Synthesis and characterization of six new quaternary actinide thiophosphate compounds: Cs(8)U(5)(P(3)S(10))(2)(PS(4))(6)(,) K(10)Th(3)(P(2)S(7))(4)(PS(4))(2), and A(5)An(PS(4))(3), (A = K, Rb, Cs; An = U, Th)

Six new actinide metal thiophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction: Cs(8)U(5)(P(3)S(10))(2)(PS(4))(6) (I), K(10)Th(3)(P(2)S(7))(4)(PS(4))(2) (II), K(5)U(PS(4))(3) (III), K(5)Th(PS(4))(3) (IV), Rb(5)Th(PS(4))(3) (V), and Cs(5)Th(PS(4))(3) (VI). Compound I crystallizes in the monoclinic space group P2(1)/c with a = 33.2897(1) A, b = 14.9295(1) A, c = 17.3528(2) A, beta = 115.478(1) degrees, Z = 8. Compound II crystallizes in the monoclinic space group C2/c with a = 32.8085(6) A, b = 9.0482(2) A, c = 27.2972(3) A, beta = 125.720(1) degrees, Z = 8. Compound III crystallizes in the monoclinic space group P2(1)/c with a = 14.6132(1) A, b = 17.0884(2) A, c = 9.7082(2) A, beta = 108.63(1) degrees, Z = 4. Compound IV crystallizes in the monoclinic space group P2(1)/n with a = 9.7436(1) A, b = 11.3894(2) A, c = 20.0163(3) A, beta = 90.041(1) degrees, Z = 4, as a pseudo-merohedrally twinned cell. Compound V crystallizes in the monoclinic space group P2(1)/c with a = 13.197(4) A, b = 9.997(4) A, c = 18.189(7) A, beta = 100.77(1) degrees, Z = 4. Compound VI crystallizes in the monoclinic space group P2(1)/c with a = 13.5624(1) A, b = 10.3007(1) A, c = 18.6738(1) A, beta = 100.670(1) degrees, Z = 4. Optical band-gap measurements by diffuse reflectance show that compounds I and III contain tetravalent uranium as part of an extended electronic system. Thorium-containing compounds are large-gap materials. Raman spectroscopy on single crystals displays the vibrational characteristics expected for [PS(4)](3)(-), [P(2)S(7)](4-), and the new [P(3)S(10)](5)(-) building blocks. This new thiophosphate building block has not been observed except in the structure of the uranium-containing compound Cs(8)U(5)(P(3)S(10))(2)(PS(4))(6).     

Synthesis,crystal structure and optical properties of A3Zr2P5S18 (A=Rb,Cs): the first quaternary zirconium thiophosphates

The first quaternary zirconium thiophosphates Rb₃Zr₂P₅S₁₈ (1) and Cs₃Zr₂P₅S₁₈ (2) were synthesized by reacting ZrS₂ with an in situ formed melt of A₂S₃ (A=Rb, Cs), P₂S₅ and S. The compounds are isostructural and crystallize in the monoclinic space group Cc with Z=4. Compound 1 has cell parameters a=9.248(2) Å, b=9.860(2) Å, c=33.622(7) Å and β=94.73(3)° and compound 2 a=9.288(2) Å, b=9.956(2) Å, c=34.061(7) Å and β=94.26(3)°. The structures are composed of a two-dimensional anionic layer [Zr₂P₅S₁₈]³⁻ and intervening alkali cations. Each of the two independent Zr atoms is surrounded by seven S atoms yielding a distorted pentagonal bipyramid. The ZrS₇ polyhedra are interconnected into the final layered anion by [P₂S₇] groups which act in an unusual edge- and corner-sharing mode and by edge-sharing [PS₄] tetrahedra. Compound 2 was characterized with MIR and UV/vis diffuse reflectance spectroscopy.     

