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# 7.11.11 Frozen-Density Embedding: FDE-ADC methods

(February 4, 2022)

FDE-ADC923 is a method to include interactions between an embedded species and its environment into an ADC($n$) calculation based on Frozen Density Embedding Theory (FDET).1200, 1201 FDE-ADC supports ADC and CVS-ADC methods of orders 2s,2x and 3 and regular ADC job control keywords also apply.

The FDE-ADC method starts with generating an embedding potential using a MP($n$) density for the embedded system (A) and a DFT or HF density for the environment (B). A Hartree-Fock calculation is then carried out during which the embedding potential is added to the Fock operator. The embedded Hartree-Fock orbitals act as an input for the subsequent ADC calculation which yields the embedded properties (vertical excitation energies, oscillator strengths, etc.). Further information on the FDE-ADC method and FDE-ADC job control are described in Section 11.7.2.1.