Ambient-Pressure Polymerization of Carbon Anions in the High-Pressure Phase Mg2C.

Inorg Chem

Geophysical Laboratory, Carnegie Institution of Washington , Washington D.C., 20015, United States.

Published: November 2015

Experimental and theoretical methods were employed to investigate the ambient-pressure, metastable phase transition pathways for Mg2C, which was recovered after high-pressure synthesis. We demonstrate that at temperatures above 600 K isolated C(4-) anions within the Mg2C structure polymerize into longer-chain carbon polyanions, resulting in the formation of the α-Mg2C3 (Pnnm) structure, which is another local energy minimum for the carbon-magnesium system. Access to the thermodynamic ground state (decomposition into graphite) was achieved at temperatures above ∼1000 K. These results indicate that recoverable high-pressure materials can serve as useful high-energy precursors for ambient-pressure materials synthesis, and they show a novel mechanism for the formation of carbon chains from methanide structures.

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http://dx.doi.org/10.1021/acs.inorgchem.5b01780DOI Listing

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