Structural behavior of the acetylide carbides Li2C2 and CaC2 at high pressure
2012 (English)In: Journal of Chemical Physics, ISSN 0021-9606, E-ISSN 1089-7690, Vol. 137, no 22, 224507Article in journal (Refereed) Published
The effects of high pressure (up to 30 GPa) on the structural properties of lithium and calcium carbide, Li2C2 and CaC2, were studied at room temperature by Raman spectroscopy in a diamond anvil cell. Both carbides consist of C-2 dumbbells which are coordinated by metal atoms. At standard pressure and temperature two forms of CaC2 co-exist. Monoclinic CaC2-II is not stable at pressures above 2 GPa and tetragonal CaC2-I possibly undergoes a minor structural change between 10 and 12 GPa. Orthorhombic Li2C2 transforms to a new structure type at around 15 GPa. At pressures above 18 GPa (CaC2) and 25 GPa (Li2C2) Raman spectra become featureless, and remain featureless upon decompression which suggests an irreversible amorphization of the acetylide carbides. First principles calculations were used to analyze the pressure dependence of Raman mode frequencies and structural stability of Li2C2 and CaC2. A structure model for the high pressure phase of Li2C2 was searched by applying an evolutionary algorithm.
Place, publisher, year, edition, pages
2012. Vol. 137, no 22, 224507
Research subject Materials Chemistry
IdentifiersURN: urn:nbn:se:su:diva-87137DOI: 10.1063/1.4770268ISI: 000312491400092OAI: oai:DiVA.org:su-87137DiVA: diva2:601101