A new chalcogenide homologous series A2[M(5+n)Se(9+n)] (A = Rb, Cs; M = Bi, Ag, Cd)

The ternary and quaternary selenides, beta-CsBi3Se5, Rb2CdBi6Se11, CsAg(0.5)Bi(3.5)Se6, CsCdBi3Se6, Rb2Ag(1.5)Bi(7.5)Se13, and Cs2Ag(1.5)Bi(7.5)Se13, are all members of the new homologous series A2[M(5+n)Se(9+n)] and crystallize in structures related to each other in a systematic way; these compounds are mid gap semiconductors and are of interest as thermoelectric materials.     

Tropochemical cell-twinning in the new quaternary bismuth selenides KxSn(6-2x)Bi(2+x)Se9 and KSn5Bi5Se13

The quaternary K(x)Sn(6-2x)Bi(2+x)Se(9) and KSn(5)Bi(5)Se(13) were discovered from reactions involving K(2)Se, Bi(2)Se(3), Sn, and Se. The single crystal structures reveal that K(x)Sn(6-2x)Bi(2+x)Se(9) is isostructural to the mineral heyrovskyite, Pb(6)Bi(2)S(9), crystallizing in the space group Cmcm with a = 4.2096(4) A, b = 14.006(1) A, and c = 32.451(3) A while KSn(5)Bi(5)Se(13) adopts a novel monoclinic structure type (C2/m, a = 13.879(4) A, b = 4.205(1) A, c = 23.363(6) A, beta = 99.012(4) degrees ). These compounds formally belong to the lillianite homologous series xPbS.Bi(2)S(3), whose characteristic is derivation of the structure by tropochemical cell-twinning on the (311) plane of the NaCl-type lattice with a mirror as twin operation. The structures of K(x)Sn(6-2x)Bi(2+x)Se(9) and KSn(5)Bi(5)Se(13) differ in the width of the NaCl-type slabs that form the three-dimensional arrangement. While cell-twinning of 7 octahedra wide slabs results in the heyrovskyite structure, 4 and 5 octahedra wide slabs alternate in the structure of KSn(5)Bi(5)Se(13). In both structures, the Bi and Sn atoms are extensively disordered over the metal sites. Some physicochemical properties of K(x)Sn(6-2x)Bi(2+x)Se(9) and KSn(5)Bi(5)Se(13) are reported.     

Novel quaternary lanthanum bismuth sulfides Pb(2)La(x)Bi(8-x)(S(14)), Sr(2)La(x)Bi(8-x)S(14), and Cs(2)La(x)Bi(10-x)S(16) with complex structures

The compounds Pb(2)La(x)Bi(8-x)S(14) (I), Sr(2)La(x)Bi(8-x)S(14) (II), and Cs(2)La(x)Bi(10-x)S(16) (III) were synthesized from the corresponding elements or binary sulfides at temperatures above 850 degrees C. Compounds I and II are isostructural, forming a new structure type, while the structure of III is related to the structure of the mineral kobellite. All compounds crystallize in the orthorhombic space group Pnma (No. 62) with a = 21.2592(4) A, b = 4.0418(1) A, c = 28.1718(3) A, Z = 4 for I, a = 21.190(1) A, b = 4.0417(2) A, c = 28.285(2) A, Z = 4 for II and a = 34.893(4) A, b = 4.0697(4) A, c = 21.508(2) A, Z = 4 for III. All compounds exhibit mixed site occupancy between Bi and La. Furthermore, I and II exhibit disorder between the divalent atom (Sr or Pb) and/or La and/or Bi. The structures of I and II consist of thin walls made of two metal-atom-thick NaCl-type blocks running in two opposite directions in the ac plane, forming rhombus-shaped tunnels. These tunnels are filled with Bi(2)Te(3)-type fragments. In the points where the walls intersect they form Gd(2)S(3)-type fragments. The structure of III consists of a complex three-dimensional framework with Cs-filled tunnels. All compounds are semiconductors with band gaps around 1.0 eV, and they melt around 740-860 degrees C.     

