Structures, energies, and bonding in the water heptamer

Abstract

In this paper we report the geometries and properties of 38 distinct geometrical motifs located on the B3LYP/6-31+G(d), MP2/6-311++G(d, p) potential energy surfaces of the water heptamer. Binding energies of up to 45 kcal/mol are calculated. All motifs fall within 10 kcal/mol of the most stable conformation, with at least 13 structural patterns located no more than 3 kcal/mol above, leading to a very complex potential energy surface, populated by a multitude of motifs each one allowing large numbers of conformations. Cluster stability does not seem to be correlated with the number of hydrogen bonds. Compact structures are energetically favored by electronic energies with zero-point energy corrections, while more open structures are preferred when temperature and entropy are accounted for. The molecular interactions holding the clusters as discrete units lead to large binding energies but are not strong enough to cause significant changes in the geometries of the interacting monomers. Our results indicate that bonding in the water heptamers can be considered as largely non-shared interactions with contributions from intermediate character of increasing covalency.

How Many Water Molecules Does it Take to Dissociate HCl?

“…High‐level ab initio and DFT computations on molecular clusters face a tremendous challenge in producing accurate potential energy surfaces (PESs) for intermolecular interactions owing to the exponential dependency of the number of local minima on the number of molecules . In most cases, chemical intuition is the weapon of choice to guess the best candidates.…”

An accurate and efficient computational protocol for obtaining the complete basis set limits of the binding energies of water clusters at the MP2 and CCSD(T) levels of theory: Application to (H2O)m, m = 2-6, 8, 11, 16, and 17

“…4,33,36,41,43,45, The Møller-Plesset second-order (MP2) perturbation theory has mainly been employed, but some scarce results at the Coupled Cluster Singles, Doubles, and perturbative Triples [CCSD(T)] can also be found. 45,50,56,[62][63][64]74,76 Some studies examining several series of water clusters have also appeared. 4,45,[56][57][58][59]70 Day et al studied the even-membered clusters from six to twenty water molecules by MP2 using a double-zeta basis set in 2000 and also reported CCSD(T) energies at the MP2 geometries for six hexamer isomers.…”

“…50 The binding energy of the water heptamer has been reported at both the MP2 and CCSD(T) theories. Acelas et al 76 studied five different structures at the MP2/6-311++G(d,p) and CCSD(T)/6-311++G(d,p) levels, while Kim et al 54 reported ten different isomers at MP2 with similar quality basis sets. The octamer and endecamer systems have been treated with MP2 by one of us 43 employing as large basis sets as aug-cc-pV5Z.…”

Partition potential for hydrogen bonding in formic acid dimers

“…Among the many types of intermolecular interactions, hydrogen bonding is of particular interest because hydrogen bonds (HBs) are known to be responsible for stabilization of various chemical systems, with direct implications in a wide range of scenarios, from the life‐supporting properties of liquid water to the tertiary structures of biomolecules in charge of storing and replicating genetic information . Although the very nature of hydrogen bonding is not without controversy, several types of HBs are recognized in literature .…”