INVESTIGADORES
GOMEZ sergio Santiago
artículos
Título:
Relativistic effects on the nuclear magnetic shieldings of rare gas atoms and halogen in hydrogen halides within relativistic polarization propagator theory
Autor/es:
SERGIO S. GOMEZ; ALEJANDRO MALDONADO; GUSTAVO A. AUCAR
Revista:
JOURNAL OF CHEMICAL PHYSICS
Editorial:
AMER INST PHYSICS
Referencias:
Año: 2005 vol. 123 p. 2141081 - 2141087
ISSN:
0021-9606
Resumen:
In this work an analysis of the electronic origin of relativistic effects on the isotropic dia- and paramagnetic contributions to the nuclear magnetic shielding for noble gases and heavy atoms of hydrogen halides is presented. All results were obtained within the 4-component polarization propagator formalism at different level of approach random-phase approximation (RPA)and pure zeroth-order approximation (PZOA), by using a local version of the DIRAC code. From the fact that calculations of diamagnetic contributions to the shieldings within RPA and PZOA approaches for HX(X=Br,I,At) and rare-gas atoms are quite close each to other and the finding that the diamagnetic part of the principal propagator at the PZOA level can be developed as a series (S(D)), it was found that there is a branch of negative-energy “virtual” excitations that contribute with more than 98% of the total diamagnetic value even for the heavier elements, namely, Xe, Rn, I, and At. It contains virtual negative-energy molecular-orbital states with energies between -2mc2and -4mc2. This fact can explain the excellent performance of the linear response elimination of small component (LR-ESC) scheme for elements up to the fifth row in the Periodic Table. An analysis of the convergency of S(D)and its physical implications is given. It is also shown that the total contribution to relativistic effects of the innermost orbital (1s1/2) is by far the largest. For the paramagnetic contribution, a different orbital parten is found for the relativistic contributions vs. the Mass Correction term