Energy decompositions in systems with non-nuclear attractors within the theory of atoms in molecules

D.R. ALCOBA; L. LAIN; A. TORRE; R.C. BOCHICCHIO

Londres

Workshop; 12th European Workshop on Quantum Systems in Chemistry and Physics (QSCP-XII); 2007

Royal Holloway University of London

The decomposition of the molecular electronic energy into mono- and diatomic contributions present a great interest allowing one to identify bondings and to describe bonding strengths among the different atoms which compose the chemical systems (molecules, radicals, clusters, etc.). In the last years, a considerable effort has been dedicated to this kind of studies1-3 trying to set up a rigorous and reliable methodology. Some of the described approaches are based on the Bader partitioning of the three-dimensional space into atomic domains known as atoms in molecules theory. In determined situations, the atoms in molecules theory predicts the existence of non-nuclear attractors which are local maxima of electron density out of nuclear positions. The non-nuclear attractors break the generally admitted one-to-one correspondence between atoms and Bader domains, hampering the interpretation of the energy decomposition results4. In this work we deal with the electronic molecular decomposition in systems in which these non-nuclear attractors appear. We propose a working procedure based on a suitable formulation of some overlap matrix elements in terms of effective overlap matrices. We describe three different procedures to formulate the effective overlap integrals which lead to mono- and diatomic partitioning terms with clear chemical meaning. The acetylene and the Li2 molecules have been chosen as test examples to check the proposed algorithms. The calculations have been performed at the Hartree-Fock level although our algorithms can be developed at any level of theory (correlated and uncorrelated wave functions). A comparison between the three methods is performed and the corresponding results are discussed and analyzed in detail. Our technique opens new possibilities within the studies of energy partitionings. REFERENCES: 1  P.L.A. Popelier and D.S. Kosov, J. Chem. Phys. 114, 6539 (2001) 2  I. Mayer, Chem. Phys. Lett. 382, 265 (2003) 3  D.R. Alcoba, A. Torre, L. Lain and R.C. Bochicchio, J. Chem. Phys. 122, 074102 (2005) 4  D.R. Alcoba, L. Lain, A. Torre and R.C. Bochicchio,  Chem. Phys. Lett. 426, 426 (2006)