Study of excited states of polyethylene in the Hartree–Fock, Tamm–Dancoff, and random‐phase approximations

摘要: We report calculations of the excitonic spectra all‐trans polyethylene in Hartree–Fock, Tamm–Dancoff, and random‐phase approximations. For formulation approximations beyond Hartree–Fock level, we have used particle–hole propagator technique. In first case interaction between excited electron hole is neglected latter two cases it taken into account at order electron–electron interaction. Using 3–21G atomic basis set, elementary gap reduced from about 17 eV level to 13 Tamm–Dancoff approximation. The both are also different. difference results obtained very small. discuss densities exciton states for different quasi momenta (K=0 or K=π/a), band interactions spins.