The electronic structure of FeO 4 2− , RuO4, RuO 4 − , RuO 4 2− and OsO4 by the HFS-DVM method

The electronic structures of FeO ₄ ^2? , RuO₄, RuO ₄ ^? , RuO ₄ ^2? and OsO₄ have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals is 2t ₂, 1e, 2a ₁, 3t ₂ andt ₁ with thet ₁ orbital as the highest occupied. The first five charge transfer bands are assigned as:t ₁→2e(v ₁), 3t ₂→2e(v ₂),t ₁→4t ₂(v ₃), 3t ₂→4t ₂(v ₄) and 2a ₁→4t ₂(v ₅). It is suggested that ad-d transition should be observed at 1.5 eV in RuO ₄ ^? and RuO ₄ ^2? .     

Nuclear magnetic resonance for differentiating two inequivalent M sites in double anhydrous M2CuCl4 (M = K,Cs, and NH4) single crystals

Nuclear magnetic resonance (NMR) spectra and the spin-lattice relaxation times (T₁) for the M nuclei (M = K, Cs, and NH₄) in M₂CuCl₄ crystals were studied as functions of temperature. The K₂CuCl₄, Cs₂CuCl₄, and (NH₄)₂CuCl₄ single crystals all have the same M₂BX₄ structure, and their two inequivalent sites M(1) and M(2) were differentiated using the NMR results. Because M(2) is surrounded by fewer but closer Cl ligands than M(1), it has a shorter T₁ value than M(1). However, the three crystals have different T₁ temperature dependences and dynamic properties. The rotational tumbling motion defined by the Bloembergen-Purcell-Pound theory was found to occur in (NH₄)₂CuCl₄, but not in K₂CuCl₄ or Cs₂CuCl₄. The differences observed in the spin-lattice relaxation times of the M nuclei may be related to their ionic masses.     

Li+ ion conductivity in the system Li4SiO4Li3VO4

Two ranges of solid solutions were prepared in the system Li₄SiO₄Li₃VO₄: Li_4?xSi_1?xV_xO₄, 0 < x ? 0.37 with the Li₄SiO₄ structure and Li_3+yV_1?ySi_yO₄, 0.18 ? y ? 0.53 with a γ structure. The conductivity of both solid solutions is much higher than that of the end members and passes through a maximum at ～40Li₄SiO₄ · 60Li₃VO₄ with values of ～1 × 10^?5 ohm^?1 cm^?1 at 20°C, rising to ～4 × 10^?2 ohm^?1 cm^?1 at 300°C. These conductivities are several times higher than in the corresponding Li₄SiO₄Li₃(P,As)O₄ systems, especially at room temperature. The solid solutions are easy to prepare, are stable in air, and maintain their conductivity with time. The mechanism of conduction is discussed in terms of the random-walk equation for conductivity and the significance of the term c(1 ? c) in the preexponential factor is assessed. Data for the three systems Li₄SiO₄Li₃YO₄ (Y = P, As. V) are compared.     

Phase formation in the system involving silver, magnesium, and indium molybdates

The subsolidus region of the Ag₂MoO₄-MgMoO₄-In₂(MoO₄)₃ ternary salt system has been studied by X-ray powder diffraction. The formation of new compounds Ag_{1 ? x} Mg_{1 ? x} In_{1 + x} (MoO₄)₃ (0 ≤ x ≤ 0.6) and AgMg₃In(MoO₄)₅ has been established. The unit cell parameters of solid-solution samples have been determined. The Ag_{1 ? x} Mg_{1 ? x} In_{1 + x} (MoO₄)₃ phase of variable composition has a NASICON-type structure (space group R $ \bar 3 $ c) AgMg₃In(MoO₄)₅ is isostructural to sodium magnesium indium molybdate of the same formula unit and crystallizes in triclinic system (space group P $ \bar 1 $ , Z = 2) with the following unit cell parameters: a = 7.0374(5) Å, b = 17.932(1) Å, c = 6.9822(4) Å, α = 87.309(6)°, β = 100.832(6)°, γ = 92.358(6)°. The compounds Ag_{1 ? x} Mg_{1 ? x} In_{1 + x} (MoO₄)₃ and AgMg3In(MoO₄)₅ are thermally stable up to 960 and 1030°C, respectively.     

