Comparison of static and dynamic methods of treatment of anharmonicity for the vibrational study of isolated and aqueous forms of guanine

This theoretical study provides the anharmonic vibrational wavenumbers of isolated and aqueous guanine. They were performed at the DFT B3LYP/6-31+G(d,p) level of theory using two different ways for the treatment of anharmonicity: time-independent (VPT2) and time-dependent (molecular dynamics) approaches. The wavenumbers obtained are compared to experimental data for isolated and aqueous forms: the VPT2 approach is slightly better than MD, especially for the determination of stretching and wagging (NH) motions. Finally, the structural model of solvatation used for aqueous guanine which combines an explicit solvent model with a polarizable continuum model (PCM) was validated.