Rb(3)Ti(3)(P(4)S(13))(PS(4))(3) and Cs(2)Ti(2)(P(2)S(8))(PS(4))(2): two polar titanium thiophosphates with complex one-dimensional tunnels

The reactions of Ti with in situ formed polythiophosphate fluxes of A(2)S(3) (A = Rb, Cs), P(2)S(5), and S at 500 degrees C result in the formation of two new quaternary titanium thiophosphates with compositions Rb(3)Ti(3)(P(4)S(13))(PS(4))(3) (1) and Cs(2)Ti(2)(P(2)S(8))(PS(4))(2) (2). Rb(3)Ti(3)(P(4)S(13))(PS(4))(3) (1) crystallizes in the chiral hexagonal space group P6(3) (No. 173) with lattice parameters a = 18.2475(9) Angstrom, c = 6.8687(3) Angstrom, V = 1980.7(2) Angstrom(3), Z = 2. Cs(2)Ti(2)(P(2)S(8))(PS(4))(2) (2) crystallizes in the noncentrosymmetric monoclinic space group Cc (No. 9) with a = 21.9709(14) Angstrom, b = 6.9093(3) Angstrom, c = 17.1489(10) Angstrom, beta = 98.79(1) degrees, V = 2572.7(2) Angstrom(3), Z = 4. In the structure of 1 TiS(6) octahedra, three [PS(4)] tetrahedra, and the hitherto unknown [P(4)S(13)](6-) anion are joined to form two different types of helical chains. These chains are connected yielding two different helical tunnels being directed along [001]. The tunnels are occupied by the Rb+ ions. The [P(4)S(13)](6-) anion is generated by three [PS(4)] tetrahedra sharing corners with one [PS(4)] group in the center of the starlike anion. The P atoms of the three [PS(4)] tetrahedra attached to the central [PS(4)] group define an equilateral triangle. The [P(4)S(13)](6-) anion may be regarded as a new member of the [P(n)S(3n+1)]((n+2)-) series. The structure of Cs(2)Ti(2)(P(2)S(8))(PS(4))(2) (2) consists of the one-dimensional polar tunnels containing the Cs(+) cations. The rare [P(2)S(8)](4-) anion which is composed of two [PS(4)] tetrahedra joined by a S(2)(2-) anion is a fundamental building unit in the structure of 2. One-dimensional undulated chains being directed along [100] are joined by [PS(4)] tetrahedra to form the three-dimensional network with polar tunnels running along [010]. The compounds are characterized with IR, Raman spectroscopy, and UV/vis diffuse reflectance spectroscopy.     

Synthesis and structural characterization of quaternary thorium selenophosphates: A2ThP3Se9 (A = K, Rb) and Cs4Th2P5Se17

Single crystals of A2ThP3Se9 (A = K (I), Rb (II)) and Cs4Th2PsSe17 (III) form from the reaction of Th and P in a molten A2Se3/Se (A = K, Rb, Cs) flux at 750 degrees C for 100 h. Compound I crystallizes in the triclinic space group P1 (No. 2) with unit cell parameters a = 10.4582(5) A, b = 16.5384(8) A, c = 10.2245(5) A, alpha = 107.637(1); beta = 91.652(1); gamma = 90.343(1) degrees, and Z = 2. Compound II crystallizes in the triclinic space group P1 (No. 2) with the unit cell parameters a = 10.5369(5) A, b = 16.6914(8) A, c = 10.2864(5) A, alpha = 107.614(1) degrees, beta = 92.059(1) degrees, gamma = 90.409(1) degrees, and Z = 2. These structures consist of infinite chains of corner-sharing [Th2Se14] units linked by (P2Se6)4- anions in two directions to form a ribbonlike structure along the [100] direction. Compounds I and II are isostructural with the previously reported K2UP3Se9. Compound III crystallizes in the monoclinic space group P2(1)/c (No. 14) with unit cell parameters a = 10.238(1) A, b = 32.182(2) A, c = 10.749(1) A; beta = 95.832(1) degrees, and Z = 4. Cs4Th2P5Se17 consists of infinite chains of corner-sharing, polyhedral [Th2Se13] units that are also linked by (P2Se6)4- anions in the [100] and [010] directions to form a layered structure. The structure of III features an (Se2)2- anion that is bound eta 2 to Th(2) and eta 1 to Th(1). This anion influences the coordination sphere of the 9-coordinate Th(2) atom such that it is best described as bicapped trigonal prismatic where the eta 2-bound anion occupies one coordination site. The composition of III may be formulated as Cs4Th2(P2Se6)5/2(Se2) due to the presence of the (Se2)2- unit. Raman spectra for these compounds and their interpretation are reported.     

