Ambient-Pressure Polymerization of Carbon Anions in the High-Pressure Phase Mg2C.
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.
Geophysical Laboratory, Carnegie Institution of Washington , Washington D.C., 20015, United States.
Stevce
S
Stefanoski
Department of Physics and Engineering Physics, University of Saskatchewan , Saskatoon, Saskatchewan S7N 5E2, Canada.
Hanyu
H
Liu
Department of Physics and Engineering Physics, University of Saskatchewan , Saskatoon, Saskatchewan S7N 5E2, Canada.|Canadian Light Source , Saskatoon, Saskatchewan S7N 2V3, Canada.
Yansun
Y
Yao
Geophysical Laboratory, Carnegie Institution of Washington , Washington D.C., 20015, United States.
Timothy A
TA
Strobel