ISSN:
0020-7608
Keywords:
Computational Chemistry and Molecular Modeling
;
Atomic, Molecular and Optical Physics
Source:
Wiley InterScience Backfile Collection 1832-2000
Topics:
Chemistry and Pharmacology
Notes:
The importance of many-body interactions beyond the mean-field approximation of the Hartree-Fock (HF) self-consistent-field crystal orbital formalism is analyzed in one-dimensional (lD) transition-metal (3d) polymers with extended organic π ligands. The correlation energies are expressed in a quasiparticle picture. They are divided into long-range contributions that are coordinated with the basis of spatially uncorrelated Bloch orbitals and into short-range correlations derived for local rearrangement processes that are described in terms of a one-electron basis which breaks the translational symmetry of the lD system. Both contributions (long-range and short-range correlations) are fragmented into elements of physical significance (hole and electron self-energies for the former interactions; relaxation, pair-relaxation and pairremoval terms for the local virtual excitations). The magnitude of these elements is analyzed as a function of the characters of the one-electron states in the HF bands, the occupation patterns at the 3d centers, the available particle and hole channels in the elementary fluctuations and the energies and shapes of the various bands. The broad spectrum of possible amplifications and compensations leading to the quasiparticle shifts in metallomacrocycles is discussed. The different mechanisms to change the dispersions and to modify the width of the ∊(k) curves are studied. It is shown that electron correlation and relaxation in transition-metal polymers can lead even to a broadening of the energy bands. This behavior is in contrast to the influence of many-body effects in simpler homogeneous materials where electron correlation is in any case accompanied by a narrowing of the dispersions (i.e., detraction of the group velocities of particles and holes). Possible modifications in the shapes of the one-particle curves and the quasiparticle bands are also considered in the text [transition from a “normal ∊(k) dispersion” to an energy band with a negative slope as a result of electron correlation]. Simplified formulas are derived that allow for a rough assessment of the various correction terms even in structurally complicated transition-metal stacks with extended organic ligands. The approximate relations are used to correct the HF band structures of complex onedimensional metallomacrocycles as well as simpler crystalline materials by means of the quasiparticle approximation.
Additional Material:
17 Ill.
Type of Medium:
Electronic Resource
URL:
http://dx.doi.org/10.1002/qua.560270309
