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Advances in Physical Chemistry
Volume 2011 (2011), Article ID 868610, 11 pages
http://dx.doi.org/10.1155/2011/868610
Research Article

Exchange Perturbation Theory for Multiatomic Electron System and Its Application to Spin Arrangement in Manganite Chains

1Theoretical Physics Department, St. Petersburg State Polytechnic University, 29 Polytechnicheskaya, St. Petersburg 195251, Russia
2Solid State Electronic Sector, Ioffe Physical Technical Institute, 26 Polytechnicheskaya, St. Petersburg 194021, Russia

Received 19 September 2010; Revised 21 December 2010; Accepted 14 February 2011

Academic Editor: Lowell D. Kispert

Copyright © 2011 E. V. Orlenko et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

A new methodology of binding energy calculation with respect to different spin arrangements for a multiatomic electron system is developed from the first principle in the frame of the exchange perturbation theory (EPT). We developed EPT formalism in the general form of the Rayleigh-Srchödinger expansion with a symmetric Hamiltonian, taking into account an exchange and nonadditive contributions of a superexchange interaction. The expressions of all corrections to the energy and wave function were reduced to the nonsymmetric Hamiltonian form. The EPT method is extended for the case of degeneracy in the total spin of a system. As an example of the application of the developed EPT formalism for the degeneracy case, spin arrangements were considered for the key M n –O– M n ( M n : Mn3+ or Mn4+) fragments in manganites. In M n –O– M n for La1/3Ca2/3MnO3 are in good agreement the obtained estimations of Heisenberg parameter and binding energy with the available experimental data.