Experimental estimation of molecular structure of the water-rock interface under high-temperature and high-pressure conditions revealed by in situ IR and Raman spectroscopy

In order to investigate effects of molecular behavior of interfacial water on a rock surface at high temperature and pressure conditions, a high temperature-pressure cell was developed to measure infrared (IR) and Raman spectra. As a result of IR spectroscopic measurements, a continuous shift of the OH vibration mode was obtained from ambient to hydrothermal conditions. Compared with the result of IR properties of water on a metal, IR properties of water on a quartz surface exhibit different trends: the peak position shifted to higher wavenumber with increasing temperature and slightly shifted with pressure.The IR property of water was changed by environmental conditions such as temperature, pressure and substrate.We considered a possible structure of water molecules on a quartz surface. Interfacial water molecules interacted via hydrogen bonding with surface silanol molecules of quartz. Thiswater-quartz interaction might influencewater structuring on the quartz surface.