Exploratory syntheses and structures of SrAu(4.3)In(1.7) and CaAg(3.5)In(1.9): electron-poor intermetallics with diversified polyanionic frameworks that are derived from the CaAu4In2 approximant

The phase regions around quasicrystals and approximants (QC/ACs) are rich pools for electron-poor intermetallics with novel, complex structures, and bonding patterns. The present SrAu(4.30(1))In(1.70(1)) (1) and CaAg(3.54(1))In(1.88(1)) (2) were synthesized through chemical tunings of the model CaAu(4)In(2) (YCd(6)-Type) AC. Single crystal X-ray diffraction analyses reveals that crystal 1 has Pnma (CeCu(6)-type) symmetry, with a = 9.102(1) ?, b = 5.6379(9) ?, and c = 11.515(2) ?. The building block in 1 is a 19-vertex cluster Sr@Au(9)In(4)M(6) (M = Au/In), which vividly mimics Ca@(Au,In)(18) in Ca(3)Au(12.4)In(6.1) (YCd(6)-type) in geometry. These clusters aggregate into one-dimensional columns extending along the b axis. Crystal 2 (P6/mmm, a = 20.660(3) ?, c = 9.410(2) ?) is closely related to Na(26)Cd(141) (hP167) and Y(13)Pd(40)Sn(31) (hP168), which are differentiated by the selective occupation of Wyckoff 1a (0 0 0) or 2d (1/3 2/3 1/2) sites by Cd or Pd. Crystal 2 adopts the Na(26)Cd(141) structure, but the 1a site is split into two partially occupied sites. The synergistic disorder in the hexagonal tunnels along c is a major property. The valence electron count per atom (e/a) values for 1 and 2 are 1.63 and 1.74, respectively, the lowest among any other ternary phases in each system. These values are close to those of ACs in the Ca-Au-M (M = Ga, In) systems. Electronic structures for both are discussed in terms of the results of TB-LMTO-ASA calculations.     

Development of the Ca-Au-In icosahedral Quasicrystal and two crystalline approximants: practice via pseudogap electronic tuning

Electronic tuning and syntheses to gain the icosahedral quasicrystal (i-QC) (Ca14.1(2)Au44.2(8)In41.7(7), e/a = 1.98) and two approximant crystals (ACs) are reported. The tuning was derived from Na2Au6In5, another cubic Mg2Zn11-type structure, for which the Fermi level (e/a = 1.77) should tune to a calculated pseudogap (e/a = 2.02) under a rigid band assumption. The 1/1 AC, Ca3Au12.2(1)In6.3(2) (e/a = 1.73), crystallizes in space group Im, with a = 15.152(2) A, Z = 8, and the 2/1 AC, Ca12.6(1)Au37.0(2)In39.6(6) (e/a = 2.01), in Pa, with a = 24.632(3) A , Z = 8. Both have substantially fixed compositions according to lattice dimensions. Structure analyses reveal that both ACs contain triacontahedral clusters as the basic building blocks at the body-centered and primitive cubic unit cell levels, respectively. Densities-of-states (DOS) analyses for the 1/1 AC structure reveal a pseudogap at e/a = 2.00, close to the point at which the i-QC was predicted and experimentally tuned. Phase relationships of the ACs and the i-QC are reported according to DTA, XRD, and temperature-dependent XRD measurements. The QC is thermodynamically metastable below approximately 500 degrees C.     

Approximant phases and an icosahedral quasicrystal in the Ca-Au-Ga system: the influence of size of gallium versus indium

