wizyta

od 2020-09-20

Title: Crystal structure, electric field gradient, and electronic charge densities in ReB2: A single crystal X-ray, 11B nuclear magnetic resonance (NMR) and first-principles study

Source: Journal of Applied Physics

Year : 2009

Abstract:

We have grown a single crystal of ReB2 and refined its crystal structure. Our structural studies confirmed the hexagonal structure (space group P6(3)/mmc) with lattice parameters a=2.8982(1) A degrees and c=7.4723(3) A degrees. We also report the observation of first order satellites in the B-11 nuclear magnetic resonance, which indicated the presence of a nonzero quadrupole coupling frequency, nu(Q)=276 ± 3 kHz, and an asymmetry parameter eta=0 at the boron atom sites. These values are in excellent agreement with electric-field-gradient (EFG) tensor calculations based on first principles. These calculations showed that the principal axis of the most negative EFG-tensor component, V-ZZ, is parallel to the c-axis of the crystal. This behavior is in agreement with the observed excess of B p(z) charge (c direction) over the p(x) and p(y) charges and is related to stronger metal-boron bonds compared to previously studied YB12 and LaB6, where the B-B bonds are stronger. Finally, the bonding properties of ReB2 are discussed in terms of densities of states, valence-electron densities, and partial charges.

DOI: 10.1063/1.3190529   (Pobrane:  aktualizowanie)