Revisiting small clusters of water molecules

Extensive ab initio calculations have been performed using the 6-31G(d,p) and 6-311++G(2d,2p) basis sets for several possible structures of water clusters (H 2 O) n , n ) 8-20. It is found that the most stable geometries arise from a fusion of tetrameric or pentameric rings. As a result, (H 2 O) n , n ) 8, 12, 16, and 20, are found to be cuboids, while (H 2 O) 10 and (H 2 O) 15 are fused pentameric structures. For the other water clusters (n ) 9, 11, 13, 14, and 17-19) under investigation, the most stable geometries can be thought of as arising from either the cuboid or the fused pentamers or a combination thereof. The stability of some of the clusters, namely, n ) 8-16, has also been studied using density functional theory. An attempt has been made to estimate the basis set superposition error and zero-point energy correction for such clusters at the HartreeFock (HF) level using the 6-311++G(2d,2p) basis set. To ensure that a minimum on the potential-energy surface has been located, frequency calculations have been carried out at the HF level using the 6-31G(d,p) and 6-311++G(2d,2p) basis sets for some of the clusters. Molecular electrostatic potential topography mapping has been employed for understanding the reactivity as well as the binding patterns of some of the structurally interesting clusters.

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“…Extensive ab initio calculations 16,40,53,57,67,68 62 are supportive of the cubic structure for the octamer.…”

Section: Introductionmentioning

confidence: 77%

“…1,11,[44][45][46] It is also chiral. Ab initio calculations 12,15,20,23,38,40,47,48 also predicted such a ring structure. Burke et al, 48 for example, examined various structures of pentamers at the Hartree-Fock (HF) level and found that the ring was more stable than the bipyramidal forms by at least 1 kcal/mol.…”

Section: Introductionmentioning

confidence: 84%

Structure and Stability of Water Clusters (H₂O)_n, n = 8−20: An Ab Initio Investigation

Maheshwary¹,

Patel²,

et al. 2001

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“…The cyclic global minimum of the tetramer has S 4 symmetry [66][67][68][69] and lacks the 'frustration' exhibited by the cyclic trimer and pentamer. Schütz and coworkers found no true transition states correpsonding to degenerate rearrangements in the torsional space of the tetramer [70,71].…”

Section: Water Tetramermentioning

confidence: 99%

Rearrangements and tunneling splittings of protonated water trimer

Wales¹

1999

The Journal of Chemical Physics

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Stationary points and rearrangement mechanisms are characterized for protonated water trimer using a variety of basis sets and density functional theory to describe electron correlation. For the largest basis sets there are three distinct low-lying minima separated in energy by only a few wave numbers. Ten distinct transition states were found with barriers spanning nearly three orders of magnitude. Several of these mechanisms should produce observable tunneling splittings.

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“…For the trimer, tetramer and pentamer, the lowest energy structures have been shown to be quasiplanar (2-D) monocyclic rings with each monomer acting as a singledonor and single-acceptor of hydrogen bonds. [5][6][7][8][9][10][11][12][13] Higher clusters such as heptamer 14 and octamer 15 are predicted to form 3-D noncyclic hydrogen-bonded networks at low internal temperatures by a large number of theoretical calculations. The hexamer represents a transition wherein the cyclic structures become less stable than the three-dimensional forms, which have a larger number of somewhat weaker (strained) hydrogen bonds.…”

Section: Introductionmentioning

confidence: 99%

Terahertz Laser Vibration−Rotation Tunneling Spectroscopy and Dipole Moment of a Cage Form of the Water Hexamer

1997

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Tunable terahertz laser vibration-rotation-tunneling spectroscopy has been employed to characterize the structure and hydrogen bond network rearrangement dynamics of a cage form of the water hexamer having eight hydrogen bonds. The isolated clusters are produced in a pulsed supersonic slit jet. Striking similarities are found between the structure and the average interoxygen distance R O-O (2.82 Å) of the hexamer cage and those of the basic unit of ice VI. The hybrid perpendicular band of b-and c-types is observed near 2.491 THz (83.03 cm -1 ) and rationalized to originate from the torsional motions of the two single-donor singleacceptor monomers about their donor hydrogen bonds, thereby causing changes in the dipole moments from each monomer to be orthogonal to each other as well as to be perpendicular to the approximate symmetry a-axis. Triplet spectral patterns accompanying each rovibrational transition with line spacings of 1.9 MHz and intensity ratios of 9:6:1 are attributed to the degenerate quantum tunneling that involves the exchange of protons within two similar monomers of the cluster. The Stark effect of the degenerate asymmetry doublets of K a g 3 has been analyzed to yield vibration-and (J,K a )-dependent electric dipole moment components ranging from 1.82 to 2.07 D along the a-axis of this near prolate rotor. The selection rules establish that this dipole moment component preserves the sign upon vibrational excitation. A reasonable agreement is found between the dipole measurement and the results of a model calculation using an iterated induction expansion including the quadrupole-induced dipole. The same model has also been applied to extract the individual monomer dipole moments for the dimer and the cage and cyclic hexamers. The trends of two molecular propertiessthe contraction of the R O-O distance and enhancement of the average individual monomer dipole with increasing cluster size up to the cyclic hexamer-are found to converge exponentially to the bulk phase values. In both cases, the cage properties deviate from the trends established by the dimer and cyclic clusters.

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Revisiting small clusters of water molecules

Cited by 309 publications

References 21 publications

Structure and Stability of Water Clusters (H₂O)_n, n = 8−20: An Ab Initio Investigation

Structure and Stability of Water Clusters (H₂O)_n, n = 8−20: An Ab Initio Investigation

Rearrangements and tunneling splittings of protonated water trimer

Terahertz Laser Vibration−Rotation Tunneling Spectroscopy and Dipole Moment of a Cage Form of the Water Hexamer

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Revisiting small clusters of water molecules

Cited by 309 publications

References 21 publications

Structure and Stability of Water Clusters (H2O)n, n = 8−20: An Ab Initio Investigation

Structure and Stability of Water Clusters (H2O)n, n = 8−20: An Ab Initio Investigation

Rearrangements and tunneling splittings of protonated water trimer

Terahertz Laser Vibration−Rotation Tunneling Spectroscopy and Dipole Moment of a Cage Form of the Water Hexamer

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Structure and Stability of Water Clusters (H₂O)_n, n = 8−20: An Ab Initio Investigation

Structure and Stability of Water Clusters (H₂O)_n, n = 8−20: An Ab Initio Investigation