Relativistic quantum chemistry and polarization propagators
Theoretical grounds, some novel physical insights and recent applications
Gustavo A. Aucar
Physics Department, Natural and Exact Science Faculty, Northeastern University of Argentina and IMIT-CONICET. Avda Libertad 5460, Corrientes, Argentina
Polarization propagators are theoretical objects that were first developed within the non relativistic, NR, framework in the 1970’s.[1] Their main applications were focused on response properties, like NMR spectroscopic parameters. Its generalization to the relativistic framework was first presented in the early 1990’s [2] and, after another twenty years, they were found to be nicely obtainable from the path integral formalism, from which one can explain some of the previous findings common to both regimes, NR and relativistic.[3] This new formalism is a natural continuation of what is well known in high-energy physics and so, opened new roads to include QED effects on response properties.
In this lecture I will expose few of the subleties and weakness that appears and are still unsolved in the relativistic quantum chemistry, and then I am going to show some of the new understandings that arises when using polarization propagators within the relativistic framework. I will focus on the physics that underlies the atomic and molecular response properties, and the way to introduce some of the smallest effects (QED and Gaunt) though measurable by today’s experiments, to get accurate theoretical values of NMR spectroscopic parameters. I will also show few of the newest findings, as the likely entanglement between excitations of molecular orbitals.[4]
1. P. Jørgensen and J. Oddershede, J. Chem. Phys. 1972, 57, 277; J. Oddershede, Adv. Quantum Chem. 1978, 11, 257.
2. G. A. Aucar and J. Oddershede, Int. J. Quantum Chem. 1993, 47, 425; G. A. Aucar, T. Saue, L. Visscher and H. J. Aa. Jensen, J. Chem. Phys. 1999, 110, 6208; G. A. Aucar, A. F. Maldonado, M. D. A. Montero and T. Santa Cruz, Int J Quantum Chem. 2019;119:e25722.
3. G. A. Aucar, Phys. Chem. Chem. Phys. 2014, 16, 4420.
4. L. A. Millán, C. G. Giribet and G. A. Aucar, Phys. Chem. Chem. Phys. 2018, 20, 24832.