A new internally contracted multi-reference configuration interaction method

作者：Shamasundar K R^*; Knizia Gerald; Werner Hans Joachim

来源：Journal of Chemical Physics, 2011, 135(5): 054101.

DOI：10.1063/1.3609809

• configuration interactions
• orbital calculations
• organic compounds
• tensors

We present a new internally contracted multi-reference configuration interaction (MRCI) method which, at the same time, efficiently handles large active orbital spaces, long configuration expansions, and many closed-shell orbitals in the reference function. This is achieved by treating the closed-shell orbitals explicitly, so that all required coupling coefficients and density matrices only depend on active orbital labels. As a result, closed-shell orbitals are handled as efficiently as in a closed-shell single-reference program, and this opens up the possibility to perform high-accuracy MRCI calculations for much larger molecules than before. The enormously complex equations are derived using a new domain-specific computer algebra system and semi-automatically implemented using a newly developed integrated tensor framework. The accuracy and efficiency of the MRCI method is demonstrated with applications to dioxygen-copper complexes with different ligands, some of which involve more than 30 atoms, and to spin-state splittings of ferrocene.

• 出版日期2011-8-7