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 AZUA; C. G. GIRIBETB; G. A. AUCAR; P. F. PROVASI

JOURNAL OF CHEMICAL PHYSICS

American Institute of Physics

Año: 2004 vol. 121 p. 6798 - 6808

0021-9606

Numerical calculations of relativistic effects on nuclear magnetic shielding constants scorresponding to all one-body operators obtained within a formalism developed in previous work [J. I. Melo et al., J. Chem. Phys. 118, 471, 2003] were carried out. In this formalism, theelimination of small component scheme is applied to evaluate all quantities entering afour-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 s(X) are largely affected by several relativistic corrections not previously considered in the bibliography. s values of the H nucleus are in close agreement with four-component RPA ones. Overall relativistic effects on the shift of s(X) from HX to CH3X are smaller than the nonrelativistic shifts.