Neue Sesquisulfide der Lanthanoide im U2S3-Typ: Tb2S3 und Dy2S3

New sesquisulfides of the lanthanides with the U2S3-type structure (M2S3, M = Tb and Dy) were prepared through the oxidation of TbClH0,67 and DyCl2, respectively, with appropriate amounts of sulfur in the presence of NaCl fluxes in silica protected sealed tantalum containers at 850 °C for at least seven days. The preparation from the elements (2M + 3S; M = Tb and Dy) under otherwise analogous reaction conditions and temperatures was also successful when equimolar fluxes of NaCl were applied. The crystal structure was determined from single crystal data for Tb2S3 and Dy2S3, both crystallizing with the U2S3-type structure (orthorhombic, Pnma, Z = 4; Tb2S3: a = 1067.87(8), b = 388.06(4), c = 1049.07(7) pm ; Dy2S3: a = 1062.45(7), b = 386.59(4), c = 1044.36(8) pm) when prepared under the above-mentioned conditions

Electronic and phononic properties of cinnabar: ab initio calculations and some experimental results

We report ab initio calculations of the electronic band structure, the corresponding optical spectra, and the phonon dispersion relations of trigonal alpha-HgS (cinnabar). The calculated dielectric functions are compared with unpublished optical measurements by Zallen and coworkers. The phonon dispersion relations are used to calculate the temperature and isotopic mass dependence of the specific heat which has been compared with experimental data obtained on samples with the natural isotope abundances of the elements Hg and S (natural minerals and vapor phase grown samples) and on samples prepared from isotope enriched elements by vapor phase transport. Comparison of the calculated vibrational frequencies with Raman and ir data is also presented. Contrary to the case of cubic beta-HgS (metacinnabar), the spin-orbit splitting of the top valence bands at the Gamma-point of the Brillouin zone (Delta_0) is positive, because of a smaller admixture of 5d core electrons of Hg. Calculations of the lattice parameters, and the pressure dependence of Delta_0 and the corresponding direct gap E_0~2eV are also presented. The lowest absorption edge is confirmed to be indirect.Comment: 13 pages, 15 figure

Quaternary Selenides EuLnCuSe3: Synthesis, Structures, Properties and In Silico Studies

In this work, we report on the synthesis, in-depth crystal structure studies as well as optical and magnetic properties of newly synthesized heterometallic quaternary selenides of the Eu+2Ln+3Cu+1Se3 composition. Crystal structures of the obtained compounds were refined by the derivative difference minimization (DDM) method from the powder X-ray diffraction data. The structures are found to belong to orthorhombic space groups Pnma (structure type Ba2MnS3 for EuLaCuSe3 and structure type Eu2CuS3 for EuLnCuSe3, where Ln = Sm, Gd, Tb, Dy, Ho and Y) and Cmcm (structure type KZrCuS3 for EuLnCuSe3, where Ln = Tm, Yb and Lu). Space groups Pnma and Cmcm were delimited based on the tolerance factor t’, and vibrational spectroscopy additionally confirmed the formation of three structural types. With a decrease in the ionic radius of Ln3+ in the reported structures, the distortion of the (LnCuSe3) layers decreases, and a gradual formation of the more symmetric structure occurs in the sequence Ba2MnS3 → Eu2CuS3 → KZrCuS3. According to magnetic studies, compounds EuLnCuSe3 (Ln = Tb, Dy, Ho and Tm) each exhibit ferrimagnetic properties with transition temperatures ranging from 4.7 to 6.3 K. A negative magnetization effect is observed for compound EuHoCuSe3 at temperatures below 4.8 K. The magnetic properties of the discussed selenides and isostructural sulfides were compared. The direct optical band gaps for EuLnCuSe3, subtracted from the corresponding diffuse reflectance spectra, were found to be 1.87– 2.09 eV. Deviation between experimental and calculated band gaps is ascribed to lower d states of Eu2+ in the crystal field of EuLnCuSe3, while anomalous narrowing of the band gap of EuYbCuSe3 is explained by the low-lying charge-transfer state. Ab initio calculations of the crystal structures, elastic properties and phonon spectra of the reported compounds were performed. © 2022 by the authors. Licensee MDPI, Basel, Switzerland.Funding: The research was supported by the Tyumen region within the framework of the grant agreement in the form of a grant to non-profit organizations no. 89-don dated 07.12.2020. This study was supported by the Ministry of Science and Higher Education of the Russian Federation (project no. FEUZ-2020-0054). This work was supported by state assignment of the Ministry of Science and Higher Education of the Russian Federation (Project Reg. No. 720000Ф.99.1.БЗ85АА13000). The work was conducted within the framework of the budget project № 0287-2021-0013 for the Institute of Chemistry and Chemical Technology SB RAS

Crystal structure of hexapraseodymium(III) trinitride tetrasulfide chloride, Pr6N3S4Cl

[no abstract

M3NS3 (M = La-Nd, Sm, Gd-Dy): Structure and magnetism of 3:1:3-type nitride sulfides of trivalent lanthanides

Nitride sulfides of the trivalent lanthanides with the composition M3NS3 (M = La - Nd, Sm, Gd - Dy) can be prepared by the oxidation of the respective lanthanide metal with sulfur, sodium azide (NaN3) and the corresponding lanthanide tribromide (MBr3) when an additional flux (NaBr) is used. Temperature ranges from 800 to 900 degrees C for the thermal treatment of the reaction mixtures in evacuated silica tubes secure the formation of bright to dark brown, transparent, lath shaped single-crystals. The orthorhombic crystal structure (Pnma, Z = 4) was determined from single-crystal X-ray diffraction data (La3NS3: a = 1215.13(5), b = 415.90(2), c = 1322.12(5) pm, Ce3NS3: a = 1206.28(4), b = 410.16(1), c = 1307.18(5) pm, Pr3NS3: a = 1205.45(7), b = 405.35(2), c = 1297.58(8) pm, Nd3NS3: a = 1207.82(5), b = 401.31(1), c = 1295.20(4) pm, Sm3NS3: a = 1201.58(6), b = 394.84(2), c = 1285.63(7) pm, Gd3NS3: a = 1197.17(7), b = 388.22(3), c = 1286.92(8) pm, Tb3NS3: a = 1191.62(7), b = 385.07(3), c = 1282.44(8) pm, and Dy3NS3: a = 1187.66(7), b = 382.55(3), c = 1276.77(8)pm). There are three crystallographically different M3+ cations present in coordination of both the N3- and the S2- anions. However, [NM4](9+) tetrahedra connected via two common corners (c) to form linear chains (1)(infinity){[N(M1)(1/1)(t)(M2)(1/1)(t)(M3)(2/2)(c)](6+)} along [010] build up the main structural feature. A non-linear behaviour for the decreasing lattice constants of the pseudo-isotypic series from La3NS3 to Dy3NS3 concerning the a- and c-axes is observed along with the lanthanoid contraction caused by the diminishing coordination sphere of (M1)(3+) (CN = 7) and (M3)(3+) (CN = 7) moving from the light to the heavier lanthanides. Curie-Weiss-type magnetic behaviour for Dy3NS3 with mu(eff) = 10.3(1) mu(B) for DyN1/3S corresponding to a H-6(15/2) groundstate for Dy3+ at higher temperatures and antiferromagnetic ordering of the Dy3+ moments below 5 K is observed