Synthesis and solution properties of sulfate-type hybrid surfactants with a benzene ring

Nine novel sulfate-type hybrid surfactants, C_mF_2m+1C₆H₄CH(OSO₃Na)C_nH_2n+1 (FmPHnOS: m=4, 6, 8; n=3, 5, 7; C₆H₄: p-phenylene), with a benzene ring in their molecules were synthesized. Alkanoyl chlorides were allowed to react with iodobenzene in the presence of aluminum chloride to give the corresponding aromatic ketones. The reaction of the ketones with perfluoroalkyl iodides yielded 1-[4-(perfluoroalkyl)phenyl]-1-alkanones as intermediates. The intermediates were allowed to react with methanol in tetrahydrofuran in the presence of sodium borohydride to yield 1-[4-(perfluoroalkyl)phenyl]-1-alkanols. The desired hybrid surfactants were obtained by the reaction of 1-[4-(perfluoroalkyl)phenyl-1-alkanols with sulfur trioxide/pyridine complex in pyridine and by the subsequent neutralization of the products with sodium hydroxide solution. When compared with the conventional hybrid surfactants, C_mF_2m+1C₆H₄COCH(SO₃Na)C_nH_2n+1 (FmHnS: m=4, 6; n=2, 4, 6; C₆H₄: p-phenylene), the new hybrid surfactants thus synthesized were found to have a comparable ability to lower the surface tension of water and a high hydrophilicity. The cmc of FmPHnOS obeyed Kleven’s rule and their occupied areas per molecule increased with increasing m and n with the values between 0.66 and 1.05 nm². The aggregation number for FmPHnOS micelles ranged from 6 to 45 and the hydrodynamic radius of the micelles was in the range of 1.4-3.1 nm.     

Defects and Luminescence Behavior of Cubic F23 [(NH4(18-Crown-6))4MnX4] [TlX4]2 (X=Cl, Br) Crystals

Luminescence from [(NH₄(18-Crown-6))₄MnBr₄][TlBr₄]₂ (1), [(NH₄(18-Crown-6))₄MnCl₄][TlCl₄]₂ (2), [(NH₄(18-Crown-6))₂MnBr₄] (3), and [(NH₄(18-Crown-6))₂MnCl₄] (4) was studied in search of new insights regarding crystal defects in 2. Emission from 3 and 4 is normal Mn²⁺(⁴T₁(⁴G)→⁶A₁); that of 2 (λ_max≈520 nm at ca. 300 K and 560 nm at 77 K) is unusual and temperature dependent. Thermal barriers (kJ/mol, assignment): green emission of 1 and 2, T<150 K (1-2, NH⁺₄ rotations), 150<T<250 K (7-14, energy migration among [MnX₄]²⁻), 250<T<300 K (26-35, rotations of 18-Crown-6)); yellow emission of 2: T;<250 K (7-8, energy migration among [MnX₄]²⁻), T>250 K (29 kJ/mol, defect-to-Mn²⁺(⁴T₁(⁴G)) back energy transfer). Crystal data for 4: Space group P2₁/c; Z=4; a=20.173(1) Å; b=9.0144(8) Å; c=20.821(1) Å; β=98.782(5)°; V=3741.9(8) ų; R_w=0.059; R=0.054.     

