Polarizable embedding (PE) calculations are a based on a hybrid model of quantum mechanics and molecular mechanics (QM/MM) in which the classical region is represented by an electrostatic potential with up to octupole moments and induced point dipole moments. The main improvement over the more common QM/MM approaches without polarizable MM sites can be found for the description of electronic excitations but also for any other process which causes a significant change in the QM density and which is accompanied by a fast response of the environment.
In TURBOMOLE, only ground state energies computed with the dscf, ridft, and ricc2 module and electronic excitation properties based on RI-CC2 are implemented. The general theory is presented in ref.  and , the PERI-CC2 model and the TURBOMOLE implementation is described in ref. .