Density-matrix renormalization group studies of metal-halogen chains within a two-band extended Peierls-Hubbard model

Anusooya, Y and Pati, Swapan K and Ramasesha, S (1999) Density-matrix renormalization group studies of metal-halogen chains within a two-band extended Peierls-Hubbard model. In: Journal Of Physics-Condensed Matter, 11 (11). pp. 2395-2412.

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Abstract

The phase diagram of halogen-bridged mixed-valence metal complexes (MX) has been studied using a two-band extended Peierls-Hubbard model employing the recently developed density-matrix renormalization group method. We present the energies, charge- and spin-density distributions, bond orders, and charge-charge and spin-spin correlations, for the ground state, for different parameters of the model. The effects of bond alternation and site-diagonal distortion on the ground-state properties are considered in detail. We observe that the site-diagonal distortion plays a significant role in deciding the nature of the ground state of the system. We find that while the charge-density-wave (CDW) and bond-order-wave (BOW) phases can coexist, the CDW and SDW (spin-density-wave) phases are mutually exclusive in most cases. We have also studied the doped MX chains both with and without bond alternation and site-diagonal distortion in the CDW as well as SDW regimes. We find that the additional charges in the polarons and bipolarons for hole doping are confined to a few sites, in the presence of bond alternation and site-diagonal distortion. For electron doping, we find that the additional charge(s) is (are) smeared over the entire chain length, and although the energetics implies a disproportionation of the negatively charged bipolaron, the charge- and spin-density distributions do not reflect this. A positively charged bipolaron disproportionates into two polarons in the SDW region. There is also bond-order evidence for compression of the bond length for the positively charged polaronic and bipolaronic systems and an elongation of the bonds for systems with negatively charged polarons and bipolarons.

Item Type:	Journal Article
Publication:	Journal Of Physics-Condensed Matter
Publisher:	IOP Publishing
Additional Information:	Copyright of this article belongs to IOP Publishing.
Department/Centre:	Division of Chemical Sciences > Solid State & Structural Chemistry Unit
Date Deposited:	06 Mar 2009 07:24
Last Modified:	19 Sep 2010 05:01
URI:	http://eprints.iisc.ac.in/id/eprint/18319

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