Cs1-xSn1-xBi9+Se15 and Cs1.5-3xBi9.5+xSe15: members of the homologous superseries Am[M1+lSe2+l]2m[M1 + 2l+nSe3 + 3l+n] (A = alkali metal,M = Sn and Bi) allowing structural evolution in three different dimensions

Cs1-xSn1-xBi9+xSe15 and Cs1.5-3xBi9.5+xSe15 crystallize in a new structure type which does not belong to but is closely related to the members of the homologous series Am[M6-Se8]m[M5+nSe9+n]; the new phases reveal a third dimension of structural evolution for this series according to the formula Am[M1+lSe2+l]2m[M1 + 2l + nSe3 + 3l+n].     

New quaternary bismuth sulfides: syntheses,structures, and band structures of AMBiS4 (A = Rb,Cs; M = Si,Ge)

Four new compounds, RbSiBiS(4), RbGeBiS(4), CsSiBiS(4), and CsGeBiS(4), have been synthesized by means of the reactive flux method. The isostructural compounds RbSiBiS(4), RbGeBiS(4), and CsGeBiS(4) crystallize in space group P2(1)/c of the monoclinic system with four formula units in cells of dimensions at 153 K of a = 6.4714(4) A, b = 6.7999(4) A, c = 17.9058(11) A, and beta = 108.856(1) degrees for RbSiBiS(4), a = 6.5864(4) A, b = 6.8559(4) A, c = 17.9810(12) A, and beta = 109.075(1) degrees for RbGeBiS(4), and a = 6.5474(4) A, b = 6.9282(4) A, c = 18.8875(11) A, and beta = 110.173(1) degrees for CsGeBiS(4). CsSiBiS(4) crystallizes in a different structure type in space group P2(1)/c of the monoclinic system with four formula units in a cell of dimensions at 153 K of a = 9.3351(7) A, b = 6.9313(5) A, c = 12.8115(10) A, and beta = 109.096(1) degrees. The two structure types are closely related and consist of [MBiS(4)(-)] (M = Si, Ge) layers separated by bicapped trigonal-prismatically coordinated alkali-metal atoms. In each, the M atom is coordinated to a tetrahedron of four S atoms and the Bi atom is coordinated to seven S atoms comprising five close S atoms at the corners of a square pyramid with Bi near the center of the basal plane and the sixth and seventh S atoms further away to complete a distorted monocapped trigonal prism. The optical band gaps of 2.23 eV for RbGeBiS(4) and 2.28 eV for CsGeBiS(4) were deduced from their diffuse reflectance spectra. From a band structure calculation, the optical absorption for RbGeBiS(4) originates from the [GeBiS(4)(-)] layer. The Ge 4p orbitals, Bi 6p orbitals, and S 3p orbitals are highly hybridized.     

Infrared spectra of the M(NO)n (M = Sn, Pb; n = 1, 2) and PbNO- molecules

Reactions of laser-ablated tin and lead atoms with nitric oxide molecules in solid argon and neon have been investigated using matrix-isolation infrared spectroscopy. In the argon experiments, absorptions at 1560.1, 1625.8, and 1486.7 cm(-1) are assigned to the N-O stretching vibrations of the SnNO and Sn(NO)2 molecules, and absorptions at 1541.9, 1630.0, 1481.8, and 1457.5 cm(-1) are assigned to the N-O stretching vibrations of the PbNO, Pb(NO)2, and PbNO- molecules on the basis of isotopic shifts and splitting patterns. The present neon experiments only produce neutral tin and lead mononitrosyls. Density functional theory calculations have been performed on these tin and lead nitrosyls. The good agreement between the experimental and calculated vibrational frequencies, relative absorption intensities, and isotopic shifts substantiates the identification of these nitrosyls from the matrix infrared spectra.     

