ФТТ, 2004, том 46, выпуск 9

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Cluster ab initio modeling of local lattice instability in relaxor ferroelectrics

O.E.Kvyatkovskii *,**, F.Karadag *, A.Mamedov *, G.A.Zakharov ***

* Cukurova University, Adana, Turkey
** A.F. Ioffe Physico-Technical Institute, Russian Academy of Sciences,
194021 St. Petersburg, Russia
*** St. Petersburg State Polytechnic University,
195220 St. Petersburg, Russia
E-mail: Kvyatkovskii@mail.ioffe.ru

(Received 29 december 2003)

The possibility of a zigzag type instability occurring for oxygen atoms in B-O-B, B-O-Nb, Nb-O-Nb linear chains is examined in disordered mixed perovskite compounds Pb(B1/3,Nb2/3)O3 (B=Mg, Zn, Cd). Local adiabatic potentials for oxygen atoms are studied using total energy calculations by ab initio Hartree--Fock + MP2 method for many-atomic clusters with different oxygen surroundings of lead atoms. The effect of lattice relaxation along the chain on a shape of the local potential in the transverse direction for the central oxygen atom is considered.

Supported by the TUBITAK (NATO PC Advanced Fellowship Program), by Russian Foundation for Basic Research (Projects N 01-02-17801 and 03-02-17557) and by Program of the Branch of Physical Sciences of Russian Academy of Sciences.

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