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Friday, June 20, 2014
11:00 AM - 12:00 PM
CNLS Conference Room (TA-3, Bldg 1690)

Seminar

Quantum Chemical Topology: on Bonds and Force Fields

Paul Popelier
University of Manchester, Great Britain

Quantum Chemical Topology (QCT)1,2 is an umbrella method that includes QTAIM3,4 as a special case. The central idea of QCT is that of partitioning using a gradient vector field, and apply the language and insights of dynamical systems. Topological atoms are finite-volume, malleable boxes that do not overlap nor leave gaps between them; they exhaust space and form a mosaic of complementary shapes.

This talk has two parts.

The first part5 discusses how to draw a molecule from a molecular wave function. The spatial distribution of atoms in a molecule in the form of chemical graphs is obtained for a set of molecules, using their corresponding domain-averaged exchange-correlation energies (Vxc). Conveniently, such energies are transferable (for 1, n interactions in saturated linear hydrocarbons) and can provide an accurate estimation of the covalent-like contribution between pairs of given interacting topological atoms A and B.

The second part focuses on the electrostatic interaction in a novel topological force field for biomolecular modeling. Topological atoms are boxes with a particular shape and a finite volume. If the coordinates change then the shapes of the atoms change too, as well as their multipole moments. This complex relationship is captured by a machine learning technique called kriging. Here I will explore how these ideas6 can be used to enhance the realism of the electrostatic energy7,8, and put polarisation and charge transfer on the same footing, without having a polarisation catastrophe.

(1) Popelier, P. L. A.; Bremond, E. A. G. Int.J.Quant.Chem. 2009, 109, 2542. (2) Popelier, P. L. A. In Structure and Bonding. Intermolecular Forces and Clusters, Ed, D.J.Wales; Springer: Heidelberg, Germany, 2005; Vol. 115, p 1. (3) Bader, R. F. W. Atoms in Molecules. A Quantum Theory.; Oxford Univ. Press: Great Britain, 1990. (4) Popelier, P. L. A. Atoms in Molecules. An Introduction.; Pearson Education: London, Britain, 2000. (5) Garcia-Revilla, M.; Francisco, E.; Popelier , P. ; Martin-Pendas, A.M. ChemPhysChem 2013, 14, 1211. (6) Popelier, P. L. A. AIP Conf.Proc. 2012, 1456, 261. (7) Mills, M. J. L.; Popelier, P. L. A. Theor.Chem.Acc. 2012, 131, 1137. (8) Kandathil, S. M.; Fletcher, T. L.; Yuan, Y.; Knowles, J.; Popelier, P. J.Comp.Chem. 2013, 34, 1850.

Host: Matt Challacombe