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Pressure-induced superconductivity in CaC2
KTH, School of Industrial Engineering and Management (ITM), Materials Science and Engineering.
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2013 (English)In: Proceedings of the National Academy of Sciences of the United States of America, ISSN 0027-8424, E-ISSN 1091-6490, Vol. 110, no 23, 9289-9294 p.Article in journal (Refereed) Published
Abstract [en]

Carbon can exist as isolated dumbbell, 1D chain, 2D plane, and 3D network in carbon solids or carbon-based compounds, which attributes to its rich chemical binding way, including sp-, sp(2)-, and sp(3)-hybridized bonds. sp(2)-hybridizing carbon always captures special attention due to its unique physical and chemical property. Here, using an evolutionary algorithm in conjunction with ab initio method, we found that, under compression, dumbbell carbon in CaC2 can be polymerized first into 1D chain and then into ribbon and further into 2D graphite sheet at higher pressure. The C2/m structure transforms into an orthorhombic Cmcm phase at 0.5 GPa, followed by another orthorhombic Immm phase, which is stabilized in a wide pressure range of 15.2-105.8 GPa and then forced into MgB2-type phase with wide range stability up to at least 1 TPa. Strong electron-phonon coupling. in compressed CaC2 is found, in particular for Immm phase, which has the highest lambda value (0.562-0.564) among them, leading to its high superconducting critical temperature T-c (7.9 similar to 9.8 K), which is comparable with the 11.5 K value of CaC6. Our results show that calcium not only can stabilize carbon sp(2) hybridization at a larger range of pressure but also can contribute in superconducting behavior, which would further ignite experimental and theoretical interest in alkaline-earth metal carbides to uncover their peculiar physical properties under extreme conditions.

Place, publisher, year, edition, pages
National Academy of Sciences , 2013. Vol. 110, no 23, 9289-9294 p.
Keyword [en]
high pressure, metallization
National Category
Engineering and Technology
URN: urn:nbn:se:kth:diva-124979DOI: 10.1073/pnas.1307384110ISI: 000320503000033ScopusID: 2-s2.0-84878701183OAI: diva2:638971
Swedish Research Council

QC 20130805

Available from: 2013-08-05 Created: 2013-08-02 Last updated: 2013-08-05Bibliographically approved

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