Aluminosilicate relatives: Chalcogenoaluminogermanates Rb(3)(AlQ(2))(3)(GeQ(2))(7) (Q = S, Se)

The new compounds Rb(3)(AlQ(2))(3)(GeQ(2))(7) [Q = S (1), Se (2)] feature the 3D anionic open framework [(AlQ(2))(3)(GeQ(2))(7)](3-) in which aluminum and germanium share tetrahedral coordination sites. Rb ions are located in channels formed by the connection of 8, 10, and 16 (Ge/Al)S(4) tetrahedra. The isostructural sulfur and selenium derivatives crystallize in the space group P2(1)/c. 1: a = 6.7537(3) ?, b = 37.7825(19) ?, c = 6.7515(3) ?, and β = 90.655(4)°. 2: a = 7.0580(5) ?, b = 39.419(2) ?, c = 7.0412(4) ?, β = 90.360(5)°, and Z = 2 at 190(2) K. The band gaps of the congruently melting chalcogenogermanates are 3.1 eV (1) and 2.4 eV (2).     

Mixed-metal uranium(VI) iodates: hydrothermal syntheses,structures, and reactivity of Rb[UO(2)(CrO(4))(IO(3))(H(2)O)], A(2)[UO(2)(CrO(4))(IO(3))(2)] (A = K,Rb, Cs), and K(2)[UO(2)(MoO(4))(IO(3))(2)

The reactions of the molecular transition metal iodates A[CrO(3)(IO(3))] (A = K, Rb, Cs) with UO(3) under mild hydrothermal conditions provide access to four new, one-dimensional, uranyl chromatoiodates, Rb[UO(2)(CrO(4))(IO(3))(H(2)O)] (1) and A(2)[UO(2)(CrO(4))(IO(3))(2)] (A = K (2), Rb (3), Cs (4)). Under basic conditions, MoO(3), UO(3), and KIO(4) can be reacted to form K(2)[UO(2)(MoO(4))(IO(3))(2)] (5), which is isostructural with 2 and 3. The structure of 1 consists of one-dimensional[UO(2)(CrO(4))(IO(3))(H(2)O)](-) ribbons that contain uranyl moieties bound by bridging chromate and iodate anions as well as a terminal water molecule to create [UO(7)] pentagonal bipyramidal environments around the U(VI) centers. These ribbons are separated from one another by Rb(+) cations. When the iodate content is increased in the hydrothermal reactions, the terminal water molecule is replaced by a monodentate iodate anion to yield 2-4. These ribbons can be further modified by replacing tetrahedral chromate anions with MoO(4)(2)(-) anions to yield isostructural, one-dimensional [UO(2)(MoO(4))(IO(3))(2)](2)(-) ribbons. Crystallographic data: 1, triclinic, space group P(-)1, a = 7.3133(5) A, b = 8.0561(6) A, c = 8.4870(6) A, alpha = 88.740(1) degrees, beta = 87.075(1) degrees, gamma = 71.672(1) degrees, Z = 2; 2, monoclinic, space group P2(1)/c, a = 11.1337(5) A, b = 7.2884(4) A, c = 15.5661(7) A, beta = 107.977(1) degrees, Z = 4; 3, monoclinic, space group P2(1)/c, a = 11.3463(6) A, b = 7.3263(4) A, c = 15.9332(8) A, beta = 108.173(1) degrees, Z = 4; 4, monoclinic, space group P2(1)/n, a = 7.3929(5) A, b = 8.1346(6) A, c = 22.126(2) A, beta = 90.647(1) degrees, Z = 4; 5, monoclinic, space group P2(1)/c, a = 11.3717(6) A, b = 7.2903(4) A, c = 15.7122(8) A, beta = 108.167(1) degrees, Z = 4.     