Synthesis of New Lithium Ionic Conductor Thio-LISICON—Lithium Silicon Sulfides System

The new lithium ionic conductors, thio-LISICON (LIthium SuperIonic CONductor), were found in the ternary Li₂S-SiS₂-Al₂S₃ and Li₂S-SiS₂-P₂S₅ systems. Their structures of new materials, Li_4+xSi_1−xAl_xS₄ and Li_4−xSi_1−xP_xS₄ were determined by X-ray Rietveld analysis, and the electric and electrochemical properties were studied by electronic conductivity, ac conductivity and cyclic voltammogram measurements. The structure of the host material, Li₄SiS₄ is related to the γ-Li₃PO₄-type structure, and when the Li⁺ interstitials or Li⁺ vacancies were created by the partial substitutions of Al³⁺ or P⁵⁺ for Si⁴⁺, large increases in conductivity occur. The solid solution member x=0.6 in Li_4−xSi_1−xP_xS₄ showed high conductivity of 6.4×10^-4 S cm⁻¹ at 27°C with negligible electronic conductivity. The new solid solution, Li_4−xSi_1−xP_xS₄, also has high electrochemical stability up to ∼5 V vs Li at room temperature. All-solid-state lithium cells were investigated using the Li_3.4Si_0.4P_0.6S₄ electrolyte, LiCoO₂ cathode and In anode.     

New three-dimensional inorganic frameworks based on the uranophane-type sheet in monoamine templated uranyl-vanadates

Seven new uranyl vanadates with mono-protonated amine or tetramethylammonium used as structure directing cations, (C₂NH₈)₂{[(UO₂)(H₂O)][(UO₂)(VO₄)]₄}·H₂O (DMetU5V4) (C₂NH₈){[(UO₂)(H₂O)₂][(UO₂)(VO₄)]₃}·H₂O (DMetU4V3), (C₅NH₆)₂{[(UO₂)(H₂O)][(UO₂)(VO₄)]₄}·H₂O (PyrU5V4), (C₃NH₁₀){[(UO₂)(H₂O)₂][(UO₂)(VO₄)]₃}·H₂O (isoPrU4V3), (N(CH₃)₄){[(UO₂)(H₂O)₂][(UO₂)(VO₄)]₃}·H₂O (TMetU4V3), (C₆NH₁₄){[(UO₂)(H₂O)₂][(UO₂)(VO₄)]₃}·H₂O (CHexU4V3), and (C₄NH₁₂){[(UO₂)(H₂O)][(UO₂)(VO₄)]₃} (TButU4V3) were prepared from mild-hydrothermal reactions using dimethylamine, pyridine, isopropylamine, tetramethylammonium hydroxide, cyclohexylamine and tertiobutylamine, respectively, with uranyl nitrate and vanadium oxide in acidic medium. The structures were solved using single-crystal X-ray diffraction data. The compounds exhibit three-dimensional uranyl-vanadate inorganic frameworks built from uranophane-type uranyl-vanadate layers pillared by uranyl polyhedra with cavities in between occupied by protonated organic moieties. In the uranyl-vanadate layers the orientations of the vanadate tetrahedra give new geometrical isomers leading to unprecedented pillared systems and new inorganic frameworks with U/V=4/3. Crystallographic data: (DMetU5V4) orthorhombic, Cmc2₁ space group, a=15.6276(4), b=14.1341(4), c=13.6040(4) Å; (DMetU4V3) monoclinic, P2₁/n space group, a=10.2312(4), b=13.5661(7), c=17.5291(7) Å, β=96.966(2); (PyrU5V4), triclinic, P1 space group, a=9.6981(3), b=9.9966(2), c=10.5523(2) Å, α=117.194(1), β=113.551(1), γ=92.216(1)°; (isoPrU4V3) monoclinic, P2₁/n space group, a=10.3507(1), b=13.6500(2), c=17.3035(2) Å, β=97.551(1)°; (TMetU4V3) orthorhombic, Pbca space group, a=17.1819(2), b=13.6931(1), c=21.4826(2) Å; (CHexU4V3), triclinic P−1 space group, a=9.8273(6), b=11.0294(7), c=12.7506(8) Å, α=98.461(3), β=96.437(3), γ=105.955(3)°; (TButU4V3), monoclinic, P2₁/m space group, a=9.8048(4), b=17.4567(8), c=15.4820(6) Å, β=106.103(2).     