Two crystalline approximants (ACs) and their corresponding icosahedral quasicrystal (i-QC) are obtained in the Ca-Au-Ga system through conventional solid-state exploratory syntheses. Single crystal structural analyses reveal that the 1/1 AC, Ca 3Au x Ga 19- x ( x = approximately 9.3-12.1) [ Im3, a = 14.6941(6)-14.7594(6) A], has the empty cubes in the prototypic YCd 6 (= Y 3Cd 18) now fully occupied by Ga, resulting in a 3:19 stoichiometry. In parallel, the distorted cubes in the 2/1 AC, Ca 13Au 57.1Ga 23.4 [ Pa3, a = 23.9377(8) A] are fully or fractionally occupied by Ga. The valence electron count per atom ( e/ a) for the 2/1 AC (1.64) is smaller than that over the 1/1 AC composition range (1.76-2.02), and the e/ a of the Ca 15.2Au 50.3Ga 34.5 i-QC, 1.84, is somewhat distant from typical values for Tsai-type i-QCs ( approximately 2.0). Comparisons of the gallium results with the corresponding In phases suggest that the structural differences result mainly from size rather than electronic factors. The 1/1 and 2/1 appear to be thermodynamically stable on slow cooling, as usual, whereas the i-QC isolated by quenching decomposes on heating at approximately 660 degrees C, mainly into 2/1 AC and Ca 3(Au,Ga) 11. Calculations of the electronic structure of 1/1 AC suggest that the Fermi sphere-Brillouin zone interactions remain important for the Ca-Au-Ga i-QC.     

Ca14Au46Sn5: a "colored" Gd14Ag51-type structure containing columns of well-differentiated hexagonal gold stars

A novel hexagonal phase discovered near the Ca(15)Au(60)Sn(25) quasicrystal and its cubic approximants (ACs) was synthesized by means of high-temperature solid-state reactions. Single-crystal structural analyses show that this is a Gd(14)Ag(51) isotype with composition within the range Ca(14)Au(45.56(4)-46.67(4))Sn(5.14(3)-4.14(3)), space group P6/m (No. 175), and lattice parameters a = 12.763(3)-12.879(3) ? and c = 9.326(3)-9.3815(4) ?. In this phase, Sn mixes with Au in two of seven anionic sites to give a strong coloring that generates a narrow honeycomb-like Au/Sn template, in which sizable columns of hexagonal Au stars are confined. This phase transforms into the cubic 2/1 AC phase through a peritectic reaction at ～678 °C. The valence electron count per atom (e/a) of the present phase is in the range 1.41-1.45. However, it does not appear to follow a Hume-Rothery mechanism.     

The 1/1 and 2/1 approximants in the Sc-Mg-Zn quasicrystal system: triacontahedral clusters as fundamental building blocks

Single-crystal structures are reported for Sc(3)Mg(0.18(1))Zn(17.73(3)), the 1/1 approximant crystal (AC), and Sc(11.18(9))Mg(2.5(1))Zn(73.6(2)), the 2/1 AC, in the corresponding icosahedral quasicrystal (i-QC) system. The 1/1 AC crystallizes in space group Im, a = 13.863(2) A, Z = 8, and the 2/1 AC, in Pa, a = 22.412 (2) A, Z = 8. The latter, which is valuable in pointing the way to the QC structure, is the best ordered and refined 2/1 example to date. The fundamental building blocks in both ACs are triacontahedral clusters centered by smaller multiply endohedral Tsai-type arrays; the former are condensed through body-centered-cubic packing in the 1/1 and primitive cubic packing in the 2/1 AC. Novel prolate rhombohedra centered by Sc-Sc dimers are also generated between triacontahedra in the 2/1 AC.     

Conventional and stuffed bergman-type phases in the na-au-T (T = ga, ge, sn) systems: syntheses, structures, coloring of cluster centers, and fermi sphere-brillouin zone interactions