A new quaternary thiophosphate,RbNb2(S2)3(PS4)

The structure of the new quaternary thio­phosphate rubidium diniobium tris­(di­sulfide) tetra­thio­phosphate, RbNb₂(S₂)₃(PS₄), is made up of one‐dimensional [Nb₂(S₂)₃(PS₄)^?] chains along the [101] direction, and these chains are separated from one another by Rb⁺ ions. The chain is basically built up from [Nb₂S₁₂] units and tetrahedral [PS₄] groups. The [Nb₂S₁₂] units are linked together to form a linear [Nb₂S₉] chain by sharing the S–S prism edge. Short and long Nb—Nb distances [2.888 (2) and 3.760 (2) Å, respectively] alternate along the chain, and the anionic species S₂^2? and S^2? are observed.     

Syntheses and characterization of nine quaternary uranium chalcogenides among the compounds A2M3UQ6 (A = K, Rb, Cs; M = Pd, Pt; Q = S, Se)

Nine compounds from the series A(2)M(3)UQ(6) (A = K or Rb or Cs; M = Pd or Pt; Q = S or Se) were synthesized by reacting U, M, and Q in ACl or A(2)Q(x) fluxes. These compounds crystallize with eight formula units in the NaBa(2)Cu(3)O(6) structure type, in space group Fmmm of the orthorhombic system. The structure contains hexagons formed from six edge-sharing square-planar coordinated M atoms, which in turn edge-share with trigonal-prismatically coordinated U atoms, forming layers along (010). These layers are separated by A atoms. Electrical resistivity measurements along the [100] direction of Rb(2)Pd(3)US(6) show typical semiconductor behavior. Magnetic susceptibility measurements on Rb(2)Pd(3)US(6) display marked magnetic anisotropy and unusually low magnetic moments owing to crystalline electric field effects.     

Synthesis and characterization of AU2Se6 (A = K, Cs)

Two new ternary uranium selenides, AU(2)Se(6) (A = K, Cs), were prepared using the reactive flux method. Single crystal X-ray diffraction was performed on single crystals. The compounds crystallize in the orthorhombic Immm space group, Z = 2. CsU(2)Se(6) has cell parameters of a = 4.046(2) A, b = 5.559(3) A, and c = 24.237(12) A. KU(2)Se(6) has cell parameters of a = 4.058(3) A, b = 5.556(4) A, and c = 21.710(17) A. The compounds are isostructural to the previously reported KTh(2)Se(6). The two-dimensional layered structure is related to ZrSe(3) with the alkali metals residing in the interlayer space. The oxidation states of uranium and selenium were evaluated using X-ray photoelectron spectroscopy (XPS). Uranium was found to be tetravalent, while selenium was found to be in two oxidation states, one of which is -2. The other oxidation state is similar to that found in a polyselenide network. While this structure is known, our work examines how the structure changes through the transactinide series.     

MZr2（AsO4）3（M=Na,K,Rb,Cs）的水热合成与结构表征

用水热晶化法合成了MZr_2(ASO_4)_3(M=Na,K,Rb,Cs)系列化合物。研究了反应物浓度、配比及不同砷源等水热晶化条件对产物物相的影响。用XRD、IR和Raman光谱对产物进行了表征。4种晶体的振动光谱由钠到铯呈现出规律性变化。     

Structural characterization of the first hydroxo-bridged plutonium compound, (PuO(2))(2)(IO(3))(mu(2)-OH)(3)

The hydrothermal reaction of a (239)Pu(IV) stock solution in the presence of iodic acid and 1 M KOH produces reddish-brown single crystals of (PuO(2))(2)(IO(3))(OH)(3). The structure consists of two-dimensional layers forming in the ac plane and is the first single-crystal structure of plutonium(VI) connected through hydroxide anions. The additional linkage of plutonium centers is completed through iodate ligands.     

