Structure du diséléniure de lanthane stoechiométrique LaSe₂. I. Cristaux maclés suivant la loi (100): forme B

The Superstructure of Semiconducting SmTe2−

“…Another interesting fact is that commensurate CDWs have been observed in several rare earth diselenides, in which Se-Se dimerization occurred (8). Similar dimerization and ordered vacancies on Se sheet were observed in RSe (R"Ce, Pr, La) (9,10).…”

“…Low-symmetry space groups such as P4 , P4 and P2/n were tested, but their R values were significantly unfavorable. (7) 0.0157(1) Te (8) 0.039(5) Te (9) 0.039 (1) ?The anisotropic displacement factor exponent takes the form !2 (ha*º # 2 #2hka*b*º ). (6) 3.098(3) -Te (7) 2.80 (2) Te (5)-Te (7) 3.17(2) -Te (8) 2.88(2) -Te (9) 3.12 (2) Te ( In selenium compounds such as LaSe and CeSe , initial square sheets were distorted to generate Se\ dimers forming a 1;2 superstructure (17).…”

“…Anisotropic thermal motions were included (Table 3); however, Te(7), Te (8), and Te(9) were refined only isotropically because of their low occupancies. Some features in thermal ellipsoids were observed (Fig.…”

A low-temperature electron diffraction study of structural disorder and its relationship to the Kondo effect in ThAsSe

“…It usually, however, leads to a long-range ordered superstructure phase as, for example, in the closely related case of LaSe 2 [25] (see, for example, Fig. 2b) where (Se 2 ) 2À dimers are packed in a characteristic herring-bone pattern within (001) planes (thereby doubling one or other of the originally tetragonal basal plane axes) which are also ordered from one such [001] plane to the next.…”

“…Such covalently bonded chalcogenide-chalcogenide dimerization is a common feature of the crystal chemistry of chalcogenides (see e.g., [25,26]). It usually, however, leads to a long-range ordered superstructure phase as, for example, in the closely related case of LaSe 2 [25] (see, for example, Fig.…”