Pressure induced phase transitions in hydroquinone.
ABSTRACT High pressure behavior of alpha-hydroquinone (1,4-dihydroxybenzene) has been studied using Raman spectroscopy up to pressures of 19 GPa. Evolution of Raman spectra suggests two transitions around 3.3 and 12.0 GPa. The first transition appears to be associated with the lowering of crystal symmetry. Above 12.0 GPa, Raman bands in the internal modes region exhibit continuous broadening suggesting that the system is progressively evolving into a disordered state. This disorder is understood as arising due to distortion of the hydrogen-bonded cage across the second transition around 12 GPa.
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ABSTRACT: The structure of a new methane hydrate has been solved at 3 GPa from neutron and x-ray powder diffraction data. It is a dihydrate in which a 3D H-bonded network of water molecules forms channels surrounding the methane molecules. The network is closely related to that of ice-Ih and the methane-water system appears to be the first in which a cage clathrate hydrate is transformed into an ice-related hydrate (a "filled ice").Physical Review Letters 12/2001; 87(21):215501. · 7.94 Impact Factor
- Physical review. B, Condensed matter 06/1995; 51(17):11262-11269.
Article: Hydrogen bonding in water.[show abstract] [hide abstract]
ABSTRACT: Computer simulations using density functional theory based ab initio path integral molecular dynamics have been carried out to investigate hydrogen bonding in water under ambient conditions. Structural predictions for both H2O and D2O, which include the effects of zero-point energy, thermal motion, and many body polarization effects, are contrasted with classical simulations that ignore nuclear quantum effects. The calculated effect of H/D isotope substitution on the water structure is much smaller than the difference between the classical and quantum path integral results, and is in excellent agreement with the measured H/D difference data from both neutron and x-ray scattering.Physical Review Letters 12/2003; 91(21):215503. · 7.94 Impact Factor