Hydrogen bond dynamics and vibrational spectral diffusion in aqueous solution of formaldehyde: a first principles molecular dynamics study

Water spectacle extraordinary ability to form a variety of hydrogen bonded structure when confronted with hydrophilic solutes. We present the comparative analysis of structural and dynamical features of deuterated formaldehyde in heavy water (D2O) using density functional theory (DFT) and dispersion corrected DFT. Ab initio molecular dynamics calculation is performed by Car-Parrinello method and frequency-time calculations using time series analysis method at ambient conditions. We find that the higher frequency of OD modes of water present inside the first solvation shell of formaldehyde is a result of weak interaction compared to bulk water. We also find that the inclusion of dispersion (i.e., BLYP-D) alters the dynamical features like diffusion, frequency correlation with enhancement of momentum; therefore, molecules experience lower barrier toward their motion and show relatively faster dynamics.