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The substitution of lithium for copper in Cu2ZnSnS4(CZTS) has been experimentally and theoretically investigated. Formally, the (Cu1–xLix)ZnSnS4system exhibits two well-defined solid solutions. Indeed, single crystal structural analyses demonstrate that the low (x< 0.4) and high (x> 0.6) lithium-content compounds adopt the kesterite structure and the wurtz-kesterite structure, respectively. For xbetween 0.4 and 0.6, the two aforementioned structure types coexist. Moreover, 119Sn NMR analyses carried out on a (Cu0.7Li0.3)2ZnSnS4sample clearly indicate that lithium replaces copper preferentially on two of the three available 2-fold crystallographic sites commonly occupied by Cu and Zn in disordered kesterite. Furthermore, the observed individual lines in the NMR spectrum suggest that the propensity of Cu and Zn atoms to be randomly distributed over the 2c and 2d crystallographic sites is lowered when lithium is partially substituted for copper. Additionally, the first-principles calculations provide insights into the arrangement of Li atoms as a function of the Cu/Zn disorder and its effect on the structural (lattice parameters) and optical properties of CZTS (band gap evolution). Those calculations agree with the experimental observations and account for the evolutions of the unit cell parameters as well as for the increase of band gap when the Li-content increases. The calculation of the formation enthalpy of point defect unambiguously indicates that Li modifies the Cu/Zn disorder in a manner similar to the change of Cu/Zn disorder induced by Ag alloying. Overall, it was found that Li alloying is a versatile way of tuning the optoelectronic properties of CZTS making it a good candidate as wide band gap materials for the top cells of tandem solar cells.

We report here two original low temperature routes for the synthesis of nanostructured particles of ptype TCOs CuGaO2and LaOCuS. Light grey CuGaO2nanolayered particles ∼300 nm large and 5 nm thick were prepared from a hydrothermal synthetic route using soluble hydrated metal nitrates as precursors and ethylene glycol EG as reducing agent. We found then that the initial pH of the precursors solution is a key parameter to tune the particle sizes from 2 µm to 300 nm and subsequently the colour from dark brown to light grey of the CuGaO2powder. LaOCuS was obtained for the first time as greyish nanolayered particles ∼100 nm large and 10 nm thick via a solvothermal route in ethylene diamine with hydrate chloride lanthanum, copper mono oxide and elemental sulphur as precursors. We found that the control of the chloride lanthanum precursor hydration rate is of prime importance to achieve pure material and to tune the colour of the LaOCuS sample. Both CuGaO2and LaOCuS nanolayered particles synthesized via these soft chemistry routes exhibit all the characteristics of transparent ptype semiconductors

The phosphorescence mechanisms of various phosphors were explored by taking into consideration the presence of interactions between dopant cations and vacancies as well as the effect of co-dopant cations on these interactions. Our study indicates that the distribution of dopant and co-dopant cations around vacancies is not random, and luminescent properties are strongly influenced by this nonrandom distribution. To a first approximation, the ionization potentials of dopants, co-dopants, and host cations can be used to rationalize their tendencies for this nonrandom distribution. On the basis of our analysis, we explained the properties of known phosphorescent materials, examined several factors important for designing new improved phosphors, and discussed how point defects might affect phosphorescence as well as fluorescence.

The existing mechanisms proposed to explain the phosphorescence of SrAl2O4:Eu²⁺,Dy³⁺ and related phosphors were found to be inconsistent with a number of important experimental and theoretical observations. We formulated a new mechanism of phosphorescence on the basis of the facts that the d orbitals of Eu²⁺ are located near the conduction band bottom of SrAl2O4, that the Eu²⁺ concentration decreases during UV excitation, and that trace amounts of Eu³⁺ are always present in these phosphors. In our mechanism, some Eu²⁺ ions are oxidized to Eu³⁺ under UV, and the released electrons are trapped at the oxygen vacancy levels located in the vicinity of the photogenerated Eu³⁺ cations. The phosphorescence arises from the recombination of these trapped electrons around the photogenerated Eu³⁺ sites with emission at 520 nm. The codopant Dy³⁺ enhances the phosphorescence by increasing the number and the depth of electron traps, and the codopant B³⁺ enhances the phosphorescence by increasing the depth of electron traps. We also probed the origin of another emission at 450 nm of SrAl2O4:Eu²⁺ that occurs at low temperatures. Our analysis indicates that this emission is caused by a charge transfer from oxygen to Eu³⁺ cations and is associated with a hole trapping.

