Constraints on the phase diagram of nonmolecular CO2 imposed by infrared spectroscopy
Year: 2009
Authors: Santoro M., Gorelli FA.
Autors Affiliation: European Lab Non Linear Spect, I-50019 Florence, Italy; Univ Roma La Sapienza, Res Ctr, SOFT INFM CNR, I-00185 Rome, Italy.
Abstract: The investigation of the high-pressure phase diagram of CO2, specifically in the nonmolecular forms, is a challenging experimental issue, due to the large metastability of this material. Here we report on the determination of the pressure threshold for forming nonmolecular CO2 from the molecular crystal, in the P-T range of 10-53 GPa and 296-715 K, respectively. The study is based on a large set of IR spectroscopy measurements, which allows to detect, with a high sensitivity, the onset of the formation of nonmolecular, amorphous carbonia. This metastable form is first formed in the attempts to obtain nonmolecular, crystalline CO2, upon increasing pressure, for kinetic reasons. Therefore, it is identified an upper pressure bound for the real-phase boundary between the molecular solid and the nonmolecular, thermodynamically stable crystal, which results to be remarkably lower than those detected by other techniques. Also, it is shown how the hysteresis of the molecular-to-nonmolecular transformation is reduced upon increasing the temperature. The study adds constraints on the high-pressure, thermodynamic phase diagram of nonmolecular CO2.
Journal/Review: PHYSICAL REVIEW B
Volume: 80 (18) Pages from: 184109-1 to: 184109-5
More Information: This work was supported by the European Community under Contract No. RII3-CT2003-506350, and by the Ente Cassa di Risparmio di Firenze, through the grant Firenze Hydrolab.KeyWords: carbon compounds; high-pressure solid-state phase transformations; infrared spectra; metastable states; phase diagrams; thermal stabilityDOI: 10.1103/PhysRevB.80.184109Citations: 14data from “WEB OF SCIENCE” (of Thomson Reuters) are update at: 2024-10-20References taken from IsiWeb of Knowledge: (subscribers only)