Dresden 2017 – wissenschaftliches Programm
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MM: Fachverband Metall- und Materialphysik
MM 34: Poster session II
MM 34.23: Poster
Dienstag, 21. März 2017, 18:30–20:30, P4
Computional study of Y NMR shielding in intermetallic yttrium compounds — •Leila Kalantari and Peter Blaha — Institute of Material Chemistry, Vienna University of Technology, Getreidemarke 9/165-TC, A-1060 Vienna, Austra
Density functional theory calculations of the magnetic shielding for solid state nuclear magnetic resonance (NMR) provide an important contribution for the understanding of the experimentally observed signals. In this work, we present calculation of the Y NMR shielding in intermetallic compounds. (YM, YMX, YM2X, YM2X2, Y2MB6 and Y2MSi3 where M represents various transition metals and X refers to Si, Ge, Sn). The total shift σ of this selection varies by about 2500 ppm and correlates very well with the experimentally observed shielding except for YMg and YZn. These two simple compounds have a spike in the DOS at EF and a corresponding huge spin susceptibility which lead to the disagreement. The diamagnetic contribution σo (chemical shift) is by no means constant as often assumed when interpreting experimental metallic shifts and varies up to 1700 ppm, but still the dominating term is the spin contact term σc. Although all compounds are metals, only half of them have a paramagnetic (negative) σc due to reoccupation of the valence Y-5s electrons, while for others the induced Y-4d magnetic moment induces diamagnetic core contributions. In all our cases the spin dipolar contribution σsd is fairly small and |σsd| is less than 200 ppm and often even much smaller except in a few very asymmetric compounds like Y2ReB6 (σsd≈450ppm)