In an effort to find new UV absorbers, the optical properties of CeO2, SrCeO3, and Sr2CeO4 were examined by UV−visible diffuse reflectance measurements and electron energy-loss spectroscopy (EELS), and their electronic structures were investigated on the basis of first-principles density functional theory (DFT) calculations. The extinction coefficient k and the refractive index n determined from the loss function Im(−1/ε) by EELS were compared with the corresponding quantities calculated from DFT calculations. The UV absorption thresholds of these materials were determined by the electron excitation from the O 2p anionic band to the empty Ce 4f orbitals. The calculated and measured refractive indices were in satisfactory agreement. The applicability of CeO2, SrCeO3, and Sr2CeO4 as potential UV absorbers was assessed.

The new 1D chalcogenophosphate material NaV0.837(6)P2S6 has been synthesized and its structure determined by X-ray powder diffraction analysis. This compound crystallizes in the monoclinic space group P21/n with a = 6.9677(3) Å, b = 5.9059(2) Å, c = 21.4537(8) Å, and β = 92.962(2)° [Z = 4, V = 881.66(8) ų]. The Rietveld refinement led to Rp/Rwp = 0.0208/0.0271 (for 94 parameters refined). The material is isostructural with 1D-NaCrP2S6 and contains infinite (¹/∞)[V0.837(6)P2S6]^- chains consisting of randomly occupied edge-sharing [VS6] octahedra defining zigzag (¹/∞)[VS4] ribbons that are capped by tetradendate [P2S6] ethane-like groups linked to three successive [VS6] polyhedra. Because of the nonstoichiometry of the phase, the charge balance can be written as Na⁺(V⁴⁺)0.486(V³⁺)0.351(P⁴⁺)2(S^2-)6. NaV0.837(6)P2S6 is soluble in strongly polar organic solvents such as N-methylformamide (NMF). The exfoliation of NaV0.837(6)P2S6 in NMF leads to gels or to colored colloidal solutions with complex fluid behavior that depends strongly on concentration.

The Ce−S−Si system has been explored in search of new, yellow nontoxic pigments. We prepared a new Ce−S−Si phase (Ce6Si4S17), determined the crystal structures of Ce2SiS5, Ce4Si3S12, and Ce6Si4S17, and measured the chromatic properties of these Ce−S−Si phases. The differences in the yellow hue of these compounds were probed by analyzing their Ce³⁺ ion environments and calculating their electronic band structures. Ce6Si4S17 is distinguished from Ce2SiS5 and Ce4Si3S12 in terms of the Ce³⁺ structural environment and the Ce³⁺ 4f¹→5d⁰ transition gap. This gap is wider for Ce6Si4S17 than for Ce2SiS5 and Ce4Si3S12 (i.e., 2.51 vs. ~2.36 eV), and Ce6Si4S17 exhibits room-temperature luminescence whereas Ce2SiS5 and Ce4Si3S12 do not. Ce4Si3S12 and Ce6Si4S17 possess chromatic properties similar to those found for industrial pigments such as PbCrO4, BiVO4, and CdS, and show thermal and chemical stabilities.

Detailed results of DFT band structure calculations for the α-M₃N₂ (M = Be, Mg, Ca) binary nitrides are reported. The cell parameters and atomic positions were optimized with the molecular dynamics pseudopotential approach of the Vienna ab initio simulation program (VASP). The optimized structures were subsequently calculated with the WIEN97 program, based on the full potential linearised augmented plane waves (FP-LAPW) method, within the framework of density functional theory (DFT). As expected, the valence band is composed of the nitrogen 2p states, while the conduction band comprises the metallic states. The band gap was found to decrease when going from Be to Mg and Ca. This counterintuitive result is due to the existence of a significant anion–cation covalent interaction which decreases when going from Be to Mg and Ca. The electronic structures of the mixed nitride CaMg₂N₂ and of the hypothetical α-M₃N₂ (M = Sr, Ba) phases are also discussed in the light of the above results.