Bergman-type phases in the Na-Au-T (T = Ga, Ge, and Sn) systems were synthesized by solid-state means and structurally characterized by single-crystal X-ray diffraction studies. Two structurally related (1/1) Bergman phases were found in the Na-Au-Ga system: (a) a conventional Bergman-type (CB) structure, Na(26)Au(x)Ga(54-x), which features empty innermost icosahedra, as refined with x = 18.1 (3), Im3?, a = 14.512(2) ?, and Z = 2; (b) a stuffed Bergman-type (SB) structure, Na(26)Au(y)Ga(55-y), which contains Ga-centered innermost icosahedra, as refined with y = 36.0 (1), Im3?, a = 14.597(2) ?, and Z = 2. Although these two subtypes have considerable phase widths along with respective tie lines at Na ≈ 32.5 and 32.1 atom %, they do not merge into a continuous solid solution. Rather, a quasicrystalline phase close to the Au-poor CB phase and an orthorhombic derivative near the Au-rich SB phase lie between them. In contrast, only Au-rich SB phases exist in the Ge and Sn systems, in which the innermost icosahedra are centered by Au rather than Ge or Sn. These were refined for Na(26)Au(40.93(5))Ge(14.07(5)) (Im3?, a = 14.581(2) ?, and Z = 2) and Na(26)Au(39.83(6))Sn(15.17(6)) (Im3?, a = 15.009(2) ?, and Z = 2), respectively. Occupations of the centers of Bergman clusters are rare. Such centering and coloring correlate with the sizes of the neighboring icosahedra, the size ratios between electropositive and electronegative components, and the values of the average valence electron count per atom (e/a). Theoretical calculations revealed that all of these phases are Hume-Rothery phases, with evident pseudogaps in the density of states curves that arise from the interactions between Fermi surface and Brillouin zone boundaries corresponding to a strong diffraction intensity.     

Ca4Au10In3: synthesis, structure, and bonding analysis. The chemical and electronic transformations from the isotypic Zr7Ni10 intermetallic

The title compound, Ca(4)Au(10)In(3) (e/a = 1.59), was synthesized by conventional high-temperature solid-state reactions and structurally analyzed by single-crystal X-ray diffraction: space group Cmca, a = 13.729(4) A, b = 10.050(3) A, c = 10.160(3) A, Z = 4. The structure, isotypic with that of Zr(7)Ni(10), features a novel three-dimensional [Au(10)In(3)] polyanionic framework built from sinusoidal Au layers that are interconnected by significant Au-Au and Au-In interactions. A prominent electronic feature is the presence of a pseudogap and empty bonding states above the Fermi level according to LMTO calculations, reminiscent of the tunable electronic properties discovered for Mg(2)Zn(11)-type phases. The natures of the chemical and electronic redistributions from Zr(7)Ni(10) to Ca(4)Au(10)In(3) are considered. The Au backbone appears to be particularly important.     

Synthesis, structure, and bonding of Eu3Bi(Sn,Bi)4. A rare inverse-Cr5B3-type structure with a new tin/bismuth network

The ternary phase Eu3Bi(Sn1-xBix)4 ( approximately 0 < x < approximately 0.15) has been synthesized by solid-state methods at high temperature. The crystal structure of the limiting Eu3Bi(Sn3.39Bi0.61(3)) has been determined by single-crystal X-ray analysis to be isopointal with an inverse-Cr5B3-type structure [space group I4/mcm, Z = 4, a = 8.826(1) A, c = 12.564(3) A, and V = 978.6(3) A3]. The structure contains slabs of three-bonded Sn/Bi atoms as puckered eight- and four-membered rings interlinked at all vertices, and these are separated by planar layers of individual Eu and Bi atoms. In the normal (stuffed) Cr5B3-type analogue Eu5Sn3Hx, these two units are replaced by a more highly puckered network of Eu cations around isolated Sn atoms and planar layers of isolated Eu atoms and Sn dimers, respectively. Band structures of limiting models of the phase calculated by TB-LMTO-ASA methods show a metallic character and indicate that the mixed Sn/Bi occupancy in the slabs in this structure for x > 0 probably originates with the electronic advantages of the pseudogap that would occur at the electron count of the ideal Zintl phase Eu3Bi(Sn3Bi). The stability of a competing phase reduces this limit to Eu3Bi(Sn3.4Bi0.6).     

