High temperature decomposition of polymeric carbon monoxide at pressures up to 120 GPa

Year: 2023

Authors: Scelta D., Ceppatelli M., Bini R., Pakhomova A., Garbarino G., Mezouar M., Santoro M.

Autors Affiliation: European Lab Nonlinear Spect, LENS, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Florence, Italy; CNR, Ist Chim Composti OrganoMetall, Consiglio Nazl Ric, ICCOM, Via Madonna Piano 10, I-50019 Sesto Fiorentino, Florence, Italy; Univ Firenze, Dipartimento Chim Ugo Schiff, Via Lastruccia 3, I-50019 Sesto Fiorentino, Florence, Italy; European Synchrotron Radiat Facil, ESRF, 71 Ave Martyrs,CS40220, F-38043 Grenoble 9, France; CNR, Consiglio Nazl Ric, Ist Nazl Ott, INO, Via Nello Carrara 1, I-50019 Sesto Fiorentino, Florence, Italy.

Abstract: While polymeric carbon monoxide (pCO) has been experimentally found to remain amorphous and undecomposed at room temperature up to 50 GPa, the question of whether crystalline counterparts of it can be obtained naturally raises. From different computational studies, it can be inferred that either the crystallization of amorphous pCO (a-pCO) or its decomposition into a mixture of CxOy suboxides (x > y) or carbon and CO2 may occur. In this study, we report experimental investigations of the high temperature (700-4000 K) transformation of a-pCO in the 47-120 GPa pressure range, conducted by x-ray diffraction in laser heated diamond anvil cells. Our results show the formation of no crystalline phases other than CO2 phase V, thus indicating the decomposition of the pristine a-pCO into CO2 and, likely, a mixture of amorphous CxOy suboxides and amorphous carbon hardly detectable at extreme conditions. These results support the theoretical picture of the pCO decomposition. We also show that the pressure-temperature kinetic border for this decomposition is very steep, thus indicating a strongly pressure-dependent kinetic barrier.

Journal/Review: JOURNAL OF CHEMICAL PHYSICS

Volume: 159 (8)      Pages from: 84501-1  to: 84501-6

More Information: We thank the European Laboratory for Nonlinear Spectroscopy (LENS) for hosting part of the research, the Fondazione Cassa di Risparmio di Firenze for the support through the grant SALUS, and the ESRF synchrotron for providing access to the ID27 beamline and for financial support under Proposal No. CH-6151. We thank Irina Sniguirev for her support with the gold coating of the gaskets. M.C. would like to acknowledg e the projects HP-PHOTOCHEM (Fondazione Cassa di Risparmio di Firenze) and GreenPhos-alta pressione (CNR).
KeyWords: Phase transitions, Diamond anvil cells, Synchrotron radiation, Crystalline solids, Annealing, Carbon monoxide, X-ray diffraction
DOI: 10.1063/5.0157907