A two level approach to predict minimum energy structures of higher hydrated clusters of oxalic acid

摘要

A simple strategy is presented to study large sized molecular clusters taking hydrated clusters of dibasic oxalic acid, (COOH)(2)center dot nH(2)O, n = 9-12 as a case study. Prediction of minimum energy structures is carried out first applying Atom Centered Density Matrix Propagation (ADMP) molecular dynamic simulations. The low energy conformers thus obtained are considered as input for further optimization applying DFT based electronic structure theory with suitable DFT functional to generate more accurate structures. This approach does not allow missing any low energy structure of large sized hydrated clusters. It is observed that even in presence of twelve water molecules only one of the carboxylic protons of oxalic acid molecule is transferred to solvent water molecule. The other carboxylic proton is retained by the acid molecule.