Structural change in a series of protonated layered perovskite compounds, HLnTiO4 (Ln=La, Nd and Y)

A deuterated n=1 Ruddlesden-Popper compound, DLnTiO₄ (HLnTiO₄, Ln=La, Nd and Y), was prepared by an ion-exchange reaction of Na⁺ ions in NaLnTiO₄ with D⁺ ions, and its structure was analyzed by Rietveld method using powder neutron diffraction data. The structure analyses showed that DLaTiO₄ and DNdTiO₄ crystallized in the space group P4/nmm with a=3.7232(1) and c=12.3088(1) Å, and a=3.7039(1) and c=12.0883(1) Å, respectively. On the other hand, DYTiO₄ crystallized in the space group P2₁/c with a=11.460(1), b=5.2920(4), c=5.3628(5) Å and β=90.441(9)°. The loaded protons were found to statistically occupy the sites around an apical oxygen of TiO₆ octahedron in the interlayer of these compounds, rather than Na atom sites in NaLnTiO₄.     

Synthesis, Crystal and Magnetic Structures of the Sodium Ferrate (IV) Na4FeO4 Studied by Neutron Diffraction and Mössbauer Techniques

The alkali sodium ferrate (IV) Na₄FeO₄ has been prepared by solid-state reaction of sodium peroxide Na₂O₂ and wustite Fe_1−xO, in a molar ratio Na/Fe=4, at 400°C under vacuum. Powder X-ray and neutron diffraction studies indicate that Na₄FeO₄ crystallizes in the triclinic system P−1 with the cell parameters= a=8.4810(2) Å, b=5.7688(1) Å, c=6.5622(1) Å, α=124.662(2)°, β=98.848(2)°, γ=101.761(2)° and Z=2. Na₄FeO₄ is isotypic with the other known phases Na₄MO₄ (M=Ti, Cr, Mn, Co and Ge, Sn, Pb). The solid solution Na₄Fe_xCo_1−xO₄ exists for x=0-1 and we have followed the evolution of the cell parameters with x to determine the lattice parameters of the triclinic cell of Na₄FeO₄. A three-dimensional network of isolated FeO₄ tetrahedra connected by Na atoms characterizes the structure. This compound is antiferromagnetic below T_N=16 K. At 2 K the magnetic cell is twice the nuclear cell and the magnetic structure is collinear (μ_Fe=3.36(12) μ_B at 2 K). This black compound is highly hygroscopic. In water or on contact with the atmospheric moisture it is disproportionated in Fe³⁺ and Fe⁶⁺. The Mössbauer spectra of Na₄FeO₄ are fitted with one doublet (δ=− 0.22 mm/s, Δ=0.41 mm/s at 295 K) in the paramagnetic state and with a sextet at 8K. These parameters characterize Fe⁴⁺ high-spin in tetrahedral FeO₄ coordination.     

Syntheses and single-crystal structures of CsTh(MoO4)2Cl and Na4Th(WO4)4

Colorless crystals of CsTh(MoO₄)₂Cl and Na₄Th(WO₄)₄ have been synthesized at 993 K by the solid-state reactions of ThO₂, MoO₃, CsCl, and ThCl₄ with Na₂WO₄. Both compounds have been characterized by the single-crystal X-ray diffraction. The structure of CsTh(MoO₄)₂Cl is orthorhombic, consisting of two adjacent [Th(MoO₄)₂] layers separated by an ionic CsCl sublattice. It can be considered as an insertion compound of Th(MoO₄)₂ and reformulated as Th(MoO₄)₂·CsCl. The Th atom coordinates to seven monodentate MoO₄ tetrahedra and one Cl atom in a highly distorted square antiprism. Na₄Th(WO₄)₄ adopts a scheelite superlattice structure. The three-dimensional framework of Na₄Th(WO₄)₄ is constructed from corner-sharing ThO₈ square antiprisms and WO₄ tetrahedra. The space within the channels is filled by six-coordinate Na ions. Crystal data: CsTh(MoO₄)₂Cl, monoclinic, P2₁/c, Z=4, a=10.170(1) Å, b=10.030(1) Å, c=9.649(1) Å, β=95.671(2)°, V=979.5(2) Å³, R(F)=2.65% for I>2σ(I); Na₄Th(WO₄)₄, tetragonal, I4₁/a, Z=4, a=11.437(1) Å, c=11.833(2) Å, V=1547.7(4) Å³, R(F)=3.02% for I>2σ(I).     

