Computational Vibrational Spectroscopy of glycine in aqueous solution - Fundamental considerations towards feasible methodologies

In this work, the mid-infrared spectrum of aqueous glycine is predicted by a number of computational approaches. Velocity autocorrelation functions are applied to ab initio QMCF-MD and QM/MM-MD simulations in order to obtain IR power spectra. Furthermore, continuum solvation model augmented geometry optimizations are studied by anharmonic calculations relying on the PT2-VSCF and the VPT2 formalism. In this context, the potential based EFP hydration technique is discussed and the importance of a Monte Carlo search in conjunction with PT2-VSCF calculations is critically assessed. All results are directly compared to newly recorded experimental FT-IR spectroscopic data, elucidating the qualities of the respective methodology. Moreover, the computational approaches are discussed regarding their usefulness for the interpretation of experimental spectra. (C) 2014 Elsevier B.V. All rights reserved.