Dynamic polarizabilities and excitation spectra from a molecular implementation of time-dependent density-functional response theory: N2 as a case study

We report the implementation of time-dependent density-functional response theory (TD-DFRT) for molecules using the time-dependent local density approximation (TDLDA). This adds exchange and correlation response terms to our previous work which used the density-functional theory (DFT) random phase approximation (RPA) M. E. Casida, C. Jamorski, F. Bohr, J. Guan, and D. R. Salahub, in Theoretical and Computational Modeling of NLO and Electronic Materials, edited by S. P. Karna and A. T. Yeates (ACS, Washington, D.C., in press), and provides the first practical, molecular DFT code capable of treating frequency-dependent response properties and electronic excitation spectra based on a formally rigorous approach. The essentials of the method are described, and results for the dynamic mean dipole polarizability and the first eight excitation energies of N2 are found to be in good agreement with experiment and with results from other ab initio methods.