Prediction of a high-pressure phase transition and other properties of solid CO/sub 2/ at low temperatures

Journal Article · Thu Sep 15 00:00:00 EDT 1988 · Phys. Rev. B: Condens. Matter; (United States)

DOI:https://doi.org/10.1103/PhysRevB.38.6265· OSTI ID:6844175

Kuchta, B; Etters, R D

An optimization procedure is used to minimize the Gibbs free energy of solid CO/sub 2/ at pressures 0less than or equal toPless than or equal to16 GPa, with respect to the unit-cell parameters, center-of-mass coordinates, and orientations of all the independent molecules. A lattice-dynamics procedure is used to calculate the libron frequencies. The observed Pa3 structure is predicted at low pressures, and a transition to an orthorhombic Cmca phase is found at P = 4.3 GPa, with a volume change ..delta..V = 0.3 cm/sup 3//mole. The calculated second virial coefficients, sublimation energy, molar volume, pressure-volume relation, and libron frequencies in the Pa3 phase are in good agreement with experiment. In the Cmca phase the calculated libron frequencies agree fairly well with recent Raman scattering results. An analysis of the potential-energy surface shows that the large observed hysteresis associated with the transition may be the result of large barriers between the phases.

• Research Organization: Physics Department, Colorado State University, Fort Collins, Colorado 80523
• OSTI ID: 6844175
• Journal Information: Phys. Rev. B: Condens. Matter; (United States), Vol. 38:9
• Country of Publication: United States
• Language: English

Related Subjects

36 MATERIALS SCIENCE
CARBON DIOXIDE
CRYSTAL-PHASE TRANSFORMATIONS
CRYSTAL STRUCTURE
FREE ENTHALPY
HYSTERESIS
POTENTIAL ENERGY
PRESSURE DEPENDENCE
SOLIDS
VERY HIGH PRESSURE
CARBON COMPOUNDS
CARBON OXIDES
CHALCOGENIDES
ENERGY
OXIDES
OXYGEN COMPOUNDS
PHASE TRANSFORMATIONS
PHYSICAL PROPERTIES
THERMODYNAMIC PROPERTIES
360602* - Other Materials- Structure & Phase Studies