New understandings of magnetic molecular properties when they are observed from a relativistic framework

GUSTAVO A. AUCAR

Angra dos Reis

Simposio; 17 th Simpósio Brasileiro de Química Teórica (SBQT); 2013

Comité organizador

p { margin-bottom: 0cm; direction: ltr; line-height: 120%; text-align: justify; widows: 2; orphans: 2; }p.western { font-family: "Helvetica",serif; }p.ctl { font-family: "Helvetica"; }a:link { color: rgb(0, 0, 255); } New understandings of magnetic molecular properties when they are observed from a relativistic frameworkGustavo A. Aucar (PQ). gaa@unne.edu.ar Departamento de Física, Facultad de Ciencias Exactas y Naturales, UNNE and Institute of Modelling and Innovative Technology, IMIT (CONICET-UNNE). Avda Libertad 5460, W3404AAS Corrientes, Argentina Keywords: Propagators, NMR, Time-reversal symmetry, Diamagnetism, Virtual pairs. During the last two decades a number of new formalisms were introduced by theoretical quantum chemist to include relativistic effects on the treatment of molecular systems in the best cost/effective way. There are now some quite efficient 4-component and 2-component methods, most of them based on wave functions and DFT theory. They permit us to routinely include relativistic effects on the electronic structure of medium-size heavy-atom containing molecules. The polarization propagator formalism was developed as an alternative approach for studying atomic and molecular properties, first within the nonrelativistic regime and then 20 years later generalized to the relativistic regime1. Within the NR framework they give accurate results when enough electron correlation is included; in practice, till second-order or SOPPA level of approach. Its relativistic counterpart gave new understandings on the subtle origin of atomic and molecular magnetic properties, and some new physical insights that arise only within such a regime2. In this lecture I will expose on how far away one can go today in the analysis and calculation of few atomic and molecular properties working with polarization propagators, till including QED effects3. I will briefly comment on its deepest origin, the path integral formalism, which explains why polarization propagators have the same formal expression in both regimes. This also explains why the NR limit is naturally obtained when the velocity of light is scaled to infinity. The relationship between time-reversal-symmetry with the spin-symmetry, the unification of diamagnetic and paramagnetic contributions in the relativistic domain, the importance of considering virtual pair creations on response properties, the contribution of negative energy one-electron states to electron correlation and how to include QED effects will be shortly highlighted. I will also show the importance of a new effect coined as HAVHA. I will focus on the treatment of the NMR spectroscopic parameters, though most of other response properties can be treated in a similar manner. ACKNOWLEDGMENTS Financial support from two Argentinian institutions, FONCYT and CONICET is greatly appreciated. ____________________ G. A. Aucar and J. Oddershede, Int. J. Quantum Chem.47, 425 (1993). 2 G. A. Aucar, R. H. Romero, A. F. Maldonado, Int. Rev. on Phys. Chem.29, 1 (2010). 3 G. A. Aucar. Perspective article. Phys. Chem. Chem. Phys. In PressDOI: 10.1039/C3CP52685B.