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Issue 5, 2016
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Stabilities and defect-mediated lithium-ion conduction in a ground state cubic Li3N structure

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Abstract

A stable ground state structure with cubic symmetry of Li3N (c-Li3N) is found by an ab initio initially symmetric random-generated crystal structure search method. Gibbs free energy, calculated within quasi-harmonic approximation, shows that c-Li3N is the ground state structure for a wide range of temperatures. The c-Li3N structure has a negative thermal expansion coefficient at temperatures lower than room temperature, mainly due to two transverse acoustic phonon modes. This c-Li3N phase is a semiconductor with an indirect band gap of 1.90 eV within hybrid density functional calculations. We also investigate the migration and energetics of native point defects in c-Li3N, including lithium and nitrogen vacancies, interstitials, and anti-site defects. Lithium interstitials are found to have a very low migration barrier (∼0.12 eV) and the lowest formation energy among all possible defects. The ionic conduction in c-Li3N is thus expected to occur via an interstitial mechanism, in contrast to that in the well-known α-Li3N phase which occurs via a vacancy mechanism.

Graphical abstract: Stabilities and defect-mediated lithium-ion conduction in a ground state cubic Li3N structure

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Publication details

The article was received on 12 Nov 2015, accepted on 07 Jan 2016 and first published on 07 Jan 2016


Article type: Paper
DOI: 10.1039/C5CP06946G
Author version available: Download Author version (PDF)
Citation: Phys. Chem. Chem. Phys., 2016,18, 4185-4190
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    Stabilities and defect-mediated lithium-ion conduction in a ground state cubic Li3N structure

    M. C. Nguyen, K. Hoang, C. Wang and K. Ho, Phys. Chem. Chem. Phys., 2016, 18, 4185
    DOI: 10.1039/C5CP06946G

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