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#

Correlation energies from the Random Phase Approximation

Random Phase Approximation
Ground state energies within the random phase approximation (RPA) can be computed
using the `rirpa` module. The resolution-of-the-identity (RI) approximation is
used to approximate the two-electron repulsion integrals in the correlation
treatment [128,129]. The RI approximation is also employed by default for
the computation of the Coulomb integrals for the HF energy. It is optional to use RI for
the HF exchange integrals.
Functionality of `rirpa`:

- Calculation of RPA energies for RHF and UHF
wave functions.
- The frozen core approximation can be used to exclude
low-lying
occupied orbitals from the RPA treatment.
- RI-K

So far only C_{1} symmetry is supported and the program can only be run
sequentially.

**Subsections**

TURBOMOLE