Diaminogermylene and diaminostannylene derivatives of gold(I): novel AuM and AuM2 (M = Ge, Sn) complexes

The reactions of [AuCl(THT)] (THT = tetrahydrothiophene) with 1 equiv of the group 14 diaminometalenes M(HMDS)(2) [M = Ge, Sn; HMDS = N(SiMe(3))(2)] lead to [Au{MCl(HMDS)(2)}(THT)] [M = Ge (1), Sn (2)], which contain a metalate(II) ligand that arises from insertion of the corresponding M(HMDS)(2) reagent into the Au-Cl bond of the gold(I) reagent. While compound 1 reacts with more Ge(HMDS)(2) to give the germanate-germylene derivative [Au{GeCl(HMDS)(2)}{Ge(HMDS)(2)}] (3), which results from substitution of Ge(HMDS)(2) for the THT ligand of 1, an analogous treatment of compound 2 with Sn(HMDS)(2) gives the stannate-stannylene derivative [Au{SnCl(HMDS)(2)}{Sn(HMDS)(2)(THT)}] (4), which has a THT ligand attached to the stannylene tin atom and which, in solution at room temperature, participates in a dynamic process that makes its two Sn(HMDS)(2) fragments equivalent (on the NMR time scale). A similar dynamic process has not been observed for the AuGe(2) compound 3 or for the AuSn(2) derivatives [Au{SnR(HMDS)(2)}{Sn(HMDS)(2)(THT)}] [R = Bu (5), HMDS (6)], which have been prepared by treating complex 4 with LiR. The structures of compounds 1 and 3-6 have been determined by X-ray diffraction.     

Comparative study on composition, structure, and adsorption behavior of activated carbons derived from different synthetic waste polymers

The composition, structure, and adsorption behavior of activated carbons (ACs) derived from three different types of waste polymers, i.e., tire rubber (TR), polyvinyl chloride (PVC), and polyethyleneterephtalate (PET), by KOH activation were compared. The AC derived from PET exhibited the largest surface area (2831 m(2)/g) and pore volume (1.68 cm(3)/g) due to the homogenous aromatic composition of PET. The AC derived from PVC exhibited relatively lower surface area (2666 m(2)/g) but more narrowed pore size distribution (2-3 nm). The complex composition and high ash content of tire particles resulted in AC product with significantly lower surface area (398.5 m(2)/g) and heterogeneous pore width. Adsorption data of methylene blue (MB) were fitted well by Langmuir equation, indicating monolayer coverage on the ACs. The high oxygen content of PET-derived AC heavily affected its adsorption to MB and iodine. Due to the remarkable surface area and highly mesoporous structures, ACs based on both PET and PVC exhibited much higher adsorption capacities than that of TR and commercial coal-based AC (F400). This study demonstrates that the properties of ACs are highly dependent on their starting polymers and the potential of converting synthetic polymer waste into effective adsorbents for environmental remediation and cleanup.     

Polar intermetallic compounds as catalysts for hydrogenation reactions: synthesis, structures, bonding, and catalytic properties of Ca(1-x)Sr(x)Ni4Sn2 (x=0.0, 0.5, 1.0) and catalytic properties of Ni3Sn and Ni3Sn2

The potential of polar intermetallic compounds to catalyze hydrogenation reactions was evaluated. The novel compounds CaNi4Sn2, SrNi4Sn2, and Ca(0.5)Sr(0.5)Ni(4)Sn(2) were tested as unsupported alloys in the liquid-phase hydrogenation of citral. Depending on the reaction conditions, conversions of up to 21.0 % (253 K and 9.0 MPa hydrogen pressure) were reached. The binary compounds Ni3Sn and Ni3Sn2 were also tested in citral hydrogenation under the same conditions. These materials gave conversions of up to 37.5 %. The product mixtures contained mainly geraniol, nerol, citronellal, and citronellol. The isotypic stannides CaNi4Sn2, Ca(0.5)Sr(0.5)Ni4Sn2, and SrNi4Sn2 were obtained by melting mixtures of the elements in an arc-furnace under an argon atmosphere. Single crystals were synthesized in tantalum ampoules using special temperature modes. The novel structures were established by single-crystal X-ray diffraction. They crystallize in the tetragonal space group I4/mcm with parameters: a=7.6991(7), c=7.8150(8) A, wR2=0.034, 162 F(2) values, 14 variable parameters for CaNi4Sn2; a=7.7936(2), c=7.7816(3) A, wR2=0.052, 193 F(2) values, 15 variable parameters for Ca(0.5)Sr(0.5)Ni4Sn2; and a=7.8916(4), c=7.7485(5) A, wR2=0.071, 208 F(2) values, 14 variable parameters for SrNi4Sn2. The Ca(1-x)Sr(x)Ni(4)Sn(2) (x=0.0, 0.5, 1.0) structures can be represented as a stuffed variant of the CuAl2 type by the formal insertion of one-dimensional infinite Ni-cluster chains [Ni4] into the Ca(Sr)Sn2 substructure. The Ni and Sn atoms form a three-dimensional infinite [Ni4Sn2] network in which the Ca or Sr atoms fill distorted octagonal channels. The densities of states obtained from TB-LMTO-ASA calculations show metallic character for both compounds.     

