The structures and energies of water clusters have been widely used to benchmark the performances of various electronic structure models. We now predict structures and energies for water clusters containing up to 100 waters, including in many instances multiple isomers, with tight binding density functional theory (DFTB). With currently available parameters, we find DFTB structures to be of very high quality, while a simple additive hydrogen bond correction term must be added in order to correct for a systematic error in the predicted cluster energies. The resulting hydrogen-bond corrected tight binding density functional model is a practical method for the calculation of very large water cluster structures and energies. We compare our DFTB results to other density functional theory (DFT) calculations as well as previously reported high-level wave-function theory calculations. Our energies are in very good agreement with the available reference data; a root-mean-square difference of 0.6 kcal/mol is obtained.

From water clusters to nanodrops: A tight-binding density functional study

243rd National Meeting (2012)

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