Thiophosphate phase diagrams developed in conjunction with the synthesis of the new compounds KLaP(2)S(6), K(2)La(P(2)S(6))(1/2)(PS(4)), K(3)La(PS(4))(2), K(4)La(0.67)(PS(4))(2), K(9-)(x)La(1+x/3)(Ps(4))(4) (x = 0.5), K(4)Eu(PS(4))(2), and KEuPS(4)

An alkali-metal sulfur reactive flux has been used to synthesize a series of quaternary rare-earth metal compounds. These include KLaP(2)S(6) (I), K(2)La(P(2)S(6))(1/2)(PS(4)) (II), K(3)La(PS(4))(2) (III), K(4)La(0.67)(PS(4))(2) (IV), K(9-x)La(1+x/3)(PS(4))(4) (x = 0.5) (V), K(4)Eu(PS(4))(2) (VI), and KEuPS(4) (VII). Compound I crystallizes in the monoclinic space group P2(1)/c with the cell parameters a = 11.963(12) A, b = 7.525(10) A, c = 11.389(14) A, beta = 109.88(4) degrees, and Z = 4. Compound II crystallizes in the monoclinic space group P2(1)/n with a = 9.066(6) A, b = 6.793(3) A, c = 20.112(7) A, beta = 97.54(3) degrees, and Z = 4. Compound III crystallizes in the monoclinic space group P2(1)/c with a= 9.141(2) A, b = 17.056(4) A, c = 9.470(2) A, beta = 90.29(2) degrees, and Z = 4. Compound IV crystallizes in the orthorhombic space group Ibam with a = 18.202(2) A, b = 8.7596(7) A, c = 9.7699(8) A, and Z = 4. Compound V crystallizes in the orthorhombic space group Ccca with a = 17.529(9) A, b = 36.43(3) A, c = 9.782(4) A, and Z = 8. Compound VI crystallizes in the orthorhombic space group Ibam with a = 18.29(5) A, b = 8.81(2) A, c= 9.741(10) A, and Z = 4. Compound VII crystallizes in the orthorhombic space group Pnma with a = 16.782(2) A, b = 6.6141(6) A, c = 6.5142(6) A, and Z = 4. The sulfur compounds are in most cases isostructural to their selenium counterparts. By controlling experimental conditions, these structures can be placed in quasi-quaternary phase diagrams, which show the reaction conditions necessary to obtain a particular thiophosphate anionic unit in the crystalline product. These structures have been characterized by Raman and IR spectroscopy and UV-vis diffuse reflectance optical band gap analysis.     

Synthesis and Characterization of the Rubidium Thiophosphate Rb6(PS5)(P2S10) and the Rubidium Silver Thiophosphates Rb2AgPS4, RbAg5(PS4)2 and Rb3Ag9(PS4)4

The metal thiophosphates Rb₂AgPS₄ ( 2 ), RbAg₅(PS₄)₂ ( 3 ), and Rb₃Ag₉(PS₄)₄ ( 4 ) were synthesized by stoichiometric reactions, whereas Rb₆(PS₅)(P₂S₁₀) ( 1 ) was prepared with excess amount of sulfur. The compounds crystallize as follows: 1 monoclinic, P2₁/c (no. 14), a = 17.0123(7) Å, b = 6.9102(2) Å, c = 23.179(1) Å, β = 94.399(4)°; 2 triclinic, P$\bar{1}$ (no. 2), a = 6.600(1) Å, b = 6.856(1) Å, c = 10.943(3) Å, α = 95.150(2)°, β = 107.338(2)°, γ = 111.383(2)°; 3 orthorhombic, Pbca (no. 61), a = 12.607(1) Å, b = 12.612(1) Å, c = 17.759(2) Å; 4 orthorhombic, Pbcm (no. 57), a = 6.3481(2) Å, b = 12.5782(4) Å, c = 35.975(1) Å. The crystal structures contain discrete units, chains, and 3D polyanionic frameworks composed of PS₄ tetrahedral units arranged and connected in different manner. Compounds 1 – 3 melt congruently, whereas incongruent melting behavior was observed for compound 4 . 1 – 4 are semiconductors with bandgaps between 2.3 and 2.6 eV and thermally stable up to 450 °C in an inert atmosphere.     

