A direct algorithm for self-consistent-field linear response theory and application to C60: Excitation energies, oscillator strengths, and frequency-dependent polarizabilities

We present a direct self-consistent-field (SCF)-type algorithm and its implementation for the computation of linear response properties: excitation energies, oscillator strengths, and frequency-dependent polarizabilities within the time-dependent SCF or random phase approximation. The treatment of singles configuration interaction for electronic excitations and Hartree–Fock instability criteria are covered as special cases. The algorithm is based on proven direct SCF methodology. This, together with full exploitation of molecular symmetry, opens the way to the treatment of large molecules. Applications to C60 strongly support the assignment of the lowest-lying dipole allowed transition to the strong band at 3.8 eV.