碱金属硒化物MHgSbSe~3(M=K,Rb, Cs)的晶体结构及其半导体性 质的研究

用有机溶剂热生长技术(SolvothermalTechnique)制备碱金属硒化物MHgSbSe~3(M=K,Rb,Cs),用单晶X射线衍射技术对其进行晶体结构分析,热分析结果表明,在常温(<200℃)下均为稳定的化合物。光学性质测试表明它们是半导体材料,KHgSbSe~3,RbHgSbSe~3,CsHgSbSe~3的禁带宽度依次为1.85eV,1.75eV,1.65eV。     

Chemical Manipulation of Magnetic Ordering in Mn(1-x)Sn(x)Bi(2)Se(4) Solid-Solutions

Several compositions of manganese-tin-bismuth selenide solid-solution series, Mn(1-x)Sn(x)Bi(2)Se(4) (x = 0, 0.3, 0.75), were synthesized by combining high purity elements in the desired ratio at moderate temperatures. X-ray single crystal studies of a Mn-rich composition (x = 0) and a Mn-poor phase (x = 0.75) at 100 and 300 K revealed that the compounds crystallize isostructurally in the monoclinic space group C2/m (no.12) and adopt the MnSb(2)Se(4) structure type. Direct current (DC) magnetic susceptibility measurements in the temperature range from 2 to 300 K indicated that the dominant magnetic ordering within the Mn(1-x)Sn(x)Bi(2)Se(4) solid-solutions below 50 K switches from antiferromagnetic (AFM) for MnBi(2)Se(4) (x = 0), to ferromagnetic (FM) for Mn(0.7)Sn(0.3)Bi(2)Se(4) (x = 0.3), and finally to paramagnetic (PM) for Mn(0.25)Sn(0.75)Bi(2)Se(4) (x = 0.75). We show that this striking variation in the nature of magnetic ordering within the Mn(1-x)Sn(x)Bi(2)Se(4) solid-solution series can be rationalized by taking into account: (1) changes in the distribution of magnetic centers within the structure arising from the Mn to Sn substitutions, (2) the contributions of spin-polarized free charge carriers resulting from the intermixing of Mn and Sn within the same crystallographic site, and (3) a possible long-range ordering of Mn and Sn atoms within individual {M}(n)Se(4n+2) single chain leading to quasi isolated {MnSe(6)} octahedra spaced by nonmagnetic {SnSe(6)} octahedra.     

M(3-x)(NH4)(x)CrO8 (M = Na, K, Rb, Cs): a new family of Cr5+-based magnetic ferroelectrics

Upon consideration of the hydrogen-bonding properties of the NH(4)(+) cation, we synthesized a new class of compounds, M(3-x)(NH(4))(x)CrO(8) (M = Na, K, Rb, Cs). These magnetic compounds with the simple 3d(1) ground state become ferroelectric. X-ray studies confirmed that the phase transition involves a symmetry change from I42m to Cmc2(1) to P1. The transition temperature depends linearly on the composition variable x. The transitions are of the order-disorder type, with N-H···O bonding playing the central role in the mechanism. Extension of this idea to the introduction of ferroelectricity in several other classes of materials is suggested.     

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.     

Density-functional study of small neutral and cationic bismuth clusters Bi(n) and Bi(n) (+)(n=2-24)

Density-functional theory with scalar-relativistic pseudopotential and a generalized gradient correction is used to calculate the neutral and cationic Bi(n) clusters (2< or =n< or =24), with the aim to elucidate their structural evolution, relative stability, and magnetic property. The structures of neutral Bi clusters are found to be similar to that of other group-V elemental clusters, with the extensively studied sizes of n=4 and 8 having a tetrahedron and wedgelike structure, respectively. Generally, larger Bi clusters consist of a combination of several stable units of Bi(4), Bi(6), and Bi(8), and they have a tendency to form an amorphous structure with the increase of cluster sizes. The curves of second order energy difference exhibit strong odd-even alternations for both neutral and cationic Bi clusters, indicating that even-atom (odd-atom) sizes are relatively stable in neutral clusters (cationic clusters). The calculated magnetic moments are 1micro (B) for odd-atom clusters and zero for even-atom clusters. We propose that the difference in magnetism between experiment and theory can be greatly improved by considering the orbital contribution. The calculated fragmentation behavior agrees well with the experiment, and for each cationic cluster the dissociation into Bi(4) or Bi(7) (+) subclusters confirms the special stability of Bi(4) and Bi(7) (+). Moreover, the bond orders and the gaps between the highest occupied molecular orbital and the lowest unoccupied molecular orbital show that small Bi clusters would prefer semiconductor characters to metallicity.     

