Syntheses, Structures, Physical Properties, and Electronic Properties of Some AMUQ₃ Compounds (A = Alkali Metal, M = Cu or Ag, Q = S or Se)

Abstract

The seven new isostructural quaternary uranium chalcogenides KCuUS 3, RbCuUS 3, RbAgUS 3, CsCuUS 3, CsAgUS 3, RbAgUSe 3, and CsAgUSe 3 were prepared from solid-state reactions. These isostructural materials crystallize in the layered KZrCuS 3 structure type in the orthorhombic space group Cmcm. The structure is composed of UQ 6 octahedra and MQ 4 tetrahedra that share edges to form (2) infinity[UMQ 3 (-)] layers. These layers stack perpendicular to [010] and are separated by layers of face- and edge-sharing AQ 8 bicapped trigonal prisms. There are no Q-Q bonds in the structure, so the formal oxidation states of A/U/M/Q may be assigned as 1+/4+/1+/2-, respectively. CsCuUS 3 shows semiconducting behavior with thermal activation energy E a = 0.14 eV and sigma 298 = 0.3 S/cm. From single-crystal absorption measurements in the near IR range, the optical band gaps of these compounds are smaller than 0.73 eV. The more diffuse 5f electrons play a much more dominant role in the optical properties of the AMUQ 3 compounds than do the 4f electrons in the AMLnQ 3 compounds (Ln = rare earth). Periodic DFT spin band-structure calculations on CsCuUS 3 and CsAgUS 3 establish two energetically similar antiferromagnetic spin structures and show magnetic interactions within and between the layers of the structure. Density-of-states analysis shows M-Q orbital overlap in the valence band and U-Q orbital overlap in the conduction band.

Syntheses, structures and properties of five chiral quaternary sulfides, Al x Ln3(Si y Al1−y )S7 (Ln = Y, Gd, Dy) and In0.33Sm3SiS7

“…Generally, the A sites in ALn 3 MQ 7 compounds are occupied by monovalent alkali or coinage metal cations Na + , Ag + and Cu + , or divalent main-group metal cations Mg 2+ . Only three compounds, Al 0.33 Sm 3 SiS 7 [29] , Al 0.44 -La 3 Si 0.93 S 7 [22] and In 0.67 La 6 Si 2 S 14 [23] , have trivalent ions on the A sites. Interestingly, the A sites in 1-5 are occupied by trivalent Al 3+ or In 3+ ions, respectively, indicating that trivalent ions are easy to be introduced to the ALn 3 MQ 7 compounds by our synthetic approach.…”

“…Rare-earth chalcogenides have been intensively investigated in the past years because of their rich structures and properties [1][2][3] . So far as we know, several families of rare-earth chalcogenides have been investigated, such as ALn 3 EQ 7 [4][5][6][7][8][9] , ALnEQ 4 [10][11][12][13] , BaLn 2 MS 5 [14,15] , ALn-MQ 3 (A: alkali or coinage metal; Ln: rare-earth element; E: IV element; M: divalent transition metal; Q: S, Se, Te) [16][17][18][19][20][21] , and so on.…”

“…In ALn 3 EQ 7 family compounds, the atom on the A site is mainly occupied by coinage metal ions (Ag + or Cu + ), and a few are alkali metal or divalent transition metal or Mg 2+ ions. Only two compounds, Al 0.44 La 3 Si 0.93 S 7 [22] and In 0.67 La 6 Si 2 S 14 [23] , were reported with the A site occupied by trivalent main-group metal ions. Besides, no disorder was discovered on the E site which is mostly occupied by IVA element, namely, Si, Ge or Sn atom, except Al 0.44 La 3 Si 0.93 S 7 [22] .…”

“…Only two compounds, Al 0.44 La 3 Si 0.93 S 7 [22] and In 0.67 La 6 Si 2 S 14 [23] , were reported with the A site occupied by trivalent main-group metal ions. Besides, no disorder was discovered on the E site which is mostly occupied by IVA element, namely, Si, Ge or Sn atom, except Al 0.44 La 3 Si 0.93 S 7 [22] . Herein, we report the syntheses, crystal structures, optical and magnetic properties of five new ALn 3 EQ 7 family compounds, Al 0.57 Gd 3 ( (5), in which the A sites are occupied by trivalent Al 3+ or In 3+ ion, and the E sites are occupied by Si and Al jointly in four compounds.…”

Syntheses and characterization of the cubic uranium chalcogenides Rh2U6S15, Cs2Ti2U6Se15, Cs2Cr2U6Se15, and Cs2Ti2U6Te15

“…Many of these compounds such as MU 8 Q 17 [10][11][12][13][14][15][16][17][18] and MUQ 3 [3,12,[19][20][21] contain 3d metals, whereas fewer compounds have been characterized that contain 4d metals. Examples of these include: AAgUQ 3 (A¼Rb, Cs, Q¼ S, Se) [22], A 2 Pd 3 UQ 6 [23], Rh 2 U 6 Se 15.555 [24], CsZrUTe 5 [25], MUQ 3 (M¼ Ru, Rh, Pd, Q¼S, Se) [26,27], A 2 Pd 4 U 6 Q 17 (A ¼Rb, Cs, Q¼S, Se) [28], Mo 6 UQ 8 (Q¼S, Se) [29], Ba 3 AgUS 6 [30], and Ba 9 Ag 10 U 4 S 24 [31]. Because 3d, 4d, and 5d metals differ in size and in preferred coordination environments, it is unlikely that the structure of a given U/3d/Q compound will be the same as those of the corresponding U/4d/Q or U/5d/Q compounds.…”