期刊
JOURNAL OF PHYSICS AND CHEMISTRY OF SOLIDS
卷 68, 期 7, 页码 1336-1340出版社
PERGAMON-ELSEVIER SCIENCE LTD
DOI: 10.1016/j.jpcs.2007.02.035
关键词
optical materials; defects
First-principles plane-wave ultrasoft pseudopotential method within local density approach (LDA) has been used to study three possible vacancy-defect models for non-stoichiometric lithium niobate (LiNbO3): (1) the oxygen-vacancy model V-O(2+) + 2V(Li)(-), (2) the niobium-vacancy model 5Nb(Li)(4+) + 4V(Nb)(5-), and (3) the lithium-vacancy model 4V(Li)(-) + Nb-Li(4+). The corresponding formation energies are obtained via energy minimization of a supercell. In Nb-rich environment, the calculated defect formation energies, both under oxidation and reduction conditions, show little effect on the intrinsic defect structures. We find that the lithium vacancy model 4V(Li)(-) + Nb-Li(4+) has the most stable configuration in the non-stoichiometric lithium niobate crystals. Our calculations also show that the formation of any type of neutral defects and Frenkel pairs in a Nb-rich environment is difficult. (c) 2007 Elsevier Ltd. All rights reserved.
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