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Accueil > EN > Recruitment > PhD project

Molecular properties in the linear response regime and beyond with relativistic equation of motion coupled cluster

par Johanna Leclercq - publié le

Title of the PhD project :
Molecular properties in the linear response regime and beyond with relativistic equation of motion coupled cluster


Name of the PhD Director :
André Severo Pereira Gomes (andre.gomes@univ-lille.fr)
Name of the co-director or collaborator : Lucas Visscher (l.vissscher@vu.nl)


Laboratories :
PhLAM (Uni. Lille), Section Theoretical Chemistry (VU University Amsterdam)


Financial supports : ED/MESR, thèses labellisées U. Lille


Identified Research Programmes : Labex CaPPA, CPER
CLIMIBIO


Summary of the PhD project :
The study of molecular properties allows us to characterize the electronic structure of atoms, molecules and materials, and with that provide an understanding of the parameters controlling appealing or interesting features (absorption or emission at certain wavelengths etc.). Such properties can be defined as the derivatives of the (electronic) energy of a system with respect to (external or internal perturbations) [1], and in recent years there have been remarkable progresses in their determination in both the linear (electronic excitation spectra, polarizabilities, NMR shieldings etc) and non-linear (hyperpolarizabilities, optical Kerr effect, birefringences etc) regimes via simulations based on the solution of the Schrödinger equation for the electrons, with analytic derivatives techniques and accurate many-body approaches based on the coupled cluster formalism to describe electron correlation. There are cases, however, for which special relativity must be taken into account– notably for containing heavy elements (those at the bottom of the periodic table), or properties related to the innermost electrons of lighter elements such as their X-ray absoprtion and photoelectron spectra–thus calling for the solution of the Dirac equation combined with the coupled cluster approaches [2,3]. In the relativistic case, however, at this time one can only access the same range of molecular properties with more approximate electron correlation based on density functional theory (DFT) [4]. The goal of this thesis is therefore to further develop the relativistic equation of motion coupled cluster approach [5] for the determination of linear and non-linear molecular properties, with a particular focus on properties such as two-photon absorption cross-sections (a non-linear property) as well as mixed electric-magnetic perturbations (that will enable us to simulate magnetic circular dichroism spectra), which can be useful in studying species with complicated electronic structures, with often weak absorption signals such as those containing actinides or other metal centers [6].

[1] ASP Gomes, CR Jacob, Annu. Rep. Sec. C (Phys. Chem). 108, 222, 2012
[2] Y Bouchafra, A Shee, F Real, V Vallet, ASP Gomes, Phys. Rev. Lett. 121, 266001 (2018)
[3] ASP Gomes, L Visscher, H Bolvin, T Saue, S Knecht, T Fleig, E Eliav, J. Chem. Phys., 149, 174113
(2010)
[4] P Tecmer, ASP Gomes, U Ekstrom, L Visscher, Phys. Chem. Chem. Phys., 13, 6249 (2011)
[5] A Shee, T Saue, L Visscher, ASP Gomes, J. Chem. Phys., 149, 174113 (2018)
[6] ASP Gomes, CR Jacob, F Real, L Visscher, V Vallet, Phys. Chem. Chem. Phys., 15, 15153 (2013)