Pople's Gaussian‐3 model chemistry applied to an investigation of (H₂O)₈ water clusters

Abstract

ABSTRACT:The Gaussian-3 method developed by Pople and coworkers has been used to calculate the free energy of neutral octamer clusters of water, (H 2 O) 8 . The most energetically stable structures are in excellent agreement with those determined from experiment and those predicted from previous high-level calculations. Cubic structures are favored over noncubic structures over all temperature ranges studied. The D 2d cubic structure is the lowest free energy structure and dominates the potential energy and free energy hypersurfaces from 0 K to 298 K.

Atmospheric Implications for Formation of Clusters of Ammonium and 1−10 Water Molecules

“…Each structure was run through a geometry optimization using Gaussian 0319 at the MP2/6-31G* level. Test calculations included in supplemental information shows MP2/6-31G* to be both accurate and relatively efficient, in agreement with previous results on water clusters 20,21. The frequencies from optimized structures were scaled by 0.9646 and used to obtain entropies and free energies 22.…”

“…It is somewhat surprising that MP2/6-31G* scaled frequencies are as good as anharmonic MP2 frequencies with the Dunning basis sets, yet we have shown this is true for water clusters. 33 This is no doubt why our previous calculations of water clusters based on MP2/6-31G* are better than those using the G3 method,34 which is based on scaled HF/-31G* frequencies 5,20,21,25,32,33. Calculations on sulfur are more problematic however, and MP2/6-31G* cannot be trusted for CS 2 (H 2 O) n clusters 35.…”

A Hirshfeld partitioning of polarizabilities of water clusters

“…[1][2][3][4][5][6][7][8][9] The structure of the water clusters, based on hydrogen bonds, forms a link between single water molecules and bulk water. [1][2][3][4][5][6][7][8][9] The structure of the water clusters, based on hydrogen bonds, forms a link between single water molecules and bulk water.…”

CCSD(T), W1, and other model chemistry predictions for gas‐phase deprotonation reactions

“…The G3 and CBS‐APNO methods model the geometries and energies of hydrogen‐bonded water and ion‐water clusters quite accurately 41–48, and this deprotonation study adds to the body of evidence that shows the reliability of these two model chemistries. Furthermore, the W1 method, which is computationally more expensive, is also highly accurate.…”