Universität zu Köln

Efthimiopoulos, Ilias ORCID: 0000-0001-6542-8188, Benson, Daryn E., Konar, Sumit ORCID: 0000-0003-3156-6536, Nylen, Johanna, Svensson, Gunnar, Haeussermann, Ulrich, Liebig, Stefan, Ruschewitz, Uwe ORCID: 0000-0002-6511-6894, Vazhenin, Grigory V., Loa, Ingo, Hanfland, Michael and Syassen, Karl (2015). Structural transformations of Li2C2 at high pressures. Phys. Rev. B, 92 (6). COLLEGE PK: AMER PHYSICAL SOC. ISSN 1550-235X

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Abstract

Structural changes of Li2C2 under pressure were studied by synchrotron x-ray diffraction in a diamond anvil cell 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 C-2 dumbbells characteristic of Immm Li2C2 are retained in Pnma Li2C2. The structure of Pnma Li2C2 relates closely to the anticotunnite-type structure. C-2 dumbbell units are coordinated by nine Li atoms, as compared to eight in the antifluorite structure of Immm Li2C2. First-principles calculations predict a transition of Pnma Li2C2 at 32 GPa to a topologically identical phase with a higher Cmcm symmetry. The coordination of C-2 dumbbell units by Li atoms is increased to 11. The structure of Cmcm Li2C2 relates closely to the Ni-2 In-type structure. It is calculated that Cmcm Li2C2 becomes metallic at pressures above 40 GPa. In experiments, however, Pnma Li2C2 is susceptible to irreversible amorphization.

Item Type:	Journal Article
Creators:	Creators Email ORCID ORCID Put Code Efthimiopoulos, Ilias UNSPECIFIED orcid.org/0000-0001-6542-8188 UNSPECIFIED Benson, Daryn E. UNSPECIFIED UNSPECIFIED UNSPECIFIED Konar, Sumit UNSPECIFIED orcid.org/0000-0003-3156-6536 UNSPECIFIED Nylen, Johanna UNSPECIFIED UNSPECIFIED UNSPECIFIED Svensson, Gunnar UNSPECIFIED UNSPECIFIED UNSPECIFIED Haeussermann, Ulrich UNSPECIFIED UNSPECIFIED UNSPECIFIED Liebig, Stefan UNSPECIFIED UNSPECIFIED UNSPECIFIED Ruschewitz, Uwe UNSPECIFIED orcid.org/0000-0002-6511-6894 UNSPECIFIED Vazhenin, Grigory V. UNSPECIFIED UNSPECIFIED UNSPECIFIED Loa, Ingo UNSPECIFIED UNSPECIFIED UNSPECIFIED Hanfland, Michael UNSPECIFIED UNSPECIFIED UNSPECIFIED Syassen, Karl UNSPECIFIED UNSPECIFIED UNSPECIFIED
URN:	urn:nbn:de:hbz:38-396302
DOI:	10.1103/PhysRevB.92.064111
Journal or Publication Title:	Phys. Rev. B
Volume:	92
Number:	6
Date:	2015
Publisher:	AMER PHYSICAL SOC
Place of Publication:	COLLEGE PK
ISSN:	1550-235X
Language:	English
Faculty:	Faculty of Mathematics and Natural Sciences
Divisions:	Faculty of Mathematics and Natural Sciences > Department of Chemistry > Institute of Inorganic Chemistry
Subjects:	no entry
Uncontrolled Keywords:	Keywords Language CRYSTAL-STRUCTURE PREDICTION; BRILLOUIN-ZONE INTEGRATIONS; AUGMENTED-WAVE METHOD; PHASE-TRANSITION; CALCIUM CARBIDES; PSEUDOPOTENTIALS; ALGORITHM; ALKALI; USPEX; CAC2 Multiple languages Materials Science, Multidisciplinary; Physics, Applied; Physics, Condensed Matter Multiple languages
Refereed:	Yes
URI:	http://kups.ub.uni-koeln.de/id/eprint/39630