Direct Atomic-Orbital Based TDHF Calculations of Frequency-Dependent Polarizabilities.

摘要

We have formulated and implemented a direct atomic integral driven method for the calculation of frequency dependent response properties at the self-consistent field (SCF) level. By avoiding the integral transformation step, as well as the storing and retrieving of atomic-orbital (ao) based integrals, we are able to use large basis sets. The practicality of the approach is illustrated and calibrated by performing a series of calculations on cyclopropenone employing up to 232 basis orbitals. We examined the scaling of the dipole polarizability with the site of the system for para-nitroaniline and its dimer. Except for a small positive enhancement of the component along the molecular axis, we find little effect of size on alpha for the system. However, if the -NN- linkage of the dimer is replaced by a -CC- linkage, thus more effectively extending the orbital conjugation by making the dimer planar, we find a large, frequency-dependent increase in the polarizability relative to twice that of the monomer (factors varying from 3 to 18, depending on frequency).