Local atomic arrangement in LaCuAl3 and LaAuAl3 by NMR and density functional theory

Abstract

CeCuAl3 and CeAuAl3, crystallizing in the non-centrosymmetric BaNiSn3 tetragonal structure, are known mainly for their unusual neutron scattering spectra involving additional excitations ascribed to vibron quasi-bound quantum state in CeCuAl3 and anti-crossing of phonon and crystal field excitations in CeAuAl3. In this work, we present results of nuclear magnetic resonance (NMR) experiments on their lanthanum analogues— and . The character of NMR spectra of , , and 65Cu measured in and is dominated by electric quadrupole interaction. The spectral parameters acquired from experimental data are confronted with values obtained from the electronic structure calculations. The results show remarkable differences for the two compounds. The spectrum in can be interpreted by a single spectral component corresponding to uniform environment of La atoms in the crystal structure, whereas for the spectrum decomposition yields a wide distribution of spectral parameters, which is not possible to explain by a single La environment, and multiple non-equivalent La positions in the crystal structure are required to interpret the spectrum.