Two new alkali metal chromium thiophosphates, Na3Cr2P3S12and K3Cr2P3S12, have been synthesized and their structure determined from single-crystal or powder X-ray diffraction analyses. These isostructural compounds, which exhibit a novel structural arrangement, crystallize in the monoclinic system (space group P21/c) with the cell parameters a=17.4076(10) Å, b=11.1723(10) Å, c=19.2502(11) Å, β=149.731(3)° (V=1887.1(2) Å3, Z=4) and a=17.9690(14) Å, b=12.0607(5) Å, c=19.3109(16) Å, β=150.008(3)° (V=2091.98(16) Å3, Z=4) for Na3Cr2P3S12(I) and K3Cr2P3S12(II), respectively. For (I), the single-crystal refinement led to R/Rw(F2)=0.0417/0.0650 (for 4125 independent reflections and 182 refined parameters). For (II), the Rietveld refinement led to Rp/Rwp=0.0181/0.0233 (for 90 refined parameters). In both materials, the structures consist of 1∞[Cr2P3S12]3−chains built upon two edge-sharing [CrS6] octahedra capped by two [PS4] tetrahedra defining isolated [Cr2P2S12]−8entities. These entities are linked to each other through an extra [PS4] tetrahedral group. Magnetic measurements evidence antiferromagnetic coupling between Cr3+cations. The charge balance of the phase is MI3CrIII2PV3S−II12.

The structural and electronic consequences of the metal–metal sigma bonding in the hexagonal perovskite sulfides were examined by calculating the electronic band structures of Sr9/8TiS3and Sr8/7TiS3, by synthesizing Sr8/7[Ti6/7Fe1/7]S3and characterizing its crystal structure, and by measuring the magnetic susceptibilities of Sr9/8TiS3, Sr8/7TiS3, and Sr8/7[Ti6/7Fe1/7]S3. The (TiS3)∞chains of Sr9/8TiS3and Sr8/7TiS3contain oligomer units (Oh)n(n=4, 5) made up of face-sharing TiS6octahedra (Oh). Given the (TiS3)∞chains aligned along the zdirection, the only occupied d-block levels of each (TiS3)∞chain are the most sigma bonding level of each (Oh)noligomer, which is constructed from its nz2orbitals. This “n-orbital two-electron” metal–metal sigma bonding controls the d-orbital density distribution and the Ti–Ti distances of the (Oh)noligomers and is ultimately responsible for the semiconducting property of Sr9/8TiS3, Sr8/7TiS3, and Sr8/7[Ti6/7Fe1/7]S3. The Sr8/7[Ti6/7Fe1/7]S3structure is described by the trigonal symmetry, R̄3m(00γ)0ssuperspace group with the following parameters: as=11.4935(11) Å, cs=2.9986(7) Å, q=0.57161(15) c*, and Vs=343.05(15) Å3.

We examined the feasibility of preparing new high-pressure polymorphs of IrTe2by determining the relative energies and unit cell volumes of known and hypothetical forms of IrTe2on the basis of first-principles electronic band structure calculations using the Vienna ab initiosimulation package (VASP). The IrTe2polymorphs included in our analysis are three known phases, i.e., the polymeric CdI2-type, pyrite-type, and monoclinic IrTe2phases, as well as four hypothetical phases, i.e., ramsdelite-type, pyrolusite-type, IrS2-type, and marcasite-type phases. The charge balances of these IrTe2phases were analyzed by carrying out extended Hückel tight-binding electronic band structure calculations for the crystal structures optimized by VASP calculations.

