Structural transformations of Li2C2 at high pressures
2015 (English)In: Physical Review B. Condensed Matter and Materials Physics, ISSN 1098-0121, E-ISSN 1550-235X, Vol. 92, no 6, 064111Article in journal (Refereed) Published
Structural changes of Li2C2 under pressure were studied by synchrotron x-ray diffraction in a diamond anvilcell under hydrostatic conditions and by using evolutionary search methodology for crystal structure prediction.We show that the high-pressure polymorph of Li2C2, which forms from the Immm ground-state structure (Z = 2)at around 15 GPa, adopts an orthorhombic Pnma structure with Z = 4. Acetylide C2 dumbbells characteristic ofImmm Li2C2 are retained in Pnma Li2C2. The structure of Pnma Li2C2 relates closely to the anticotunnite-typestructure. C2 dumbbell units are coordinated by nine Li atoms, as compared to eight in the antifluorite structureof Immm Li2C2. First-principles calculations predict a transition of Pnma Li2C2 at 32 GPa to a topologicallyidentical phase with a higher Cmcm symmetry. The coordination of C2 dumbbell units by Li atoms is increasedto 11. The structure of Cmcm Li2C2 relates closely to the Ni2 In-type structure. It is calculated that Cmcm Li2C2becomes metallic at pressures above 40 GPa. In experiments, however, Pnma Li2C2 is susceptible to irreversibleamorphization.
Place, publisher, year, edition, pages
2015. Vol. 92, no 6, 064111
Research subject Materials Chemistry
IdentifiersURN: urn:nbn:se:su:diva-120033DOI: 10.1103/PhysRevB.92.064111ISI: 000359858800001OAI: oai:DiVA.org:su-120033DiVA: diva2:850164