20281-00-9Relevant articles and documents
Electron microscopy, spectroscopy, and first-principles calculations of Cs2O
Gemming,Seifert,Muehle,Jansen,Albu-Yaron,Arad,Tenne
, p. 1190 - 1196 (2005)
Oxides of cesium play a key role in ameliorating the photoelectron emission of various opto-electronic devices. However, due to their extreme reactivity, their electronic and optical properties have hardly been touched upon. With the objective of better understanding the electronic and optical properties of Cs2O in relationship to its structure, an experimental and theoretical study of this compound was undertaken. First-principles density functional theory calculations were performed. The preferred structural motif for this compound was found to be anti-CdCl2. Here three Cs-O-Cs molecular layers are stacked together through relatively weak van-der-Waals forces. The energy bands were also calculated. The lowest transition at 1.45 eV, was found to be between the K point in the valence band to the Γ point in the conduction band. A direct transition at 2 eV was found in the center (Γ) of the Brillouin zone. X-ray powder diffraction, transmission electron microscopy and selected area electron diffraction were used to analyze the synthesized material. These measurements showed good agreement with the calculated structure of this compound. Absorption measurements at 4.2 K indicated two optical transitions with somewhat higher energy (indirect one at 1.65 and a direct transition at 2.2 eV, respectively). Photoluminescence measurements also showed similar transitions, suggesting that the lower indirect transition is enhanced by three nearby minima at 1.5 eV in the Brillouin zone.
The suboxometallates A9MO4 (A = Rb, Cs; M = Al, Ga, In, Fe, Sc)
Hoch, Constantin,Bender, Johannes,Wohlfarth, Andreas,Simon, Arndt
, p. 1777 - 1782 (2009)
Single crystals of the suboxometallates A9MO4 (A = Rb, Cs; M = Al, Ga, Fe, Sc) were prepared by reaction of stoichiometric mixtures of M2O3 with alkali metals and their oxides A 2O. They crystallize i
Alkali Metal Suboxometalates-Structural Chemistry between Salts and Metals
W?rsching, Matthias,Hoch, Constantin
, p. 7058 - 7064 (2015)
The crystal structures of the new cesium-poor alkali metal suboxometalates Cs10MO5 (M = Al, Ga, Fe) show both metallic and ionic bonding following the formal description (Cs+)10(MO45-)(O2-)·3e-. Comparable to the cesium-rich suboxometalates Cs9MO4 (M = Al, Ga, In, Fe, Sc) with ionic subdivision (Cs+)9(MO45-)·4e-, they contain an oxometalate anion [MIIIO4]5- embedded in a metallic matrix of cesium atoms. Columnlike building units form with prevalent ionic bonding inside and metallic bonding on the outer surface. In the cesium-rich suboxometalates Cs9MO4, additional cesium atoms with no contact to any anion are inserted between columns of the formal composition [Cs8MO4]. In the cesium-poor suboxometalates Cs10MO5, the same columns are extended by face-sharing [Cs6O] units, and no additional cesium atoms are present. The terms "cesium-rich" and "cesium-poor" here refer to the Cs:O ratio. The new suboxometalates Cs10MO5 crystallize in two modifications with new structure types. The orthorhombic modification adopts a structure with four formula units per unit cell in space group Pnnm with a = 11.158(3) ?, b = 23.693(15) ?, and c = 12.229(3) ? for Cs10AlO5. The monoclinic modification crystallizes with eight formula units per unit cell in space group C2/c with a = 21.195(3) ?, b = 12.480(1) ?, c = 24.120(4) ?, and β = 98.06(1)° for Cs10AlO5. Limits to phase formation are given by the restriction that the M atoms must be trivalent and by geometric size restrictions for the insertion of [Cs6O] blocks in Cs10MO5. All of the suboxometalate structures show similar structural details and form mixed crystal series with statistical occupation for the M elements following the patterns Cs9(M1xM21-x)O4 and Cs10(M1xM21-x)O5. The suboxometalates are a new example of ordered intergrowth of ionic and metallic structure elements, allowing for the combination of properties related to both ionic and metallic materials. (Figure Presented).
