Nuclear Quadrupole Coupling Constants in Niobium Pentachloride and Related Compounds (II) Transition Metal Nuclei

Abstract

⁹³Nb NQR spectrum in NbCl₅ has been investigated from 4.2 K to 480 K. The coupling constant shows an unusual positive temperature dependence at low temperatures. The EFG tensor is calculated with the d²sp³ octahedral bond functions. The experimental data are analysed in terms of the contributions from the σ- and π-bonds. It is shown that the positive temperature dependence can be explained by the p_π-d_π bond mechanism. The theory is also applied to the related compounds and the consistency with the analysis of the halogen coupling constants is shown.