Winslow Professor of Chemistry George Shields and Co-Director of the Center for Molecular Design Karl Kirschner recently published a paper in Synthesis and Reactivity in Inorganic, Metal-Organic, and Nano-Metal Chemistry. Their article, "The Limitations of Certain Density Functionals in Modeling Neutral Water Clusters," was published in a special issue of the journal devoted to water clusters.

Professors Shields and Kirschner have used density functional theory (DFT) with four different functionals and with basis sets optimized for studying water clusters to calculate the structures and energies for selected water dimer, trimer, tetramer, pentamer, hexamer, and octamer structures. They compared the results to the CBS-APNO and G3 model chemistry methods, and with highly accurate MP2 complete basis set limit energies. They found that while all the DFT methods capture the minimum energy structures for tetramers and pentamers, and reproduce the interaction energies well, they fail to find certain structures where London dispersion forces are critical to the interaction. Specifically structures that are not composed of cyclic rings, such as the tetramer pyramid and the pentamer cage structures, are not minima on the DFT potential energy hypersurfaces. This work is essential for the senior thesis work of Marco Allodi and Greg Hartt, who are studying aerosol formation in the atmosphere.