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Electron correlation effects on the mechanical and optical properties of polymers
Author(s) -
Suhai S.
Publication year - 1984
Publication title -
international journal of quantum chemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.484
H-Index - 105
eISSN - 1097-461X
pISSN - 0020-7608
DOI - 10.1002/qua.560260819
Subject(s) - electronic correlation , perturbation theory (quantum mechanics) , exciton , polaron , chemistry , electron , quasiparticle , atomic physics , wave function , condensed matter physics , molecular physics , physics , materials science , quantum mechanics , superconductivity
Møller‐Plesset perturbation theory has been applied to investigate the influence of electron correlation on the mechanical and optical properties of infinite periodic polyethylene (PE) and on the optical properties of polydiacetylenes (PDAs). The microscopic Young's modulus and deviations from Hooke's law have been calculated for PE using both restricted and unrestricted Hartree–Fock (RHF, UHF) zeroth‐order wave functions. These deviations become really important in the region of 30–40% elongation ϵ and they lead to a maximum of the retractive force of f = 0.814 mdyn at ϵ = 0.38 and of f = 0.631 mdyn at ϵ = 0.31 in the case of RHF and UHF reference functions, respectively. The best theoretical value of the longitudinal elastic modulus of PE (comparing different atomic basis function sets) is 334 GPa at the HF level and 276 GPa including electron correlation. The charge transfer exciton spectrum of PE and of PDA models has been calculated with the help of a Green's‐function approach using quasiparticle states of the electron polaron method. The first singlet excitations occur at 8.67 eV in PE and at 1.7–2.1 eV in PDAs, in good agreement with experiments.