On the Rare-Earth Pnigochalcogenides LnAsSe

Abstract

<jats:title>Abstract</jats:title><jats:p> The structures of GdAsSe and NdAsSe were determined from single crystal data. GdAsSe crystallizes in the monoclinic CeAsS-type structure. The deviations from the parent tetragonal ZrSiS-type structure are smaller than in the corresponding sulphides. The As-As distances in the infinite arsenic chains appear to be too large to warrant non-metallic properties. The structure of NdAsSe is isopuntal with the CeAsS-type; however, only As pairs can be identified. The CeAsS-type structure was also found in the LnAsSe compounds with Ln = Pr, Sm, Tb, . . ., Tm, Lu, Y. The distortions of the ZrSiS-type substructure become more pronounced on going to smaller cations. The stoichiometry of the samples depends strongly upon the preparation.</jats:p>

Probing lattice dynamics and electron-phonon coupling in the topological nodal-line semimetal ZrSiS

“…To correlate our results, let us discuss the geometric structure of tetragonal ZrSiS, isopuntal with PbFCl [49,50] and built up by stacking five 4 4 square nets into layers of [..Si 2 -Zr-S-S-Zr-Si 2 ..] along the fourfold axis. Zr atoms form a part of the double-layer of S atoms and build up sheets of square pyramids [Zr 5/5 S] n , which alternate along c-axis with planer Si 2n layers [49,50]. Si atoms are packed into layers that are twice denser than S layers, resulting appreciable Si-Si bonding and modest S-S bonding into the unit cell structure.…”

“…At around this pressure range, we have noticed that (i) a new mode '1' starts to appear (at ∼17 GPa) and (ii) the softening of E 1 g occurs. To correlate our results, let us discuss the geometric structure of tetragonal ZrSiS, isopuntal with PbFCl [49,50] and built up by stacking five 4 4 square nets into layers of [..Si 2 -Zr-S-S-Zr-Si 2 ..] along the fourfold axis. Zr atoms form a part of the double-layer of S atoms and build up sheets of square pyramids [Zr 5/5 S] n , which alternate along c-axis with planer Si 2n layers [49,50].…”

Contribution to the crystal chemistry of rare earth chalcogenides. I. The compounds with layer structures LnX2

“…The lattice constant parallel to the monoclinic axis c (1 st setting) has to be doubled with respect to the higher symmetric pattern of CeSiFe. Two of the large number of examples are GdSeAs and NdSeAs (Schmelczer et al, 1981). Schmelczer has discussed these selenium compounds and compared them with CeSAs because of the interesting small differences occurring in the zigzag chains.…”

Syntheses, Structures, and Physical Properties of LnAsTe (Ln = La, Pr, Sm, Gd, Dy, Er)

“…A number of structure types are known that contain infinite zigzag chains of groups IIIA−VA elements. These include the structure types CrB, − FeB, ,, MoB, ,, ZrSi 2 , ,− CeNiSi 2 , ,, SmNiGe 3 , β-ZrSb 2 , , HoSb 2 , , CaSb 2 , ,− and CeAsS. − …”