Hydrothermal synthesis, thermal, and magnetic data on new alkaline vanadium phosphate My(VO)9 + x(PO4)4x(HPO4)12 - 4x with M = Cs+ (y = 5.29, x = 1) and M = NH4+, Rb+ (y approximately 5, x approximately 1)

Brownish platelet crystals of My(VO)9 + x(PO4)4x(HPO4)12 - 4x (M = Cs+, NH4+ and Rb+) were prepared hydrothermally. The structure of Cs approximately 5(VO)10(PO4)4(HPO4)8 was solved from single-crystal X-ray diffraction data in the centrosymmetric monoclinic space group C2/c (No. 15) a = 21.1951(8) A, b = 12.2051(4) A, c = 20.6230(8) A, beta = 109.742(2) degrees, Z = 4 (R1(Fo) = 0.054, wR2(Fo2) = 0.123). The structure of Cs approximately 5(VO)10(PO4)4(HPO4)8 is described and compared to that of K2(VO)3(HPO4)4 previously reported by Lii. For the three compounds, thermogravimetric data and susceptibility measurements were investigated and were found to be in agreement with the structural study.     

Dimensions of the Ozonide Anion in M([18]crown‐6)O3·x NH3 with M = K (x = 2), Rb (x = 1) and Cs (x = 8)

Reaction of alkali metal ozonides (KO₃, RbO₃ and CsO₃) with [18]crown‐6 in liquid ammonia yields compounds of the composition M([18]crown‐6)O₃·x NH₃ with M = K (x = 2), Rb (x = 1) and Cs (x = 8). The large intermolecular distance between adjacent radical anions in these compounds leads to almost ideal paramagnetic behavior according to Curie's law. Discrepancies concerning the structure of the ozonide anions in the K and Cs compound compared to a former investigation on Rb([18]crown‐6)O₃·NH₃ have been resolved by means of DFT calculations and a single‐crystal structure redetermination.     

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.     

CsMBi(3)Te(6) and CsM(2)Bi(3)Te(7) (M = Pb, Sn): new thermoelectric compounds with low-dimensional structures

The new materials CsPbBi(3)Te(6) and CsPb(2)Bi(3)Te(7) were discovered through reactions of CsBi(4)Te(6) with PbTe, whereas the isostructural materials CsSnBi(3)Te(6) and CsSn(2)Bi(3)Te(7) were discovered through corresponding reactions with SnTe. The compounds can also be prepared from stoichiometric mixtures of Cs(2)Te, Pb (Sn), Bi, and Te. The crystal structures show a layered architecture of NaCl-type slabs alternating with layers of Cs atoms. This group of compounds offers a new quaternary system, Cs-M-Bi-Te (M = Pb and Sn), available for thermoelectric investigations, including fine-tuning of compositions and doping.     

APdCu(Se2)(Se3) (A = K and Rb): new quaternary copper palladium polyselenides with unusual metal-selenium coordination

Two novel metal polyselenides, KPdCu(Se(2))(Se(3)) (I) and RbPdCu(Se(2))(Se(3)) (II), have been synthesized from solvothermal reactions in superheated ethylenediamine at 160 degrees C. The isostructural compounds crystallize in the monoclinic space group P2(1)/m, Z = 2, with a = 6.145(1) A, b = 7.268(1) A, c = 8.865(2) A, beta = 102.41(3) degrees for I, and a = 6.253(1) A, b = 7.267(1) A, c = 8.993(2) A, beta = 102.28(3) degrees for II. Their crystal structures are two-dimensional networks with [PdCu(Se(2))(Se(3))](-) anionic layers built from one-dimensional [Pd(Se(2))(Se(3))](2)(-) "chains" that are "stitched" together by tetrahedrally coordinated Cu atoms. The DSC data show that I and II are stable up to 400 degrees C and decompose at ca. 436 and 424 degrees C, respectively. Both compounds are narrow band-gap semiconductors with estimated band gaps of about 0.7 eV (I) and 0.8 eV (II), respectively. They are the first structurally characterized quaternary copper palladium polychalcogenides with a (Se(2))(2)(-) and a (Se(3))(2)(-) fragment, both exhibiting interesting and unusual metal-selenium coordination.     