Über metall-alkyl-verbindungen: XIV. Die kristallstrukturen von K[In(CH3)4], Rb[In(CH3)4] und Cs[In(CH3)4]

The crystal structure of KInMe₄ and CsInMe₄ have been determined from single crystal diffractometer data. Lattice parameters of RbInMe₄ obtained by powder methods are given. KInMe₄ and RbInMe₄ are isostructural (space group I4₁/amd), containing four formula units in the unit cell. CsInMe₄ belongs to space group P4? 2m with one formula unit per unit cell. Lattice parameters in Å: KInMe₄:a=9.904(2), c=8.132(2); RbInMe₄:a=10.208(2), c=8.146(2); CsInMe₄:a=7.459(1), c=4.163(1). All compounds consist of isolated alkali cations and tetrahedral InMe₄-anions. InC distances are 2.239(3) in KInMe₄ and 2.26(2) in CsInMe₄. The appearance of three different structure types of alkali metal tetramethyl indates is explained by the increasing alkali ion radii.     

Synthesis and crystal structure of three silver indium double phosphates

Three new silver indium double phosphates Ag₃In(PO₄)₂ (I), β-(II) and α-Ag₃In₂(PO₄)₃ (III) were synthesized by solid state method (I and II—700 °C, III—900 °C). Compounds I and II crystallize into a monoclinic system (I—sp. gr. C2/m, Z=2, a=8.7037(1)Å, b=5.4884(1)Å, c=7.3404(1)Å, β=93.897(1)°; II—sp. gr. C2/c, Z=4, a=12.6305(1)Å, b=12.8549(1)Å, c=6.5989(1)Å, β=113.842(1)°), and compound III crystallize into a hexagonal system (sp. gr. R-3c, Z=6, a=8.9943(1)Å, c=22.7134(1)Å). Their crystal structures were determined by the Rietveld analysis (I—R_p=6.47, R_wp=8.54; II—R_p=5.67, R_wp=6.40; III—R_p=7.30, R_wp=9.91). Structure of Ag₃In(PO₄)₂ is related to the sodium chromate structure type and is isotypic to α-Na₃In(PO₄)₂. The polymorphous modifications of β- and α-Ag₃In₂(PO₄)₃ are isostructural to sodium analogs (β- and α-Na₃In₂(PO₄)₃) and are related to alluaudite (II) and NASICON (III) structure types. Compounds I and II are not stable at temperature above 850 °C. Ag₃In(PO₄)₂ is decomposed providing silver orthophosphate Ag₃PO₄ and α-Ag₃In₂(PO₄)₂. β-Ag₃In₂(PO₄)₃ is transformed to α-Ag₃In₂(PO₄)_3.     

New 4234-type Intermetallic Borocarbides: Synthesis, Structure, and Magnetic Properties

New 4234-type compounds, structurally related to the n=4 member of the (LnC)_nNi₂B₂ homologous series of intermetallic borocarbides, were synthesized by arc-melting. Here we report that this structure type, previously observed only for Ni-based compounds, can be synthesized for a large number of transition elements. Further, we find it to be stable for medium through small lanthanides. The compounds have formulas Y₄T₂B₃C₄ [T=Fe, Co, Ni, Ru, Rh, and Ir], Ln₄T₂B₃C₄ [Ln=Er, Dy, and Gd; T=Fe and Co], Lu₄Ni₂B₃C₄, and Sc₄Ni₂B₃C₄. The unit cells are pseudo-tetragonal, with lattice parameters ranging from a=3.348(1) Å, c=25.90(1) Å for Sc₄Ni₂B₃C₄ to a=3.624(1) Å, c=26.63(1) Å for Y₄Rh₂B₃C₄. Structural investigation by exit-wave reconstruction is reported, showing the presence of twinning on the unit cell scale. The phases show either Curie- Weiss behavior with very small magnetic moments per transition metal atom or temperature-independent paramagnetism.     