Mixed Alkali Neodymium Orthoborates: K9Li3Nd3(BO3)7 and A2LiNd(BO3)2 (A = Rb,Cs)

Crystals of mixed alkali neodymium orthoborates, K₉Li₃Nd₃(BO₃)₇ and A₂LiNd(BO₃)₂ (A = Rb, Cs) were obtained by spontaneous crystallization. K₉Li₃Nd₃(BO₃)₇ crystallizes in space group P2/c with cell parameters of a = 11.4524(7) Å, b = 10.1266(6) Å, c = 12.3116 (10) Å, β = 122.0090(10)°. In the structure, NdO₈ polyhedra share corners and connect with planer BO₃ groups to form infinite [Nd₃B₃O₂₁]_n chains. These chains are linked by additional BO₃ groups to produce a double layer of [Nd₆B₆O₃₈]_n blocks in the ac plane with K and Li ions filled into the cavities. A₂LiNd(BO₃)₂ (A = Rb, Cs) crystallizes in space group Pbcm, with cell parameters of a = 7.113(2) Å, b = 9.691(3) Å and c = 10.135(3) Å for Rb₂LiNd(BO₃)₂, and a = 7.2113(3) Å, b = 9.9621(4) Å, and c = 10.3347(4) Å for Cs₂LiNd(BO₃)₂. In the structure, NdO₈ polyhedra are corner‐sharing with each other and further interlinked by BO₃ groups to comprise the infinite [Nd₄B₄O₂₄] sheets in the bc plane, with Rb/Cs and Li ions occupying the interlayered space. The compounds show effective near‐IR emission and their associated lifetimes are obtained by fluorescence spectra.     

Hydrothermal syntheses, structures, and properties of the new uranyl selenites Ag(2)(UO(2))(SeO(3))(2), M[(UO(2))(HSeO(3))(SeO(3))] (M = K, Rb, Cs, Tl), and Pb(UO(2))(SeO(3))(2)

The transition metal, alkali metal, and main group uranyl selenites, Ag(2)(UO(2))(SeO(3))(2) (1), K[(UO(2))(HSeO(3))(SeO(3))] (2), Rb[(UO(2))(HSeO(3))(SeO(3))] (3), Cs[(UO(2))(HSeO(3))(SeO(3))] (4), Tl[(UO(2))(HSeO(3))(SeO(3))] (5), and Pb(UO(2))(SeO(3))(2) (6), have been prepared from the hydrothermal reactions of AgNO(3), KCl, RbCl, CsCl, TlCl, or Pb(NO(3))(2) with UO(3) and SeO(2) at 180 degrees C for 3 d. The structures of 1-5 contain similar [(UO(2))(SeO(3))(2)](2-) sheets constructed from pentagonal bipyramidal UO(7) units that are joined by bridging SeO(3)(2-) anions. In 1, the selenite oxo ligands that are not utilized within the layers coordinate the Ag(+) cations to create a three-dimensional network structure. In 2-5, half of the selenite ligands are monoprotonated to yield a layer composition of [(UO(2))(HSeO(3))(SeO(3))](1-), and coordination of the K(+), Rb(+), Cs(+), and Tl(+) cations occurs through long ionic contacts. The structure of 6 contains a uranyl selenite layered substructure that differs substantially from those in 1-5 because the selenite anions adopt both bridging and chelating binding modes to the uranyl centers. Furthermore, the Pb(2+) cations form strong covalent bonds with these anions creating a three-dimensional framework. These cations occur as distorted square pyramidal PbO(5) units with stereochemically active lone pairs of electrons. These polyhedra align along the c-axis to create a polar structure. Second-harmonic generation (SHG) measurements revealed a response of 5x alpha-quartz for 6. The diffuse reflectance spectrum of 6 shows optical transitions at 330 and 440 nm. The trailing off of the 440 nm transition to longer wavelengths is responsible for the orange coloration of 6.     

