Article (Scientific journals)
First-principles study of the dielectric and dynamical properties of lithium niobate
Veithen, M.; Ghosez, Philippe
2002In Physical Review. B, Condensed Matter and Materials Physics, 65, p. 214302
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Abstract :
[en] Using a first-principles approach based on density-functional theory, the electronic, dielectric, and dynamical properties of the two phases of lithium niobate are studied. In particular, the spontaneous polarization, the optical dielectric tensors, the Born effective charges, and the zone-center phonons are computed. The Born effective charges are found to be significantly larger than the nominal ionic charges of the ions, a feature similar to what is observed in related ABO(3) compounds and attributed to the hybridization between the O 2p and Nb 4d states. The analysis of the zone-center phonons in the paraelectric phase reveals an unstable A(2u) mode to be responsible for the phase transition. The origin of the structural instability is attributed to destabilizing long-range dipolar interactions, which are not fully compensated by stabilizing short-range forces. Finally, the identification of the E modes in the ferroelectric phase, which is still the cause for debates in spite of the numerous experimental and theoretical studies, is discussed and an assignation based on the analysis of the mode-oscillator strengths and the angular dispersion relation of extraordinary phonons is proposed.
Disciplines :
Physics
Author, co-author :
Veithen, M.
Ghosez, Philippe  ;  Université de Liège - ULiège > Département de physique > Physique théorique des matériaux
Language :
English
Title :
First-principles study of the dielectric and dynamical properties of lithium niobate
Publication date :
2002
Journal title :
Physical Review. B, Condensed Matter and Materials Physics
ISSN :
1098-0121
eISSN :
1550-235X
Publisher :
American Physical Society, Woodbury, United States - New York
Volume :
65
Pages :
214302
Peer reviewed :
Peer Reviewed verified by ORBi
Available on ORBi :
since 02 December 2009

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