Functionalities of MPGRAD, RIMP2, and RICC2

TURBOMOLE offers three possibilities for the calculation of MP2 data. A "conventional" implementation [80], MPGRAD, based on the calculation of four-center integrals (not further developed for several years), and two treatments within the resolution-of-the-identity (RI) approximation: the first and stand-alone implementation [8], RIMP2, and within the coupled-cluster program [10], RICC2.

Functionality of MPGRAD:

• 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.

Functionality of RIMP2:

• Calculation of MP2 energies and/or gradients for RHF and UHF wave functions within the efficient RI-approximation.
• The frozen core approximation is implemented for both RI-MP2 energies and gradients.
• RIMP2 needs optimised auxiliary basis sets, which are available for all TURBOMOLE standard basis sets (SVP, TZVP, TZVPP, QZVPP) as well as for the (aug-)cc-p(wC)VXZ (X = D, T, Q, 5) basis sets series (for Al-Ar also for the (aug-)cc-p(wC)V(X+d)Z series).
• Exploitation of symmetry of all point groups.

Functionality of RICC2:

• Includes the above RIMP2 functionalities.
• Runs parallel.
• See Chapter 9 for further details.