Rearrangements and tunneling splittings of protonated water dimer

Wales, David J.

doi:10.1063/1.478972

Cited by 45 publications

(40 citation statements)

References 58 publications

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“…In a later study [50], performed at considerably higher spectral resolution, more evidence for a very floppy molecule was found. The number of observed rovibrational lines was considerably more than one would expect for a rigid molecule and was speculatively attributed to tunneling splittings caused by large amplitude motion [51].…”

Section: Methodsmentioning

confidence: 92%

Gas Phase Vibrational Spectroscopy of Strong Hydrogen Bonds

Asmis

Neumark

Bowman

2006

Hydrogen‐Transfer Reactions

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The hydrogen bond interaction is key to understanding the structure and properties of water, biomolecules, self-assembled nanostructures and molecular crystals. However, much confusion remains about its electronic nature, a combination of van der Waals, electrostatic and covalent contributions, leading to a wide variety of hydrogen bonds with bond strengths ranging from 2 to 40 kcal mol -1 . In particular, our understanding of strong, low-barrier hydrogen bonds and their central role in enzyme catalysis [1], biomolecular recognition [2], proton transfer across biomembranes [3] and proton transport in aqueous media [4] remains incomplete. The central aim of this chapter is to outline some recent advances in the research on strongly hydrogen bonded model systems in the gas phase with emphasis on the work from our research groups.Strong hydrogen bonds (A_H_B) are often classified based on their hydrogen bond energy; a typically cited lower limit is >15 kcal mol -1 [5]. Their most prominent physical properties are large NMR downfield chemical shifts and considerably red-shifted hydrogen stretch frequencies. Moreover, the H-atom transfer barrier, a characteristic feature of weak hydrogen bonds A-H_B, is either absent or very small in these systems (at their minimum energy geometry). Consequently, the H-atom in homoconjugated (A = B) strong hydrogen bonds is equally shared by the two heavy atoms forming two identical strong hydrogen bonds. This symmetry is lost in heteroconjugated (A " B) systems, but the H-atom remains in a more centered position, i.e., the distance between the heavy atoms is smaller than in weaker hydrogen bonded systems. Strong hydrogen bonds can either be lowbarrier, as in (HO_H_OH) -, or single-well, as in (Br_H_I) -, depending on the form of the potential curve along the H-atom exchange coordinate (see Fig. 3.1 and below).Hydrogen bonds are very sensitive to perturbation, due to an intimate interdependence between the heavy atom separation, the H-atom exchange barrier and the position of the light H-atom leading to unusually high proton polarizabilities. Therefore it can prove advantageous to study strong hydrogen bonds in the gas Hydrogen-Transfer Reactions. Edited by

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Section: Methodsmentioning

confidence: 92%

Gas Phase Vibrational Spectroscopy of Strong Hydrogen Bonds

Asmis

Neumark

Bowman

2006

Hydrogen‐Transfer Reactions

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“…This state alone absorbs light only very weakly (see Fig. 1), but the state arising from the combination of w 3 and the water-water stretching (550 cm The fact that the H 5 O + 2 cation may interconvert between several low energy barriers connecting equivalent minima had already been pointed out by Wales [29], who showed that the correct symmetry group, because wagging and internal rotation motions are allowed, is the permutation-inversion group G 16 [33]. Our study shows that the symmetry analysis in G 16 is necessary to understand some important features of the IR linear absorption spectrum.…”

Section: Discussionmentioning

confidence: 99%

“…If the internal rotation motion around α is assumed to be unfeasible, the symmetry analysis can be performed using the D 2d point group. The permutation-inversion group G 16 contains the D 2d point group as a subgroup, but allows additionally to permute the two hydrogens of one of the water monomers [28,29]. The …”

Section: Table I Around Herementioning

confidence: 99%

Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water dimer. II. Infrared spectrum and vibrational dynamics

Vendrell¹,

Gatti²,

Meyer³

2007

The Journal of Chemical Physics

224

295

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“…The G 16 point group allows, however, exchange of both hydrogen atoms in the same water molecule, i.e., allows rotation of the water monomers with respect to each other. 2,33 This motion is accounted for by the ␣ coordinate, which describes the full rotation of one monomer around the central axis and so spans the range ͓0,2͒. In previous studies it was shown that the rotation around ␣ generates a tunneling splitting of the ground vibrational state of about 1 cm −1 .…”

Section: Kinetic Energy Operator For H 5 O 2 + : Mixed Jacobi/valmentioning

confidence: 99%

Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water-dimer III: Mixed Jacobi-valence parametrization and benchmark results for the zero point energy, vibrationally excited states, and infrared spectrum

Vendrell

Brill

Gatti

et al. 2009

The Journal of Chemical Physics

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Quantum dynamical calculations are reported for the zero point energy, several low-lying vibrational states, and the infrared spectrum of the H(5)O(2)(+) cation. The calculations are performed by the multiconfiguration time-dependent Hartree (MCTDH) method. A new vector parametrization based on a mixed Jacobi-valence description of the system is presented. With this parametrization the potential energy surface coupling is reduced with respect to a full Jacobi description, providing a better convergence of the n-mode representation of the potential. However, new coupling terms appear in the kinetic energy operator. These terms are derived and discussed. A mode-combination scheme based on six combined coordinates is used, and the representation of the 15-dimensional potential in terms of a six-combined mode cluster expansion including up to some 7-dimensional grids is discussed. A statistical analysis of the accuracy of the n-mode representation of the potential at all orders is performed. Benchmark, fully converged results are reported for the zero point energy, which lie within the statistical uncertainty of the reference diffusion Monte Carlo result for this system. Some low-lying vibrationally excited eigenstates are computed by block improved relaxation, illustrating the applicability of the approach to large systems. Benchmark calculations of the linear infrared spectrum are provided, and convergence with increasing size of the time-dependent basis and as a function of the order of the n-mode representation is studied. The calculations presented here make use of recent developments in the parallel version of the MCTDH code, which are briefly discussed. We also show that the infrared spectrum can be computed, to a very good approximation, within D(2d) symmetry, instead of the G(16) symmetry used before, in which the complete rotation of one water molecule with respect to the other is allowed, thus simplifying the dynamical problem.

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Rearrangements and tunneling splittings of protonated water dimer

Cited by 45 publications

References 58 publications

Gas Phase Vibrational Spectroscopy of Strong Hydrogen Bonds

Gas Phase Vibrational Spectroscopy of Strong Hydrogen Bonds

Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water dimer. II. Infrared spectrum and vibrational dynamics

Full dimensional (15-dimensional) quantum-dynamical simulation of the protonated water-dimer III: Mixed Jacobi-valence parametrization and benchmark results for the zero point energy, vibrationally excited states, and infrared spectrum

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