Invited lecture: QED and electron correlation effects, and dia- and para-magnetic terms in NMR spectroscopic parameters

GUSTAVO A. AUCAR; CARLOS A. GIMENEZ; KAROL KOZIOL; ALEJANDRO MALDONADO

Grand Forks

Congreso; International Society of Theoretical and Computational Physical Chemistry; 2016

ISTCP

As shown recently, electron correlation and relativistic effects are dependent each other for NMR spectroscopic parameters [1]. Furthermore, the nuclear charge distribution effects may be of the order of 9% for heavy-atom containing molecules [2]. Then one of the next important issue to address for an accurate calculation of magnetic shielding in many-electron systems is related with the likely mutual dependence of electron correlation and QED. How important are electron correlation effects when QED effects are considered? Or the other way around: How large are the electron correlation effects in a QED framework? If they were independent each other one could more easily figure out the way to include both effects in a theoretical scheme.On the other hand, within the relativistic regime spin-restricted calculations are replaced by time-reversal-restricted ones. In the case of NMR J-couplings, there are operators that are of triplet-type (FC and SD) and of singlet-type (PSO) within the NR regime. They can all be considered as paramagnetic-like, within the relativistic regime. One should stress that within this regime there is only one electronic mechanism, which can be divided in two terms: paramagnetic-like and diamagnetic-like.In this presentation we will introduce the newest theoretical framework from which polarization propagators (which are equivalent to double-time Green functions) can be derived, and a model that permits us to get a semi-quantitative estimate of QED effects for NMR magnetic shielding in X-like ions (X = He, Be and Ne) [3]; and the effect of electron correlation within a QED framework. We will also show the behaviour of both, para- and diamagnetic-like terms for J-couplings in the series of compounds XH3Y (X = C, Si, Ge, Sn and Pb; Y = Br and I).[1] G. A. Aucar, R. H. Romero, and A. F. Maldonado, Int. Rev. Phys. Chem. 29, 1 (2010).[2] S. Moncho and J. Autschbach, J. Chem. Theory Comput. 6, 223 (2010); A. F. Maldonado, C. A. Gimenez, and G. A. Aucar, J. Chem. Phys. 136, 224110 (2012).[3] C. A. Gimenez, K. Koziol and G. A. Aucar, Phys Rev A 93, 032504 (2016).