Reactions between M+ (M = Si,Ge, Sn and Pb) and benzene in the gas phase

Using a laser ablation/inert buffer gas ion source coupled with a reflectron time-of-flight mass spectrometer, the gas-phase reactions between the IVA group element ions M(+) (M = Si, Ge, Sn and Pb) and benzene seeded in argon gas were studied. In addition to the association reaction pathway (forming [M(C(6)H(6))(x)](+), x = 1, 2, etc.), benzene was dissociated to form complex ions [M(C(5)H(5))](+), [M(C(7)H(5))](+) and [M(C(9)H(x))](+) (x = 5, 7 and 9), etc. DFT theoretical calculations indicated that, in the association products [M(C(6)H(6))](+), the M atom is close to one carbon atom of benzene, while in most of the dissociation complexes, pentagonal structures (M/cyclopentadienyl derivatives) were formed, with the M atom situated near the fivefold axis of the five-membered ring. The bond patterns in these complexes are discussed.     

Structural and thermochemical chemisorption of CO2 on Li(4+x)(Si(1-x)Al(x))O4 and Li(4-x)(Si(1-x)V(x))O4 solid solutions

Different Li(4)SiO(4) solid solutions containing aluminum (Li(4+x)(Si(1-x)Al(x))O(4)) or vanadium (Li(4-x)(Si(1-x)V(x))O(4)) were prepared by solid state reactions. Samples were characterized by X-ray diffraction and solid state nuclear magnetic resonance. Then, samples were tested as CO(2) captors. Characterization results show that both, aluminum and vanadium ions, occupy silicon sites into the Li(4)SiO(4) lattice. Thus, the dissolution of aluminum is compensated by Li(1+) interstitials, while the dissolution of vanadium leads to lithium vacancies formation. Finally, the CO(2) capture evaluation shows that the aluminum presence into the Li(4)SiO(4) structure highly improves the CO(2) chemisorption, and on the contrary, vanadium addition inhibits it. The differences observed between the CO(2) chemisorption processes are mainly correlated to the different lithium secondary phases produced in each case and their corresponding diffusion properties.     

Synthesis and structural characterization of a new series of vanadoselenites, [Se(x)V(4-x)O(12-x)](4-x)- (x=1,2)

Two new vanadoselenites, [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-), were synthesized by reacting SeO(2) with VO(3)(-). Single-crystal X-ray structural analyses of [(n-C(4)H(9))(4)N](3)[SeV(3)O(11)].0.5H(2)O [orthorhombic, space group P2(1)2(1)2, a = 22.328(5) A, b = 44.099(9) A, c = 12.287(3) A, Z = 8] and [[(C(6)H(5))(3)P](2)N](2)[Se(2)V(2)O(10)] [monoclinic, space group P2(1)/n, a = 12.2931(3) A, b = 13.5101(3) A, c = 20.9793(5) A, beta = 106.307(1) degrees, Z = 2] revealed that both anions are composed of Se(x)()V(4)(-)(x)()O(4) rings. The (51)V, (77)Se, and (17)O NMR spectra established that both [SeV(3)O(11)](3)(-) and [Se(2)V(2)O(10)](2)(-) anions maintain this ring structure in solution.     

Electronic structure similarities in Pb(x)Sb(y)(-) and Sn(x)Bi(y)(-) clusters

The geometric and electronic structure of Pb(x)Sb(y)(-) and Sn(x)Bi(y)(-) clusters are investigated by photoelectron spectroscopy and theoretical methods. It is found that PbSb(2)(-) and SnBi(2)(-) have similar spectroscopic patterns, reflecting correlations in electronic nature that are a result of their isoelectronic character and common geometries. Analogous findings are presented for Pb(2)Sb(2)(-) and Sn(2)Bi(2)(-). Further, we investigate the effect of altering the total valence count, and separately the geometry, on spectroscopic patterns. We conclude that these heavy p-block elements are interchangeable and that the electronic structure correspondence can be preserved regardless of elemental composition. This represents an extension of the traditional concepts of periodicity, where elements of similar valence configuration are grouped into columns. Instead, elements from different columns may be combined to yield similarities in chemistry, given the overall valence count is preserved.