Structural and transport properties of compounds in the CsHSO4-KH2PO4 system with a high potassium dihydrophosphate content

The (1?x)CsHSO₄-xKH₂PO₄ system was studied in a wide range of compositions (x = 0.05?0.97). Mixed salts with different crystal structures and different transport, thermodynamic, and thermal properties were shown to form. In these mixed (1?x)CsHSO₄-xKH₂PO₄ compounds (x = 0.05?0.5), solid solutions formed on the basis of the compound with a crystal structure Cs₃(HSO₄)₂(H₂PO₄) (C2/c). As the content of KH₂PO₄ increased further, another compound with a crystal structure, CsH₅(PO₄)₂ (P2₁/c), formed and existed up to x = 0.95. At x ≥ 0.7, KH₂PO₄ existed as an individual phase along with CsH₅(PO₄)₂; its content increased considerably at x ≥ 0.9. The low conductivities and high activation energies of (1?x)CsHSO₄-xKH₂PO₄ at x = 0.6?0.95 were close to those for CsH₅(PO₄)₂. The compounds with x = 0.5–0.9 showed low thermal stability corresponding to the individual CsH₅(PO₄)₂ phase.     

Structures and syntheses of framework triuranyl diarsenate hydrates

Two homeotypic hydrated uranyl arsenates, (UO₂)[(UO₂)(AsO₄)]₂(H₂O)₄, UAs4, and (UO₂)[(UO₂)(AsO₄)]₂(H₂O)₅, UAs5 were synthesized by hydrothermal methods. Intensity data were collected at room temperature using MoKα X-radiation and a CCD-based area detector. Their crystal structures were solved by direct methods and refined by full-matrix least-squares techniques on the basis of F² to agreement indices (UAs4, UAs5) wR₂=0.116, 0.060, for all data, and R₁=0.046, 0.033, calculated for 3176, 5306 unique observed reflections (|F_o|>4σ_F) respectively. UAs4 is monoclinic, space group P2₁/c, Z=4, a=11.238(1), b=7.152(1), c=21.941(2)Å, β=104.576(2)°, V=1706.8(1)ų, D_calc=4.51 g/cm³. UAs5 is orthorhombic, space group Pca2₁, Z=4, a=20.133(2), b=11.695(1), c=7.154(1)Å, V=1684.4(1)ų, D_calc=4.65 g/cm³. Both structures contain sheets of arsenate tetrahedra and uranyl pentagonal bipyramids, with composition [(UO₂)(AsO₄)]¹⁻ and the uranophane sheet anion-topology. The sheets are connected by a uranyl pentagonal bipyramid in the interlayer that shares corners with an arsenate tetrahedron on each of two adjacent sheets, resulting in open-frameworks with isolated H₂O groups in the larger cavities of the structures. The uranyl arsenate sheet in UAs4 is relatively planar, and is topologically identical with the uranyl phosphate sheet in (UO₂)[(UO₂)(PO₄)]₂(H₂O)₄. The uranyl arsenate sheet in UAs5 is the same geometrical isomer as in UAs4, but is highly corrugated, exhibiting approximately right angle bends of the sheet after every second uranyl arsenate chain repeat.     

Cation distribution in (M′, M)3Se4: II. (V,Ti)3Se4 and (Cr,V)3Se4

The cation distribution among the two crystallographic cation sites of the Cr₃S₄ structure was determined in VTi₂Se₄ and VCr₂Se₄ by high-resolution neutron diffraction, using Rietveld analysis. The results showed a considerable disorder but they nevertheless revealed the site preference of V atoms for the 2(a) site in both compounds. The compositional changes of the lattice parameters and the transition temperatures to the CdI₂-type structure in (V_xTi_1−x)₃Se₄ and (Cr_xV_1−x)₃Se₄ were compared with those in (Cr_xTi_1−x)₃Se₄ and (Fe_xCr_1−x)₃Se₄, and discussed from the viewpoint of the site preference of the cation.     

