Electronic Correlation in Polymers

It is well known that the Hartree-Fock method gives only an approximation to the correct total energy and wave function of a system. Unless heavy atoms are present in the system, which would require a relativistic treatment, the exact energy and wave function can be obtained only by solving the Schrodinger equation of the problem 

One should emphasize that in the case of polymers, as in the case of molecules, the HF method with a good basis set works reasonably well until one is interested only in average ground-state properties (like charge 

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More General Treatments of Electron Correlation in Polymers.—The introduction of excitonic states was just a simple example to show how one can go beyond the HF approximation to obtain correlated electron-hole pairs, whose energy level(s) may fall into the forbidden gaps in HF theory, and form the basis for interpretation of optical phenomena in semiconducting polymers. The schemes described until now for investigation of certain types of correlation effects (the DODS method for ground-state properties and the exciton-picture for excited states) are relatively simple from both the conceptual and computational points of view and they have been actually used at the ab initio level. It is evident, on the other hand, that further efforts are needed in polymer electronic structure calculations if we want to reach the level of sophistication in correlation studies on polymers which is quite general nowadays in molecular quantum mechanics. 

ABSTRACT, - After a short review of the ab initio SCF LCAO crystal orbital method the negative factor technique for the determination of the density of states in a disordered chain is presented. After this the problem of electron correlation in polymers is discussed and the generation of correlated (quasiparticle) valence and conduction bands is reviewed. 

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