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Title: Stabilities and defect-mediated lithium-ion conduction in a ground state cubic Li3 N structure

A stable ground state structure with cubic symmetry of Li3N (c-Li3N) is found by 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 temperature. The c-Li3N structure has a negative thermal expansion coefficient at temperatures lower than room temperature, due mainly 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 calculation. 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. Thus, the ionic conduction in c-Li3N is expected to occur via an interstitial mechanism, in contrast to that in the well-known α-Li3N phase which occurs via a vacancy mechanism.
Authors:
 [1] ;  [2] ;  [3] ;  [3]
  1. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronomy
  2. North Dakota State Univ., Fargo, ND (United States). Center for Computationally Assisted Science and Technology
  3. Ames Lab. and Iowa State Univ., Ames, IA (United States). Dept. of Physics and Astronom
Publication Date:
OSTI Identifier:
1249339
Report Number(s):
IS-J--8948
Journal ID: ISSN 1463-9076; PPCPFQ
Grant/Contract Number:
AC02-07CH11358; SC0001717
Type:
Accepted Manuscript
Journal Name:
Physical Chemistry Chemical Physics. PCCP (Print)
Additional Journal Information:
Journal Name: Physical Chemistry Chemical Physics. PCCP (Print); Journal Volume: 18; Journal Issue: 5; Journal ID: ISSN 1463-9076
Publisher:
Royal Society of Chemistry
Research Org:
Ames Laboratory (AMES), Ames, IA (United States)
Sponsoring Org:
USDOE Office of Science (SC), Basic Energy Sciences (BES) (SC-22)
Country of Publication:
United States
Language:
English
Subject:
37 INORGANIC, ORGANIC, PHYSICAL, AND ANALYTICAL CHEMISTRY