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Phys. Rev. B 45, 6435–6458 (1992)

Two-band model for halogen-bridged mixed-valence transition-metal complexes. II. Electron-electron correlations and quantum phonons

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S. M. Weber-Milbrodt
Physikalisches Institut, Universität Bayreuth, W-8580 Bayreuth, Federal Republic of Germany

J. Tinka Gammel
Physikalisches Institut, Universität Bayreuth, W-8580 Bayreuth, Federal Republic of Germany
Centers for Materials Science and Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545

A. R. Bishop
Centers for Materials Science and Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545

E. Y. Loh, Jr.
Centers for Materials Science and Nonlinear Studies and Theoretical Division, Los Alamos National Laboratory, Los Alamos, New Mexico 87545
Thinking Machines Corporation, 245 First Street, Cambridge, Massachusetts 02142-1214

Received 23 May 1991; published in the issue dated 15 March 1992

We study the effects of electron-electron interactions in halogen-bridged mixed-valence transition-metal linear-chain complexes (MX chains) applying a simple 3/4-filled two-band discrete tight-binding (extended) Peierls-Hubbard model with both on-site and intersite electron-phonon couplings. We employ a variety of methods: perturbation theory, Hartree-Fock approximation, and exact diagonalization in the limit of classical adiabatic phonons, and a variational approach allowing for a finite phonon frequency, i.e., quantum phonons and isotope effect. This variety of methods has proved necessary to obtain a complete picture, due to the structural richness of this model. We investigate the competition between the electron-electron and electron-phonon interactions in a wide range of parameter regimes for both ground and excited states. We focus on values relevant to the MX chains, probing the experimental variation as X and M are varied among X=Cl, Br, and I and M=Pt, Pd, and Ni (spanning electron-phonon-interaction-dominated to electron-electron-interaction-dominated materials).

© 1992 The American Physical Society

URL:
http://link.aps.org/doi/10.1103/PhysRevB.45.6435
DOI:
10.1103/PhysRevB.45.6435
PACS:
71.38.+i, 78.50.-w, 71.45.Lr, 78.30.-j

See Also

See Also: J. Tinka Gammel, A. Saxena, I. Batistić, A. R. Bishop, and S. R. Phillpot, Two-band model for halogen-bridged mixed-valence transition-metal complexes. I. Ground state and excitation spectrum, Phys. Rev. B 45, 6408 (1992).

 
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