A new internally contracted multi-reference configuration interaction method

doi:10.1063/1.3609809

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A new internally contracted multi-reference configuration interaction method

2011-08-01

300

PRE

K. R. Shamasundar *

Gerald Knizia

Werner, Hans-Joachim

DOI：10.1063/1.3609809

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Abstract

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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. (C) 2011 American Institute of Physics. [doi:10.1063/1.3609809]

Keywords:

configuration interactions

orbital calculations

organic compounds

tensors

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