Relativistic effects on nuclear magnetic shielding constants in HX and CH3X (X=Br,I) based on the linear response within the elimination of small component approach

J. I. MELO, M. C. RUIZ DE AZÚA, C. G. GIRIBET, G. A. AUCAR Y P. F. PROVASI

JOURNAL OF CHEMICAL PHYSICS

American Institute of Physics

Lugar: New York; Año: 2004 vol. 121 p. 6798 - 6808

0021-9606

Numerical calculations of relativistic effects on nuclear magnetic shielding corresponding to all one-body operators obtained within a formalism developed in previous work were carried out. In this formalism, the elimination of small component scheme is applied to evaluate all quantities entering a four-component RSPT(2) expression of magnetic molecular properties. HX and CH3X (X=Br, I) were taken as model compounds. Calculations were carried out at the Hartree-Fock level for first order quantities, and at the random-phase approximation (RPA) level for second- and third-order ones. It was found that values of sigma(X) are largely affected by several relativistic corrections not previously considered in the bibliography. Sigma values of the H nucleus are in close agreement with four-component RPA ones. Overall relativistic effects on the shift sigma(X) from HX to CH3X are smaller than nonrelativistic ones.