Nuclear-Charge distribution effects on the NMR spectroscopy parameters

A. F. MALDONADO; CARLOS A. GIMENEZ; G. A. AUCAR

Corrientes

Conferencia; Tenth International Conference on Relativisti Effects In Heavy-Elements (REHE); 2012

IMIT, CONICET-UNNE

We present here a study about the influence of the size and type of nuclear charge-distribution models (Gaussian and point-like) on the NMR spectroscopic parameters, the nuclear magnetic shielding σ and the indirect nuclear spin J-coupling. We found that relativistic effects largely enhance the nuclear charge-distribution effects (NChDE) on those parameters being them quite sensitive to the nuclear model adopted for calculations. Results for two rare-gas atoms (Kr, Rn) and few molecular systems like HX, (X = Br, I, At), CH 4 , SnH 4 , SnIH 3 , SnI 2 H 2 and PbIH 3 are presented. J-couplings are more sensitive than shieldings in both, relativistic and non relativistic (NR) regimes. The highest effect (close to 11% of variation in relativistic calculations with that two  different nuclear models) is observed for J(Pb-I) in PbIH 3 . A similar effect is found for J(Pb-H) in the same molecule, close to 9%. The NChDE is lightly dependent on vicinal atoms. For σ(Sn) in SnI 4−n H n with n = 1, 2, 4 it is as large as of few ppm (between 3 to 6.25 ppm). For J(Sn-H) in this set of molecules it goes from 37 Hz for SnH 4 to 54 Hz for SnI 2 H 2 . We also studied the NChDE on the ground state electronic energies of atoms and molecules. We found that these effects are only important within the relativistic regime but not within the NR one. They are in good agreement with previous works.