Evolution of physical properties of conjugated systems

Abstract

Evolution of various physical properties of finite conjugated systems with increasing molecular size is studied using the self-consistent-charge density-functional tight-binding (SCC-DFTB) method. We usually observe a transition from the finite to the infinite regime for surprisingly short molecular chains containing only 20-30 monomer units of cis-butadiene, cyclopentadiene, pyrrole, furan, and thiophene. Such a fast convergence of equilibrium geometries, induced atomic charges, electron densities of states (DOS) and energy gaps, dipole and quadrupole moments, and polarizabilities is particularly striking considering the presence of strong pi-conjugation.