The Total-Position Spread tensor: a powerful tool to describe the electron behavior in molecular systems

Stefano Evangelisti
Laboratoire de Chimie et Physique Quantiques, Université Paul Sabatier, Toulouse, France.
Vendredi 29 Avril 2016, 10h30
bibliothèque LCT, tour 12 - 13, 4^ème étage

The Total-Position Spread (TPS) tensor, defined as the second moment cumulant of the position operator, is a key quantity to describe the mobility of electrons in a molecule or an extended system [1, 2].
In recent years, we have generalized this formalism by partitioning the tensor with respect to the spin variables [3, 4].

In our investigations, we have shown that, while the Spin-Summed TPS gives information on charge mobility, the Spin-Partitioned TPS tensor becomes a powerful tool that provides information about the mobility of spins. The case of the hydrogen molecule has been treated analytically by using a single Slater-type orbital, and numerically with a V6Z basis set, at Full Configuration Interaction (FCI) level. It is found that at large inter-nuclear distances, the partitioned tensor diverges in some of the low-lying electronic states because of the presence of entanglement in the wave function. Non-dimerized open chains described by a model Hubbard Hamiltonian, and linear hydrogen chains composed of equally spaced atoms have also been studied at FCI level.

Finally, in the case of molecules, we have shown that the TPS tensor gives interesting information on the nature of the molecular and inter-molecular bonds [5, 6].

[1] C. Angeli et al. J. Chem. Phys. 138, 054314 (2013).
[2] M. REl Khatib et al. Chem. Phys. Lett. 591, 58 (2014).
[3] M. El Khati et al. J. Chem. Phys. 142, 094113 (2015).
[4] E. Fertitta et al. J. Chem. Phys. 143, 244308 (2015).
[5] O. Brea et al J. Chem. Theory Comput. 5, 43 (2013).
[6] O. Brea et al J. Phys. Chem. A, in press.