A density functional theory study of the hydrogen bond interactions in glycine dimers

We report a theoretical study on the stability and bonding of glycine dimers using diverse DFT functionals (B3LYP, B3PW91, mPW1PW91, and MPW1B95) and MP2 calculations. It comprises the determination of the optimized structures, relative stabilities, corrected binding energies, and vibrational spectra of four different dimers, whose electron densities are analyzed using the Quantum Theory of Atoms in Molecules. DFT functionals show the cyclic planar dimer with two 0-H center dot center dot center dot 0 hydrogen bonds as the most stable and the most strongly bound structure. They find the stacked dimer between 1.7 and 4.7 kcal/mol higher, whereas it is the most stable with MP2. (C) 2007 Elsevier B.V. All rights reserved.