Zintl-Verbindungen mit Gold: M3AuSn4 mit M = K,Rb, Cs und M3AuPb4 mit M = Rb,Cs

Zintl-Compounds with Gold: M₃AuSn₄ with M = K, Rb, Cs and M₃AuPb₄ with M = Rb, Cs Silver coloured, brittle single crystals of the compounds M₃AuSn₄ with M = K, Rb, Cs and M₃AuPb₄ with M = Rb, Cs were synthesized by reactions of alkali metal azides (MN₃) with gold sponge and tin (lead) powder at T = 923 K. The structures of the isotypic compounds (space group Pmmn, Z = 2) were determined from X-ray single-crystal diffractometry data (see ‘‘Inhaltsübersicht”︁”︁). The Zintl-compounds M₃AuE(14)₄ with E(14) = Sn, Pb contain [AuE(14)₄]-chains with P₄-analogous E(14)₄-tetrahedra which are connected by μ₂-bridging gold atoms.     

Synthesis and characterization of two quaternary thorium chalcophosphates: Cs4Th2P6S18 and Rb7Th2P6Se21

Two new thorium chalcophosphates have been synthesized by the reactive flux method and characterized by single-crystal X-ray diffraction, diffuse reflectance, and Raman spectroscopy: Cs4Th2P6S18 (I); Rb7Th2P6Se21 (II). Compound I crystallizes as colorless blocks in the triclinic space group P1 (No. 2) with a = 12.303(4) A, b = 12.471(4) A, c = 12.541(4) A, alpha = 114.607(8) degrees, beta = 102.547(6) degrees, gamma = 99.889(7) degrees, and Z = 2. The structure consists of (Th2P6S18)(4-) layers separated by layers of cesium cations and only contains the (P2S6)(4-) building block. Compound II crystallizes as red blocks in the triclinic space group P1 (No. 2) with a = 11.531(3) A, b = 12.359(4) A, c = 16.161(5) A, alpha = 87.289(6) degrees, beta = 75.903(6) degrees, gamma = 88.041(6) degrees, and Z = 2. The structure consists of linear chains of (Th2P6Se21)(7-) separated by rubidium cations. Compound II contains both the (PSe4)(3-) and (P2Se6)(4-) building blocks. Both structures may be derived from two known rare earth structures where a rare earth site is replaced by an alkali or actinide metal to form these novel structures. Optical band gap measurements show that compound I has a band gap of 2.8 eV and compound II has a band gap of 2.0 eV. Solid-state Raman spectroscopy of compound I shows the vibrations expected for the (P2S6)(4-) unit. Raman spectroscopy of compound II shows the vibrations expected for both (PSe4)(3-) and (P2Se6)(4-) units. Our work shows the remarkable diversity of the actinide chalcophosphate system and demonstrates the phase space is still ripe to discover new structures.     

Thermodynamic Properties of the MZr2(PO4)3 (M=Na,K, Rb or Cs) Compounds

The enthalpies of the solution of MZr₂(PO₄)₃(M=Na, K, Rb or Cs) compounds have been measured by the help of a differential automatic isothermal Calvet calorimeter and the standard enthalpies of formation have been derived. The temperature dependencies of the standard heat capacity of the samples of crystalline NaZr₂(PO₄)₃ and CsZr₂(PO₄)₃ were studied between 7 and 340 K in an automatic adiabatic vacuum calorimeter. The main thermodynamic functions H ⁰(T)–H ⁰(0), S ⁰(T) andG ⁰(T)–H ⁰(0) have been determined. The Gibbs energies of formation of the NaZr₂(PO₄)₃and CsZr₂(PO₄)₃ at 298.15 K were calculated on the basis of these experimental data and the enthalpy of formation data. Qualitative explanations for the results observed were presented. This revised version was published online in July 2006 with corrections to the Cover Date.