Coloured intermetallic compounds Li2ZnGa and Li2ZnIn

Two coloured Li-containing intermetallic compounds, purple Li2ZnGa and light blue Li2ZnIn, were prepared by induction heating. They were assigned cubic NaTl-type structures (space group Fd3¯m, Z ​= ​8), as determined by powder X-ray diffraction, with cell parameters a of 6.1978(3) Å for Li2ZnGa and 6.5833(4) Å for Li2ZnIn. Solid-state 7Li NMR spectra indicate that the Li atoms occupy a unique site in the crystal structure. The colours were quantified by extracting CIE chromaticity coordinates from optical reflectance spectra, which show high reflectance in the red and blue regions for Li2ZnGa, and in the blue region for Li2ZnIn. These colours likely arise from electronic transitions between local maxima below and above the Fermi level in the density of states.