Coupled-Cluster Equation of Motion Study for the Electronic and Optical Properties of Conjugated Systems

摘要

We have implemented the Coupled-Cluster Equation of Motion (CC-EOM) with single and double excitations coupled with semiempirical parameterizations, Pariser-Parr-Pople model and INDO Hamiltonians, to investigate the optical and nonlinear optical properties, electronic structures and the excited states properties for the conjugated polymers. The semiempirical parameters allow us to study the conjugated systems with extensive sizes. Firstly, by comparing with the nearly-exact Density Matrix Renormalization Group theory for the 1-d conjugated chain, we find that our CC-EOM approach can give satisfactory results for both the ground state and the excited states energies. We then present our developments to evaluate linear and nonlinear response based on the CC-EOM. We find that both the real and imaginary parts of the third-order polarizability can be solved either for static and dynamic responses. Then we apply the CC-EOM approach to study the optical signatures for the polarons in conjugated polymers. We show that there exists a correspondence between the rigidity of a polymer and its optical signature of the polarons.