Foundations of the LRESC model for response properties and some applications

AUCAR, GUSTAVO A.; MELO, JUAN I.; AUCAR, IGNACIO AGUSTÍN; MALDONADO, ALEJANDRO F.

INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY

JOHN WILEY & SONS INC

Año: 2017 vol. 118

0020-7608

Accurate calculations of some response properties, like the NMR spectroscopic parameters, arequite exigent for the theoretical quantum chemistry models together with the computationalcodes that are written from them. They need to include a very good description of the electronicdensity in regions close to the nuclei. When heavy-atom containing systems are studied, thoserequirements become even higher. Given that relativistic effects must be included in one way oranother on the calculation of response properties of heavy-atoms and heavy-atom containing mol-ecules, different schemes were developed during the past decades to include them in as good aspossible way. There are some four-component models, which include relativistic effects in a verycompact way, although calculations have large time-consumption; one also needs to deal withnew and unusual four-component operators. There are also two-component models, which in gen-eral may be less accurate, although their application to property calculations on medium-size andlarge-size molecules are feasible, and they maintain the application of usual operators. In thisreview, we give the fundamentals of the two-component linear response elimination of small com-ponent formalism, LRESC, together with some applications to few selected response properties.New physical insights do appear when the LRESC model is used to analyze the effect of the envi-ronment on magnetic shieldings, and when one search for the relativistic extension of well-knownnonrelativistic relationships like Flygare?s relation among the NMR magnetic shielding and thenuclear spin-rotation constant. A similar relationship is found for the g-tensor and the susceptibil-ity tensor.