Rationalization and prediction of rare earth selenide superstructures

• Published in: Journal of the American Chemical Society Vol. 116; no. 1; pp. 154 - 161
• Main Authors: Lee, Stephen, Foran, Brendan
• Format: Journal Article
• Language: English
• Published: United States American Chemical Society 01.01.1994
• Subjects: 360102 - Metals & Alloys- Structure & Phase Studies; 400201 - Chemical & Physicochemical Properties; ALLOYS; CALCULATION METHODS; CHALCOGENIDES; COMPILED DATA; CRYSTAL DEFECTS; CRYSTAL LATTICES; CRYSTAL STRUCTURE; DATA; ELEMENTS; ENERGY LEVELS; FORECASTING; GROUND STATES; INFORMATION; INORGANIC, ORGANIC, PHYSICAL AND ANALYTICAL CHEMISTRY; MATERIALS SCIENCE; MATHEMATICAL MODELS; MOLECULAR ORBITAL METHOD; NUMERICAL DATA; RARE EARTH ALLOYS; SELENIDES; SELENIUM; SELENIUM COMPOUNDS; SEMIMETALS
• ISSN: 0002-7863; 1520-5126
• DOI: 10.1021/ja00080a018

We apply second-moment scaled Huckel theory with inclusion of ionic terms to rationalize or predict superstructures found in elemental selenium, LnQ[sub 2] (Ln = La, Ce; Q = S, Se), Ln[sub 10]Se[sub 19] (Ln = La, Ce, Pr, Nd, Sm), and RbDy[sub 3]Se[sub 8]. All these structures contain distortions of square lattices of chalcogen atoms. In the case of Ln[sub 10]Se[sub 19] and RbDy[sub 3]Se[sub g] these lattice distortions are coupled to ordered defects in the chalcogen square lattice. On the basis of our energy calculations we propose eight ground state RbDy[sub 3]Se[sub 8] superstructure patterns among the 5 x 10[sup 5] possible alternatives. Finally we explain the results of our calculations using HOMO-LUMO and Madelung energy arguments. 23 refs., 14 figs., 4 tabs.