Structural Transformation in LnHS (Ln = La, Nd, Gd, and Er) with Coordination Change between an S-Centered Octahedron and a Trigonal Prism

Abstract

Lanthanide hydride chalcogenides LnHSe and LnHTe (Ln = lanthanides) crystallize in two polymorphs, 2H and 1H structures (ZrBeSi-type and filled-WC-type structures, respectively), but the chemical origin of the structural selection is unknown. Here, we have expanded the LnHCh (Ch = O, Se, and Te) family to include LnHS (Ln = La, Nd, Gd, and Er) using highpressure synthesis. LnHS adopts the 2H structure for large Ln (La, Nd, and Gd) and the 1H structure for small Er. We compared the two polymorphs using anion-centered polyhedra and found that in the compounds with large ionicity, the 2H structure with ChLn 6 octahedra is stabilized over the 1H structure with ChLn 6 trigonal prisms due to relatively small electrostatic repulsion, supported by analysis of Madelung energy, crystal orbital Hamilton population (COHP), and density of energy (DOE).

Role of Adatom Defects in the Adsorption of Polyaromatic Hydrocarbons on Metallic Substrates

“…Non-planar helicenes generally flatten slightly in the vicinity of the pristine surface: in [6]H, up to four rings become parallel to the surface upon adsorption, thus maximizing dispersive binding interactions, as shown in blue in Figure b,c and discussed at length in ref . Among coinage metal substrates, PAHs bind more strongly to Cu(111) than Ag(111) or Au(111). , This is primarily attributed to the lower-energy location of the metallic d-band in the latter metals (reflected in Figure b, for example), which places more of the resulting antibonding orbitals of the complex below the Fermi level. − …”

Anionic Sublattices in Halide Solid Electrolytes: A Case Study with the High‐Pressure Phase of Li3ScCl6

“…Our recent study on lanthanide hydride chalcogenides also found that there is an apparent covalent stabilization in the high-pressure phases of LnHS (Ln = La, Nd, Gd, and Er) with ChLn 6 prismatic coordination compared to octahedral (anti-prismatic) coordination, which was supported by integrated crystal orbital Hamilton population (ICOHP) calculations. [28] The switching of anion sublattices is validated by density-functional theory (DFT) calculations, comparing enthalpies of formation as a function of pressure for both the γ-Li 3 ScCl 6 and α-Li 3 ScCl 6 phases; note that in the γ phase, a 2×1×2 supercell with ordered lithium and Sc vacancies is constructed. As shown in Figure 4, the γ phase stabilizes over the α phase above a critical pressure of about 3.7 GPa.…”

Role of adatom defects in the adsorption of polyaromatic hydrocarbons on metallic substrates

“…Among coinage metal substrates, PAHs bind more strongly to Cu(111) than Ag(111) or Au(111) 1,47. This is primarily attributed to the lower-energy location of the metallic d-band in the latter metals [reflected in Figure3(b), for example], which places more of the resulting antibonding orbitals of the complex below the Fermi level [48][49][50][51]…”