Synthesis and structure of [(Sn(mu-PCy))3(Na x PMDETA)2], containing an electron-deficient [(Sn(mu-PCy))3]2- dianion

The reaction of CyPHNa with Sn(NMe2)2 in the presence of PMDETA (= (Me2NCH2CH2)2NMe) gives the title compound [(Sn(mu-PCy))3(Na x PMDETA)2] (1), containing an electron-deficient [(Sn(mu-PCy))]3(2-) dianion with a novel two-electron, three centre (2e-3c) bonding arrangement.     

Theoretical study of electronic structures and spectroscopic properties of Ga3Sn, GaSn3, and their ions

Ground and excited states of mixed gallium stannide tetramers (Ga3Sn, Ga3Sn+, Ga3Sn-, GaSn3, GaSn3+, and GaSn3-) are investigated employing the complete active space self-consistent-field (CASSCF), density function theory (DFT), and the coupled-cluster single and double substitution (including triple excitations) (CCSD(T)) methods. The ground states of Ga3Sn, Ga3Sn+, and Ga3Sn- are found to be the 2A1, 3B1, and 1A1 states in C2v symmetry with a planar quadrilateral geometry, respectively. The ground states of GaSn3 and GaSn3- is predicted to be the 2A1 and 1A1 states in C2v point group with a planar quadrilateral structure, respectively, while the ground state of GaSn3+ is the 1A1 state with ideal triangular pyramid C3v geometry. Equilibrium geometries, vibrational frequencies, binding energies, electron affinities, ionization energies, and other properties of Ga3Sn and GaSn3 are computed and discussed. The anion photoelectron spectra of Ga3Sn- and GaSn3- are also predicted. It is interesting to find that the amount of charge transfer between Ga and Sn2 atoms in the 1A1 state of GaSn3+ greatly increases upon electron ionization from the 2A1 state of GaSn3, which may be caused by large geometry change. On the other hand, the results of the low-lying states of Ga3Sn and GaSn3 are compared with those of Ga3Si and GaSi3.     

M2Ba2Sn6 (m =yb, ca): metallic zintl phases with a novel tin chain substructure

The compounds M2Ba2Sn6 (M = Yb, Ca) have been synthesized by solid-state reactions in welded Ta tubes at high temperature. Their structures were determined by single-crystal X-ray diffraction studies to be orthorhombic; space group Cmca (No. 64); Z = 8; a = 15.871(3), 15.912 (3) A; b = 9.387(2), 9.497(2) A; c = 17.212(3), 17.184(3) A; and V = 2564.3(9), 2597.0(9) A3, respectively. These contain infinite tin chains along constructed from butterflylike 3-bonded Sn tetramers interconnected by pairs of 2-bonded Sn. The chains are further interconnected into corrugated layers by somewhat longer Sn-Sn bonds along c. The compounds with the chains alone would be Zintl phases, but the interchain bonding makes them formally one-electron rich per formula unit. The electronic structures calculated by extended Hückel and TB-LMTO-ASA methods indicate that these compounds are metallic but with a deep pseudogap at the Fermi level. States that bind the extra electrons lie just below EF and involve important Yb(Ca)-Sn contributions. The origin of metallic Zintl phases is briefly discussed.     

