairs, a single donor,acceptor orbital pair forms, in which the donating orbital changes its orientation according to the relative positions of the two molecules. [source]

Probing the Vibrations of Shared, OH+O-Bound Protons in the Gas Phase

CHEMPHYSCHEM, Issue 5 2004
David T. Moore Dr.
Spectral signature of a proton bridge? Gas-phase infrared spectra are reported in the range of 500,1800 cm,1 for three species with short, strong hydrogen bonds, namely the proton-bound dimers of dimethyl ether (shown in the picture) and diethyl ether, and protonated 1,1,-oxybis[2-methoxyethane] (diglyme). The spectra are all quite similar, and furthermore they also strongly resemble the spectrum of the proton-bound water dimer (H5O2+), suggesting that there may be a conserved "spectral signature" for a proton bound between two oxygen atoms. [source]