Dynamical atomic charges: The case of compounds

Ph Ghosez, J. Michenaud, X. Gonze

Research output: Contribution to journalArticlepeer-review

458 Citations (Scopus)

Abstract

Based on recent first-principles computations in perovskite compounds, especially (Formula presented) we examine the significance of the Born effective charge concept and contrast it with other atomic charge definitions, either static (Mulliken, Bader, etc.) or dynamical (Callen, Szigeti, etc.). It is shown that static and dynamical charges are not driven by the same underlying parameters. A unified treatment of dynamical charges in periodic solids and large clusters is proposed. The origin of the difference between static and dynamical charges is discussed in terms of local polarizability and delocalized transfers of charge: local models succeed in reproducing anomalous effective charges thanks to large atomic polarizabilities but, in (Formula presented) compounds, ab initio calculations favor the physical picture based upon transfer of charges. Various results concerning barium and strontium titanates are presented. The origin of anomalous Born effective charges is discussed thanks to a band-by-band decomposition which allows us to identify the displacement of the Wannier center of separated bands induced by an atomic displacement. The sensitivity of the Born effective charges to microscopic and macroscopic strains is examined. Finally, we estimate the spontaneous polarization in the four phases of barium titanate.

Original languageEnglish
Pages (from-to)6224-6240
Number of pages17
JournalPhysical Review B - Condensed Matter and Materials Physics
Volume58
Issue number10
DOIs
Publication statusPublished - 1998
Externally publishedYes

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