活性炭孔径和比表面积对TiO2/AC光催化性能的影响

采用“同步物理-化学活化法”二次活化商品活性炭, 制备不同孔径和比表面积的系列活性炭(AC)载体, 以偏钛酸为钛源, 利用均匀沉淀法制备TiO2负载型光催化剂(TiO2/AC), 用氮吸附、XRD、SEM等方法表征, 研究活性炭的孔径和比表面积对TiO2/AC性能的影响; 并通过降解水溶液中的亚甲基蓝(MB)研究TiO2/AC光催化氧化特性, 考察催化剂投加量、不同MB浓度等因素对光催化氧化的影响. 结果表明, 负载的TiO2粒子粒径为12-20 nm, 活性炭的比表面积大、平均孔径大有利于TiO2的均匀分散, 阻止TiO2晶粒生长, 有利于充分发挥TiO2小尺度效应; 另外, 活性炭吸附和TiO2光解的协同效应使TiO2/AC光催化剂对MB降解的效率显著提高. 动力学研究表明, TiO2/AC光催化降解MB反应符合表观一级动力学特征.     

孔结构对活性炭吸附水溶液中铅离子的影响

选取三种表面化学性质相近的活性炭(AC),通过等温吸附实验考察活性炭对水溶液中铅离子的吸附性能,利用扫描电子显微镜(SEM)观察活性炭的表面微观形貌,通过低温(77 K)液氮吸附测定活性炭的比表面积和孔容,并分别以密度泛函理论(DFT)和Barrett-Joyner-Halenda (BJH)法计算微孔和中孔的孔径分布.结果表明:选用的三种活性炭AC1、AC2、AC3在比表面积和总孔容上呈依次下降的趋势,但表面开放孔均匀分布的AC2,具有最高的饱和吸附量,孔结构类似颗粒堆积孔的AC3,具有与表面开放孔分布集中的AC1相近的饱和吸附量;通过对孔结构与吸附量的关联分析可知,在活性炭吸附铅离子的过程中, 0.4-0.6 nm的孔是有效吸附孔, 10.5-20.6 nm、20.6-55.6 nm、5.2-10.5 nm三个区间的孔则会对吸附产生阻碍作用.     

Adsorption of anionic and cationic dyes by activated carbons, PVA hydrogels, and PVA/AC composite

The textural and adsorption characteristics of a series of activated carbons (ACs), porous poly(vinyl alcohol) (PVA) gels, and PVA/AC composites were studied using scanning electron microscopy, mercury porosimetry, adsorption of nitrogen (at 77.4 K), cationic methylene blue (MB), anionic methyl orange (MO), and Congo red (CR) from the aqueous solutions. Dye-PVA-AC-water interactions were modeled using the semiempirical quantum chemical method PM6. The percentage of dye removed (C(rem)) by the ACs was close to 100% at an equilibrium concentration (C(eq)) of less than 0.1 mM but decreased with increasing dye concentration. This decrease was stronger at C(eq) of less than 1 mM, and C(rem) was less than 50% at a C(eq) of 10-20 mM. For PVA and the PVA/AC composite containing C-7, the C(rem) values were minimal (<75%). The free energy distribution functions (f(ΔG)) for dye adsorption include one to three peaks in the -ΔG range of 1-60 kJ/mol, depending on the dye concentration range used and the spatial, charge symmetry of the hydrated dye ions and the structural characteristics of the adsorbents. The f(ΔG) shape is most complex for MO with the most asymmetrical geometry and charge distribution and adsorbed at concentrations over a large C(eq) range. For symmetrical CR ions, adsorbed over a narrow C(eq) range, the f(ΔG) plot includes mainly one narrow peak. MB has a minimal molecular size at a planar geometry (especially important for effective adsorption in slit-shaped pores) which explains its greater adsorptive capacity over that of MO or CR. Dye adsorption was greatest for ACs with the largest surface area but as molecular size increases adsorption depends to a greater extent on the pore size distribution in addition to total and nanopore surface areas and pore volume.     

