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Issue 43, 2012
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High pressure structures of “111” type iron-based superconductors predicted from first-principles

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Abstract

The high-pressure crystal structures of the “111” type iron-based superconductors: NaFeAs, LiFeP and LiFeAs have been systematically explored by using particle-swarm structural searches. It was found that though these iron-based superconductors are chemically similar, they adopted distinct structural phase transitions: P4/nmmCmcmP[3 with combining macron]m1 for NaFeAs, P4/nmmCmcmI4mm for LiFeP, and P4/nmmP[3 with combining macron]m1 → I4mmP63/mmc for LiFeAs under high pressure. The high pressure orthorhombic Cmcm phase preserved the structural features of FeX4(X = As, P) tetrahedral layers present in the ambient-pressure P4/nmm structure. However, the FeX4 tetrahedrons in the Cmcm phase were clearly distorted, leading to changes in the electronic behavior around the Fermi level. Under higher pressures, the FeX4 layered structural features were no longer persistent and three-dimensional crystal structures were stabilized in other P[3 with combining macron]m1, I4mm, and P63/mmc phases, which featured FeAs5/FeAs6 hexahedron and octahedrons, FeX5 tetragonal pyramids, and FeAs6 octahedrons, respectively. Analysis of the electronic density of states suggests that most of the high pressure phases are metallic except for the tetragonal I4mm phase, which possesses a narrow band gap. This semiconducting state might relate to the tetragonal pyramid structure formed by FeX5 unit, which might be favorable for charge localization.

Graphical abstract: High pressure structures of “111” type iron-based superconductors predicted from first-principles

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Publication details

The article was received on 06 Aug 2012, accepted on 10 Sep 2012 and first published on 10 Sep 2012


Article type: Paper
DOI: 10.1039/C2CP42734F
Citation: Phys. Chem. Chem. Phys., 2012,14, 15029-15035
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    High pressure structures of “111” type iron-based superconductors predicted from first-principles

    X. Zhang, Y. Wang and Y. Ma, Phys. Chem. Chem. Phys., 2012, 14, 15029
    DOI: 10.1039/C2CP42734F

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