First-principles electronic structure and lattice dynamics of the giant dielectric compound Na0.5Bi0.5Cu3Ti4O12
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Dosyalar
Tarih
2008
Yazarlar
Dergi Başlığı
Dergi ISSN
Cilt Başlığı
Yayıncı
IOP Publishing Ltd
Erişim Hakkı
info:eu-repo/semantics/closedAccess
Özet
We report the results of an ab initio study of electronic, dielectric, and lattice dynamical properties of high dielectric constant perovskite-derived oxide Na1/2Bi1/2Cu3Ti4O12. The calculations have been carried out within the local spin density functional approximation using norm-conserving pseudopotentials and a plane-wave basis. The ground state is found to be an antiferromagnetic direct band gap semiconductor. Lattice dynamical properties, such as Born effective charge tensors, dielectric permittivity tensors, and phonon frequencies at the Brillouin zone center were calculated using density functional perturbation theory and found to be similar to the more studied CaCu3Ti4O12 and CdCu3Ti4O12 compounds. The calculated electronic (epsilon(infinity) approximate to 11.5) and static (epsilon(0) approximate to 150) dielectric constants indicate that the observed high dielectric constant is extrinsic in origin. The main contribution to the static dielectric constant is found to be due to a low frequency (50 cm(-1)) infrared-active mode which has a large mode effective charge.
Açıklama
Anahtar Kelimeler
The Giant Dielectric Compound
Kaynak
Journal Of Physics-Condensed Matter
WoS Q Değeri
Q2
Scopus Q Değeri
Q2
Cilt
20
Sayı
17