Probing the electronic structures of ternary perovskite and pyrochlore oxides containing Sn(4+) or Sb(5+)

Experimental and computational studies were performed to understand the electronic structure of ternary perovskites (ASnO(3), A = Ca, Sr, Ba, Cd), pyrochlores (RE(2)Sn(2)O(7), RE = Y, La, Lu; Cd(2)Sb(2)O(7)), and defect pyrochlore oxides (Ag(2)Sb(2)O(6)) containing the main group ions Sn(4+) and Sb(5+). In all compounds, the lowest energy states in the conduction band arise primarily from the antibonding Sn/Sb 5s-O 2p interaction. In the alkaline-earth stannate perovskites (BaSnO(3), SrSnO(3), and CaSnO(3)) the conduction bandwidth decreases strongly in response to the octahedral tilting distortion triggered by the decreasing size of the alkaline-earth cation. This in turn leads to a corresponding increase in the band gap from 3.1 eV in BaSnO(3) to 4.4 eV in CaSnO(3). The band gap of CdSnO(3) is relatively small (3.0 eV) considering the large octahedral tilting distortion. The origin of this apparent anomaly is the mixing between the empty Cd 5s orbitals and the antibonding Sn 5s-O 2p states. This mixing leads to a widening of the conduction band and a corresponding decrease in the band gap. The participation of the normally inert A-site cation in the electronic structure near the Fermi level can be considered an inductive effect, as it utilizes substitution on the A-site to directly modify the electronic structure of the SnO(3)(2)(-) framework. While the pyrochlore structure is more complicated, the energy level and width of the lowest energy conduction band can be analyzed in a manner similar to that utilized on the perovskite structure. The Sn-O-Sn and Sb-O-Sb bonds are highly distorted from linear geometry in pyrochlore, leading to a relatively narrow conduction band and a wide band gap. In Cd(2)Sb(2)O(7) and Ag(2)Sb(2)O(6) the Cd(2+) and Ag(+) ions exhibit a strong inductive effect that widens the conduction band and lowers the band gap significantly, very similar to the effect observed in the perovskite form of CdSnO(3).     

不同活性焦载体对V2O5/AC催化剂脱硫活性的影响

活性焦载体的选择是制备高活性烟气脱硫催化剂的关键.以四种煤制活性焦(AC)为载体,制得了系列V2O5/AC催化剂.通过脱硫活性评价、催化氧化能力测试和孔结构分析表明,AC表面的高活性氧化位较少,担载V2O5使AC表面产生了新的高活性氧化位,其脱硫活性显著提高;V2O5在具有高比表面积和较大孔容的载体上分散性较好,能够形...     

Ca3Pt(4+x)Ge(13-y) and Yb3Pt4Ge13: new derivatives of the Pr3Rh4Sn13 structure type

The new phases Ca(3)Pt(4+x)Ge(13-y) (x = 0.1; y = 0.4; space group I2(1)3; a = 18.0578(1) ?; R(I) = 0.063; R(P) = 0.083) and Yb(3)Pt(4)Ge(13) (space group P4(2)cm; a = 12.7479(1) ?; c = 9.0009(1) ?; R(I) = 0.061, R(P) = 0.117) are obtained by high-pressure, high-temperature synthesis and crystallize in new distortion variants of the Pr(3)Rh(4)Sn(13) type. Yb(3)Pt(4)Ge(13) features Yb in a temperature-independent non-magnetic 4f(14) (Yb(2+)) configuration validated by X-ray absorption spectra and resonant inelastic X-ray scattering data. Ca(3)Pt(4+x)Ge(13-y) is diamagnetic (χ(0) = -5.05 × 10(-6) emu mol(-1)). The Sommerfeld coefficient γ = 4.4 mJ mol(-1) K(-2) for Ca(3)Pt(4+x)Ge(13-y), indicates metallic properties with a low density of states at the Fermi level in good agreement with electronic structure calculation (N(E(F)) = 3.3 eV(-1)/f.u.)); the Debye temperature (θ(D)) is 398 K.