- Calculation of MP2 energies and/or MP2 gradients for RHF and UHF wave functions.
- The frozen core approximation (possibility to exclude low-lying orbitals from the MP2 treatment) is implemented only for MP2 energies.
- Exploitation of symmetry of all point groups.
- Can be used sequentially or parallel.
- Can be combined with the COSMO solvation model (see chapter 20 for details). (Presently restricted to sequential calculations.)

Functionalities of ricc2 at the MP2-level:

- Calculation of MP2 energies and/or gradients for RHF and UHF wave functions within the efficient RI-approximation (RI-MP2). In geometry optimizations and vibrational frequency calculations (with NumForce) it can be combined with RI-JK-SCF for the Hartre-Fock reference calculation.
- The frozen core approximation is implemented for both energies and gradients.
- RI-MP2 needs optimised auxiliary basis sets, which are available for most standard basis sets as e.g. SVP, TZVP, TZVPP, QZVPP as well as for the (aug-)cc-p(wC)VXZ (X = D, T, Q, 5) basis set series (for Al–Ar also for the (aug-)cc-p(wC)V(X+d)Z series and for p-block elements Ga–Rn also the respective ECP basis set series (-pp)).
- Exploitation of symmetry for all point groups for MP2 energies and gradients.
- Can be combined with the COSMO solvation model (see chapter 20 for details).
- Runs sequentially and parallel (with MPI or OpenMP)
- Contains an implementation of explicitly correlated MP2-F12 methods (presently
restricted to energies and the C
_{1}point group). - Can for open-shell calculations be used with UHF and single-determinant high-spin ROHF reference wavefunctions. (ROHF-MP2 presently limited to energies.)
- Energies and gradients for the spin-component scaled SCS- and SOS-MP2 approaches,
including a Laplace-transformed implementation of SOS-MP2 with (
^{4}) scaling computation costs. - Static polarizabilities (currently restricted to closed-shell reference wavefunctions and the sequential and SMP versions; cannot yet be combined with spin-component scaling), see Chapter 10.5 for a description of the input
- See Chapter 10 for further details.

- Currently restricted to MP2 and DFT double hybrid (e.g. B2PLYP) single point
energy calculations with a closed shell reference determinant and C
_{1}the point group. - Runs sequentially and parallel (with MPI or OpenMP and hybrid MPI/OpenMP).
- Contains an implementation of explicitly correlated PNO-MP2-F12 methods.
- See Section 9.7 for further details.

- For calculations with mpgrad:

Semi-direct MP2 Gradient Evaluation on Workstation Computers: The MPGRAD Program. F. Haase and R. Ahlrichs; J. Comp. Chem. 14, 907 (1993). - For calculations with ricc2:

CC2 excitation energy calculations on large molecules using the resolution of the identity approximation. C. Hättig and F. Weigend; - for MPI parallel calculations with ricc2 in addition:

Distributed memory parallel implementation of energies and gradients for second-order Møller-Plesset perturbation theory with the resolution-of-the-identity approximation. Christof Hättig, Arnim Hellweg, Andreas Köhn, Phys. Chem. Chem. Phys. 8, 1159-1169, (2006). - for MP2-F12 calculations in addition:

The MP2-F12 Method in the TURBOMOLE Programm Package. Rafal A. Bachorz, Florian A. Bischoff, Andreas Glöß, Christof Hättig, Sebastian Höfener, Wim Klopper, David P. Tew, J. Comput. Chem. 32, 2492–2513 (2011). - for (
^{4})-scaling LT-SOS-MP2 calculations:

Scaled opposite-spin CC2 for ground and excited states with fourth order scaling computational costs. Nina O. C. Winter, Christof Hättig, J. Chem. Phys., 134, 184101 (2011) and Scaled opposite-spin second order Møller–Plesset correlation energy: An economical electronic structure method. Y., Jung, R.C. Lochan, A.D. Dutoi, and M. Head-Gordon, J. Chem. Phys., 121, 9793 (2004). - for SCS-MP2 calculations:

S. Grimme, J. Chem. Phys. 118, 9095 (2003). - for RI-MP2 polarizabilities:

Large scale polarizability calculations using the approximate coupled cluster model CC2 and MP2 combined with the resolution-of-the identity approximation. Daniel H. Friese, Nina O. C. Winter, Patrick Balzerowski, Raffael Schwan, Christof Hättig, J. Chem. Phys., 136, 174106 (2012). - for PNO-MP2 calculations: A (
^{3})-scaling PNO-MP2 method using a hybrid OSV-PNO approach with an iterative direct generation of OSVs. Gunnar Schmitz, Benjamin Helmich, Christof Hättig, Mol. Phys. 111, 2463–2476, (2013). - for explicitly correlated PNO-MP2-F12 calculations: Explicitly correlated PNO-MP2 and PNO-CCSD and its application to the S66 set and large molecular systems. Gunnar Schmitz, Christof Hättig, David Tew, Phys. Chem. Chem. Phys. 16, 22167–22178 (2014).