Pressure-Induced Phase Transition in Crystalline DCOOD by Raman Scattering in the Diamond Cell

Abstract

The Raman spectra of crystalline deuterated formic acid (DCOOD) in a diamond anvil cell have been measured at pressures up to 100 kbar and 300 K. The frequency of the stretching O–D mode near 2000 cm⁻¹ decreases strongly with increasing pressure, which is due to the increasing strength of the deuterium bonds in the zig-zag chain. The pressure-induced phase transition at about 45 kbar has been found on the characteristic high-pressure behavior of the stretching O–D, the stretching C=O, and the bending C–D modes, which is discussed by focusing on the cis-trans conformational change associated with the deuteron transfer.