Varadé-López Rebeca, Gómez-Herrero Adrián, Ávila-Brande David, Otero-Díaz L Carlos
Department of Inorganic Chemistry, Faculty of Chemistry, Ciudad Universitaria, Universidad Complutense de Madrid, 28040 Madrid, Spain.
National Center of Electron Microscopy, Universidad Complutense, E-28040, Madrid, Spain.
Inorg Chem. 2020 Apr 6;59(7):4508-4516. doi: 10.1021/acs.inorgchem.9b03657. Epub 2020 Mar 19.
In the present work, two compounds, in the Bi-Nd-Cr-S and Pb-Nd-Nb-Se systems, not reported to date were synthesized. The chemical composition and the structural determination of these complex compounds, at atomic resolution, was performed through conventional and aberration-corrected electron microscopy including selected area electron diffraction, high resolution (HR) transmission electron microscopy (TEM), HR scanning TEM, and the analytical associated techniques X-ray energy-dispersive spectroscopy and electron energy-loss spectroscopy. The average compositions are [(Bi,Nd)S]CrS and (Pb,Nd)Se, respectively. By using these electron microscopy techniques, we confirmed that both compounds can be described in term of two interpenetrated sublattices that fit along but do not fit along , giving rise to an incommensurate modulation. A closer inspection along the stacking direction of the subcell has provided an ideal structural model for [(Bi,Nd)S]CrS based on the intergrowth of one layer of CrS, three atoms thick, (111) B1 type, and one layer of (Bi, Nd)Se, two atoms thick, (100) B1 type. In (Pb,Nd)Se we found that two layers of NbSe, which adopt the 2H-NbSe polytype, alternate with one layer of (Pb, Nd)Se B1 type. In addition, crystals showing extended defects, associated with the weak interaction between the layers, were frequently found.
