wizyta

od 2020-09-20

Title: Electric-field gradient tensor and charge densities in LaB6: 11B NMR single-crystal investigations and first-principles calculations

Source: Journal of Applied Physics

Year : 2008

Abstract:

B-11 nuclear-magnetic-resonance measurements on a B-11 enriched single crystal of LaB6 have been performed at room temperature at a frequency of 128.4 MHz. The electric-field-gradient (EFG) tensor components have been determined from the angle dependence of the quadrupole splittings associated with (-3/2 <->-1/2) and (3/2 <-> 1/2) satellite transitions. These EFG components have been calculated using first-principles methods. Very satisfactory agreement with the experimental values has been obtained. The calculations show that the largest component of the EFG tensor mainly comes from the pp part of the so-called sphere component. The principal axis for the most negative EFG component is oriented in direction of the shortest and strongest bond between neighboring B atoms, which belong to two different B-6 units (interoctahedral B-B bonds). The fact that these interoctahedral B-B bonds are aligned in three different directions is responsible for the observation of up to three satellite pairs, although all boron atoms are crystallographically equivalent and there exists only one EFG tensor. Apart from the EFG investigations, chemical bonding in LaB6 is analyzed from densities of states and electron-density plots.
(C) 2008 American Institute of Physics.

DOI: 10.1063/1.2903150   (Pobrane:  2020-10-21)