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Issue 7, 2016
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Dimer-mediated cation diffusion in the stoichiometric ionic conductor Li3N

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Abstract

Non-equilibrium molecular dynamics has been used to model cation diffusion in stoichiometric Li3N over the temperature range 50 < T/K < 800. The resulting diffusion coefficients are in excellent agreement with the available experimental data. We present a detailed atomistic account of the diffusion process. Contrary to the conclusions drawn from previous studies, our calculations show that it is unnecessary to invoke the presence of a small concentration of intrinsic defects in order to initiate diffusion. The structure can be considered to consist of alternating layers of composition Li2N and Li. As the temperature increases an increasing number of cations leave the Li2N layers and migrate either to the interlayer space or to the Li layer. Those that move into the interlayer space form Li2 dimers with cations in the Li2N layers and those that move into the neighboring layer form dimers with cations therein. The two types of dimer are aligned parallel and perpendicular to [001], respectively and have lifetimes of ∼3 ps. The vacancies so created facilitate rapid diffusion in the Li2N layers and the interlayer cation motion results in slower diffusion perpendicular to the layers.

Graphical abstract: Dimer-mediated cation diffusion in the stoichiometric ionic conductor Li3N

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Supplementary files

Article information


Submitted
10 Dec 2015
Accepted
22 Jan 2016
First published
01 Feb 2016

Phys. Chem. Chem. Phys., 2016,18, 5605-5613
Article type
Paper
Author version available

Dimer-mediated cation diffusion in the stoichiometric ionic conductor Li3N

A. D. Mulliner, P. D. Battle, W. I. F. David and K. Refson, Phys. Chem. Chem. Phys., 2016, 18, 5605
DOI: 10.1039/C5CP07625K

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