************OWARI COMPLEX SEMINAR LXIX*************

Title：X-ray Constrained Wave Function Methods: 
       Recent Studies and New Perspectives

Speaker：Alessandro Genoni

Affiliation：Universite de Lorraine

Date：Tue. Nov. 1st, 3:00 pm (Almost one hour)

Place：3rd Lecture Room (1F), 
       Graduate School of Information Science

Abstract:
The determination of wave functions (or density 
matrices) directly from experimental data is an 
attractive perspective that stimulated different 
research groups over the years. The main 
motivation underling this topic is certainly the 
possibility of summarizing all the information 
obtained from an experiment into an object of 
unquestionable physical meaning. Although several 
strategies have been developed in this context, 
nowadays the most promising strategy is the X-ray 
constrained wave function (XC-WF) approach 
introduced by Jayatilaka [1], a technique that 
consists in extracting a plausible single Slater 
determinant that enables to reproduce experimental 
X-ray diffraction data within a desired accuracy. 
In this context, we have recently combined the 
XC-WF strategy with the Stoll approach [2] for the 
determination of Extremely Localized Molecular 
Orbitals (ELMOs), namely Molecular Orbitals 
strictly localized on small molecular fragments, 
such as atoms, bonds or functional groups. The 
extraction of ELMOs from X-ray diffraction data 
is really straightforward and our 
investigations [3-5] have revealed that the novel 
XC-ELMO technique could become an alternative to 
the widely used multipole model methods [6] for 
the determination and the analysis of experimental 
electron densities. Nevertheless, notwithstanding 
their advantages, all the modern XC-WF approaches 
are also characterized by some crucial and still 
open problems. One of them concerns the capability 
of these techniques in capturing at least a part 
of the electron correlation effects on the electron 
densities. In this regard, we have performed test 
calculations [7] that allowed us to determine the 
optimal conditions under which (namely, the 
optimal resolution at which) the XC-WF strategies 
significantly retrieve the correlation effects.

References
(1) D. Jayatilaka, D. J. Grimwood, 
Acta Cryst A 57, 76 (2001).
(2) H. Stoll, G. Wagenblast, H. Preuss, 
Theoret. Chim. Acta 57, 169 (1980).
(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, 
Axta Cryst. A 70, 532 (2014).
(6) R. F. Stewart, Acta Cryst. A 32, 565 (1976); 
N. K. Hansen, P. Coppens, Acta Cryst. A 
34, 909 (1978).
(7) A. Genoni, L. H. R. Dos Santos, B. Meyer, 
P. Macchi, IUCrJ, submitted.

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