Anomalous lattice parameter increase in alkali earth aluminium substituted tungsten defect pyrochlores
Thorogood, Gordon J.,Kennedy, Brendan J.,Peterson, Vanessa K.,Elcombe, Margaret M.,Kearley, Gordon J.,Hanna, John V.,Luca, Vittorio
, p. 457 - 464 (2009)
The structures of the defect pyrochlores AAl0.33W1.67O6 where A=K, Rb or Cs have been investigated using X-ray and neutron powder diffraction methods as well as the ab initio modelling program VASP. The three cubic pyrochl
Preparation and structural characterization of stable Cs2O closed-cage structures
Albu-Yaron, Ana,Arad, Talmon,Popovitz-Biro, Ronit,Bar-Sadan, Maya,Prior, Yehiam,Jansen, Martin,Tenne, Reshef
, p. 4169 - 4172 (2005)
(Figure Presented) Fullerene-like Cs2O nanoparticles were prepared by laser ablation of 3R-Cs2O powder in evacuated quartz ampoules. The Cs2O closed cages, such as the faceted nanoparticle shown in the picture, are remarka
First isolated hypoelectronic [In6]6- cluster in insulating Cs22In6(SiO4)4
Saltykov, Vyacheslav,Nuss, Juergen,Wedig, Ulrich,Prasad, Dasari L. V. K.,Jansen, Martin
, p. 834 - 839 (2011)
Cs22In6(SiO4)4 was synthesized by the reaction of appropriate starting materials at 673 K, followed by slow cooling to room temperature, in arc-welded tantalum ampoules. According to single-crystal X-ray analysis, the compound crystallizes in a new structure type (P21/n(no. 14), a = 14.3533(4), b = 16.1712(4), c = 25.0135(7) A, β = 94.368(1), Z = 4), consisting of [In6]6- clusters with the shape of a distorted octahedron or more appropriately described as a condensate of three face sharing tetrahedra. The cluster is the first example of a hypoelectronic isolated [In6] 6- indium cluster. The oxosilicate indide can be regarded as a double salt , Cs6In6 on one hand and the oxosilicate Cs4SiO4 (× 4) on the other, which form the quaternary structure by inhomogeneous intergrowth of partial structures. The electronic structure of Cs22In6(SiO4) 4 was examined by DFT calculations and compared to the one of Rb 2In3, which exhibits linked In6 polyhedra. According to the DOS the title compound is a semiconductor with a band gap of 0.5 eV, which is in agreement with its observed insulating character. [In 6]6- is an isolated cluster bearing inert electron pairs at each vertex. In contrast, [In6]4- in Rb2In3 only exhibits inert pairs at the apical atoms. The four basal atoms are linked to neighboring clusters by covalent bonds forming a 2D network. These bonding scenarios are supported by the analysis of the projected density of states, the electron localization function and the partitioning of the electron density according to Bader. Copyright
Cs10Tl6SiO4, Cs10Tl 6GeO4, and Cs10Tl6SnO3 - First oxotetrelate thallides, double salts containing "hypoelectronic" [Tl6]6- clusters
Saltykov, Vyacheslav,Nuss, Juergen,Jansen, Martin
, p. 1163 - 1168 (2011)
Cs10Tl6TtO4 (Tt = Si, Ge) and Cs 10Tl6SnO3 were synthesized by the reaction of appropriate starting materials at 623-673 K, followed by fast cooling or quenching to room temperature, in arc
From ∞1[(UO2)2O(MoO 4)4]6- to ∞ 1[(UO2)2(MoO4)3(MoO 5)]6- infinite chains in A6U2Mo 4O21 (A=Na, K, Rb, Cs) compounds: Synthesis and crystal structure
Yagoubi,Obbade,Saad,Abraham
, p. 971 - 981 (2011)
A new caesium uranyl molybdate belonging to the M6U 2Mo4O21 family has been synthesized by solid-state reaction and its structure determined from single-crystal X-ray diffraction data. Contrary to the other alkali uranyl molybdates of this family (A=Na, K, Rb) where molybdenum atoms adopt only tetrahedral coordination and which can be formulated A6[(UO2)2O(MoO 4)4], the caesium compound Cs6U 2Mo4O21 should be written Cs 6[(UO2)2(MoO4)3(MoO 5)] with molybdenum atoms in tetrahedral and square pyramidal environments. Cs6[(UO2)2(MoO4) 3(MoO5)] crystallizes in the triclinic symmetry with space group P1 and a=10.4275(14) A, b=15.075(2) A, c=17.806(2) A, α=70.72(1)°, β=80.38(1)° and γ=86.39(1)°, V=2604.7(6) A3, Z=4, ρmes=5.02(2) g/cm 3 and ρcal=5.08(3) g/cm3. A full-matrix least-squares refinement on the basis of F2 yielded R 1=0.0464 and wR2=0.0950 for 596 parameters with 6964 independent reflections with I≥2σ(I) collected on a BRUKER AXS diffractometer with Mo(Kα) radiation and a CCD detector. The crystal structure of Cs compound is characterized by ∞ 1[(UO2)2(MoO4)3(MoO 5)]6- parallels chains built from U2O 13 dimeric units, MoO4 tetrahedra and MoO5 square pyramids, whereas, Na, K and Rb compounds are characterized by ∞1[(UO2)2O(MoO 4)4]6- parallel chains formulated simply of U2O13 units and MoO4 tetrahedra. Infrared spectroscopy measurements using powdered samples synthesized by solid-state reaction, confirm the structural results. The thermal stability and the electrical conductivity are also studied. The four compounds decompose at low temperature (between 540 and 610 °C).
Bad-Metal-Layered Sulfide Oxide CsV2S2O
Valldor, Martin,Merz, Patrick,Prots, Yurii,Schnelle, Walter
, p. 23 - 27 (2016/01/15)
Through a solid-state reaction between stoichiometric amounts of a mixed cesium oxide Cs2O1.3, VS, S, and V2O5, a polycrystalline powder of CsV2S2O was obtained. Small single crystals could be grown in a CsCl melt by allowing Cs2SO4, V metal and S powders to react. The crystals have a plate-like morphology, consistent with the tetragonal crystal-structure symmetry [P4/mmm, a = 3.9455(1), c = 7.4785(1) ?]. Magnetic measurements suggest that CsV2S2O is a temperature-independent paramagnet, and resistivity data concur with a bad metal. The mixed oxidation state of V on one crystallographic site offers a tentative explanation of the electronic properties of the title compound. CsV2S2O has a tetragonal crystal structure and contains Cs-separated V-S-O layers with relatively short V-V distances of 2.790 ?. V has formally a charge of +2.5, resulting in temperature-independent paramagnetism and bad-metal-like electric conductivity.
