[Todos] IAFE- COLOQUIOS CIENTÍFICOS: Lunes 9 de Noviembre de 2015 a las 14:00 hs .

["Area Difusión IAFE"]

_________________________________________________________________
                          COLOQUIOS CIENTÍFICOS
               Instituto de Astronomía y Física del Espacio
                                 CONICET-UBA
 ___________________________________________________________________________

"Looking for X-ray constrained wave functions: The case of the extremely
localized molecular orbitals."

                              Alessandro Geroni
       CNRS & Université de Lorraine, Laboratoire SRSMC, Nancy & Metz, France
                 Lunes 9 de Noviembre de 2015 a las 14:00 hs.
                         Aula del Edificio IAFE

The determination of wave functions from experimental data has been an
open research field for many years. One of the main reasons that motivated
many research groups to work on this subject is the desire to find a
physically meaningful object able to capture all the data collected from
an experiment. Of course, the wave function represents the best possible
choice from the theoretical point of view because it is the fundamental
entity that intrinsically contains all the information about a system.
Among the different strategies developed in this context, the most
promising technique is probably the X-ray constrained wave function
approach proposed by Jayatilaka [1], a technique that consists in
extracting a single Slater determinant that reproduces a collected set of
experimental diffraction intensities within a predefined accuracy. The
method can be also considered as a practical implementation of the
Henderson & Zimmerman’s idea [2], according to which, of all the
possible single Slater determinants compatible with a given electron
density, the optimal one is that which minimizes the Hartree-Fock energy.
Following this philosophy, we have recently developed a new strategy [3-6]
that combines the technique devised by Jayatilaka with a method proposed
by Stoll and coworkers [7] for the a priori determination of Extremely
Localized Molecular Orbitals (ELMOs), which are molecular orbitals
strictly localized on small molecular fragments such as atoms, bonds or
functional groups. The strength of the novel X-ray constrained ELMO
(XC-ELMO) strategy relies on the fact that it combines the main advantages
associated with the two great families of methods for determining charge
distributions from high-resolution X-ray diffraction data, namely the
quantum mechanical rigor of the wave function- (or orbital-) based
approaches [1, 8] and the easy chemical interpretability of the widely
used multipole models [9, 10]. Our works [3-6] have shown that the
extraction of ELMOs from X-ray diffraction data is straightforward and
that the novel XC-ELMO strategy can be indeed considered as a new useful
tool for the determination and the analysis of electron densities from
X-ray experiments. 1. D. Jayatilaka, D.J. Grimwood, Acta Cryst. A 57, 76
(2001). 2. G. A. Henderson, R. K. Zimmermann, J. Chem. Phys. 65, 619
(1976). 3. A. Genoni, J. Phys. Chem. Lett. 4, 1093 (2013). 4. A. Genoni,
J. Chem. Theory Comput. 9, 3004 (2013). 5. L. H. R. Dos Santos, A. Genoni,
P. Macchi, Acta Cryst. A 70, 532 (2014). 6. A. Genoni, B. Meyer, Adv.
Quantum Chem., in press, doi: 10.1016/bs.aiq.2015.05.008 (2015). 7. H.
Stoll, G. Wagenblast, H. Preuss, Theoret. Chim. Acta 57, 169 (1980). 8. D.
E. Hibbs, S. T. Howard, J. P. Huke, M. P. Waller, Phys. Chem. Chem. Phys.
7, 1772 (2005). 9. R. F. Stewart, Acta Cryst. A 32, 565 (1976). 10. N. K.
Hansen, P. Coppens, Acta Cryst. A 34, 909 (1978). .