Synthesis, crystal structure, and vibrational spectra of MVO(SO4)2 (M = Rb, Cs, or Tl)

A series of MVO(SO₄)₂ vanadium complexes, where M = Rb, Cs, or Tl, were prepared, and their crystal structures and physicochemical properties studied. The rubidium and thallium compounds of this series were found to be isostructural to each other and to crystallize, like KVO(SO₄)₂ and NH₄VO(SO₄)₂, in orthorhombic system (space group P2₁2₁2₁, No. 19, Z = 4) with the unit cell parameters a = 4.9735(2) Å, b=8.7894(4) Å, c = 16.6968(8) Å, V = 729.88 ų (Rb); and a = 4.9636(1) Å, b = 8.7399(2) Å, c = 16.8598(4) Å, V = 731.39 ų (Tl). The cesium compound was found to crystallize in monoclinic system (space group P2₁/a, No. 14-2, Z = 4): a = 10.0968(6) Å, b = 8.9131(4) Å, c = 9.8675(5) Å, β = 114.640(2)°, V = 807.16 ų. The MVO(SO₄)₂ crystal structure is built of VO₆ octahedra, which are linked into layers by bridging SO₄ groups. At the apex of each VO₆ octahedron, there is a short V-O terminal bond having a length of 1.54(1) Å (Rb), 1.57(2) Å (Tl), and 1.52(4) Å (Cs).     

Synthesis and study of cesium-containing phosphates with a β-tridymite structure

Complex phosphates CsMg_{1 ? x} M _x PO₄ (M = Mn, Co, Cu, Zn), containing cesium and metals in the oxidation state +2, have been synthesized, and their structure and thermal behavior have been studied. Continuous solid solutions (0 ?? x ?? 1) of the ??-tridymite structure type are formed in the CsMg_{1 ? x} Mn _x PO₄, CsMg_{1 ? x} Co _x PO₄, and CsMg_{1 ? x} Zn _x PO₄ systems, whereas limited solid solutions (0 ?? x ?? 0.4) are formed in the CsMg_{1 ? x} Cu _x PO₄ system. Based on DTA data, phase transitions have been revealed in the cobalt-, copper-, and zinc-containing phosphates, and the orthorhombic or monoclinic crystal system has been identified. Unit cell parameters of the solid solutions have been calculated. Thermal expansion of the CsMPO₄ phosphates has been studied.     

The electronic structures of tetrahedral oxo-complexes. The nature of the “charge transfer” transitions

The electronic structures of MnO^?₄, MnO^2?₄, MnO^3?₄, CrO^2?₄, CrO^3?₄, VO^3?₄, RuO₄, RuO^?₄, RuO^2?₄, TcO^?₄ and MoO^2?₄ have been investigated using the Hartree-Fock-Slater Discrete Variational Method. The calculated ordering of the valence orbitals of all the comlexes is: t₁, 4t₂, 3a₁, 1c, 3t₂, with t₁ the orbital of highest energy. The calculated single transition energies are in good agreement with experimental values and indicate the uniform assignment: t₁ → 2e(v₁), 4t₂ → 2e(v₂). t₁ → 5t₂(v₃), and 4t₂ → 5t₂(v₄). A/D values, calculated from the theory of magnetic circular dichroism (MDC) also support this assignment.Population analyses reveal that all complexes, whether d⁰, d¹ or d², have d-orbital populations close to those of the corresponding M²⁺ ions in which two electrons have been removed from the (n + 1)s orbital of M. This is also true of the excited states, such as t₁ → 2e and 4t₂ → 2e, where a transfer of charge from the ligands to the metal has previously been assumed. It is shown that, instead of a transfer of charge from ligands to metal, electronic excitation consists of a rearrangement of electron density both at the ligands and at the metal.