Excited States

In addition to calculations on the ground state, you can also perform calculations for singly excited states, using time-dependent Hartree-Fock or density functional theory (TDHF or TDDFT)1 Keyword itddft = 1 in the gen section.. These calculations are available for a closed-shell reference wave function as spin-restricted states, or for open-shell molecules with unrestricted spin, based on an unrestricted reference. For closed-shell molecules, you can generate the restricted singlet2 Keyword rsinglet in the gen section. or restricted triplet3 Keyword rtriplet in the gen section. excited states, or both. Calculations be run in the gas phase or with the PBF solvation model. TDDFT and TDHF have been implemented in Jaguar [262] with both the full linear response4 Keyword itda = 0 in the gen section. and the Tamm-Dancoff approximation5 Keyword itda = 1 in the gen section.[30]. For a Hartree-Fock reference, the Tamm-Dancoff approximation corresponds to a configuration interaction singles (CIS) calculation.

Excited states can be calculated with the scalar ZORA or spin-orbit ZORA Hamiltonians. The scalar ZORA Hamiltonian can be used just like the nonrelativistic Hamiltonian. The spin-orbit ZORA Hamiltonian can only be used with a closed-shell reference, and the singlet and triplet exited state options are unavailable, as spin is no longer conserved. However, a closed shell system has time-reversal symmetry, and Kramers restriction replaces spin restriction. The choice of SCF spin treatment applies instead to Kramers restriction, and you must use the Restricted option for the excited state calculations.

When excited states are calculated, a spectrum file is written that contains the UV/visible spectral data, jobname_uvv.spm. This file can be read into the Spectrum Plot Panel in Maestro to generate a simulated UV/visible spectrum.