Vibrational spectrum of condensed H2O in hydrogen-bonding environment: an ab initio simulation study

Abstract

Local hydrogen-bonding environments have important influences on the intra-molecular O–H stretchings of H2O molecules. The relationship between the contributions of intra-molecular O–H stretching and the local hydrogen-bonding environments is investigated using ab initio simulation for a condensed H2O system at 300 K, 1.7 g/cm3, and calculated/estimated pressure of approximately 9 GPa. The calculation results demonstrate that the local hydrogen-bonding environments around the two intra-molecular hydrogen atoms are not always similar. The existence of asymmetric local hydrogen environments will result in decoupling of the intra-molecular O–H stretchings in the molecule; thus, the broad O–H stretching band may be decomposed into a sum that includes isolated intra-molecular O–H stretchings but not symmetric stretching and asymmetric stretching. This research serves as a reminder to pay attention to the influence of an asymmetric local hydrogen-bonding environment on the vibrational details of the H2O molecular system and will facilitate the interpretation of measurements of the infrared and Raman spectra of the condensed H2O systems.