8.1 Functionalities of ESCF and EGRAD

escf and egrad are designed as efficient tools for response and excited state calculations on large molecules. escf serves to compute the following properties for HF and KS reference states:

Spin-restricted closed-shell and spin-unrestricted ground states (except for stability analysis) are supported. The RI-J approximation in conjunction with LDA, GGA, and meta-GGA (MGGA) functionals is implemented for all properties. Excitation energies and transition moments can be computed either within the full time-dependent HF (TDHF) or time-dependent DFT (TDDFT) formalisms or within the Tamm-Dancoff approximation (TDA).

Furthermore, two-component relativistic Kramers-restricted closed-shell ground states are supported (vertical electronic excitation energies as well as transition moments, oscillator and rotatory strengths). LDA and GGA functionals are implemented in combination with the RI-J approximation.

Excited state first order properties can be evaluated analytically using egrad. They include:

Moreover, analytical gradients of static and frequency-dependent polarizabilities are available from egrad. Together with vibrational normal modes from the aoforce or Numforce they are used to calculate vibrational Raman intensities. Excited state gradients for MGGA functionals are presently unavailable.

Again, ground states may be spin-restricted closed-shell or spin-unrestricted, RI-J is available, and either full TDDFT/TDHF or the TDA can be used. For further details we refer to a recent review [101].