Goals and Approaches

Available methods include multiconfiguration selfconsistent field (MCSCF), multireference configuration interaction (MRCI) and MR-averaged quadratic coupled cluster (MR-AQCC) methods. For more details see H. Lischka, Th. Müller, P. G. Szalay, I. Shavitt, R. M. Pitzer and R. Shepard

COLUMBUS – A Program System for Advanced Multireference Theory Calculations

Primary COLUMBUS collaboration partners: Thomas Müller (Jülich Supercomputing Centre, Jülich, Germany), Felix Plasser (Loughborough University, Loughborough, UK) and Ron Shepard (Argonne National Laboratory, Argonne, Ill., USA)

Multireference Theory based on Columbus

Recent development:
Local electron correlation treatment based on the weak pair approach

The removal of simultaneous single excitations out of the weak pairs (see picture to the right) is based on the reference doubly occupied space only, leading to a straightforward program implementation and a conceptual simplicity in terms of well-defined localized orbitals. Reductions of up to an order of magnitude in the configuration space expansion and in computer time for the Davidson diagonalization step are found.

More details: A. Das, Th. Müller, F. Plasser, D. B. Krisiloff, E. A. Carter, H. Lischka, J. Chem. Theory Comp. 13 (2017) 2612

R. Lindh et al. COLUMBUS-MOLCAS interface J. Comp. Chem. 37 (2016) 506

H. Lischka et al. The generality of the GUGA MRCI approach in COLUMBUS for treating complex quantum chemistry
Special topic on Electronic Structure Software
J. Chem. Phys. 152 (2020) 134110

P. G. Szalay, Th. Müller, G. Gidofalvi, H. Lischka and R. Shepard
Multiconfiguration self-consistent field and multireference configuration interaction methods and applications
Chem. Rev. 112(2012) 108

H. Lischka, D. Nachtigallová, A. J. A. Aquino, P. G. Szalay, F. Plasser, F. B. C. Machado, and M. Barbatti
Multireference Approaches for Excited States of Molecules
Chem. Rev. 118(2018) 472