The hexagonal perovskite-type oxides AxBO3(A=Ca, Sr, Ba; B=Co, Ni) consist of (BO3)∞chains made up of face-sharing BO6octahedra and BO6trigonal prisms. On the basis of molecular orbital calculations for their structural building blocks we examined why the transition metal atoms in the trigonal prisms of Sr9/7NiO3and Sr14/11CoO3occupy the positions away from their trigonal prism centers and why Ba6/5NiO3and Ca3/2CoO3exhibit apparently puzzling magnetic properties. Our analysis indicates that the structural building units of the (BO3)∞chains in these oxides adopt high-spin states to reduce the metal–metal σ-antibonding interactions between adjacent metal atoms as well as the on-site repulsion. This finding led us to predict the number of unpaired spins that the oxides Sr9/7NiO3, Sr6/5CoO3, and Sr14/11CoO3are expected to have.

CeSbS2Br2(I), Ce1/2La1/2SbS2Br2(II), and LaSbS2Br2(III) have been synthesized at 700°C from a mixture of LnBr3, Ln2S3, Sb, and S and characterized by single-crystal X-ray diffraction. The three phases are isostructural (space group P21/c, Z=4) and crystallize in a novel, dense, bidimensional structure with cell parameters a=8.709(3) Å, b=9.187(2) Å, c=17.397(5) Å β=104.26(3)° for I, a=8.739(7) Å, b=9.219(7) Å, c=17.41(2) Å, β=104.3(1)° for II, and a=8.785(1) Å, b=9.236(2) Å, c=17.372(3) Å, β=104.09(2)° for III. In these compounds, [LnS5Br4] and [LnS3Br6] (Ln=Ce, La) distorted tricapped trigonal prisms define infinite 2∞[LnS2Br2] layers counterbalanced and capped by antimony cations. In good accordance with the structural features, the charge balance in these materials is to be written LnIIISbIIIS−II2Br−I2. These compounds exhibit a yellow hue with a measured absorption threshold of 2.42(1), 2.55(1), and 2.72(1) eV for I, II, and III, respectively. In the two cerium containing bromothioantimonates I and II, the origin of the color is assigned to a Ce–4f→Ce–5delectronic transition, which shifts to higher energy from I to II due either to a matrix effect (increase of the mean Ln–S distances under the substitution of Ce for La) or to an atomic ordering between Ce and La cations on the Ln(1) and Ln(2) crystallographic sites. In contrast, the electronic transition at play in III involves a charge transfer from the bromine and sulfur ions to the antimony ions, the latter contributing substantially to the lowermost levels of the conduction band.

For magnetic solids with several unpaired spins per spin site, the average spin orbital interaction energies 〈Δe〉 and the average spin orbital interaction energy squares 〈(Δe)2〉 were defined as a qualitative measure for the strengths of their antiferromagnetic spin exchange interactions. The trends in the antiferromagnetic spin exchange interactions of the magnetic solids containing MnF5chains and CrX2(X=O, S) layers were examined in terms of the 〈Δe〉 and 〈(Δe)2〉 values calculated for their spin dimers.

Ce-containing chalcogenides may exhibit interesting chromatic properties due to the presence of a CeIII-5f/CeIII-4d gap. In such insulating materials, color varies from red to yellow depending on the covalent character of the Ce–S bond. Thanks to this correlation, a continuous modification of the Ce–S bond characteristics may be induced to control the hue. Attempts in modifying these bonds have been undertaken by synthesizing the solid solution Y1−xCexPS4(x=0, 0.005, 0.01, 0.05 and 0.1), YPS4being colorless. The substitution of Y3+cations (rY3+(CN8)=1.019 Å) for Ce3+cations (rCe3+(CN8)=1.143 Å) let expect a regular shift of the physical parameters deemed to influence the chromatic properties. Nevertheless, diffuse reflectance measurements did not evidence any absorption threshold shift vs. xin the Y1−xCexPS4series. The lack of sizeable influence of the Y/Ce substitution on the color is correlated not only to the intrasite, band to band nature of the Ce-5f→Ce-4d transition, but also to the occurrence of local relaxations around Ce in the YPS4:Ce solid solution insuring a chemical environment of the rare earth very similar to that observed in CePS4. EXAFS measurements performed at the Y–K and the Ce–LIIIedges evidence the maintaining of the average Y–S and Ce–S distances in the Y1−xCexPS4solution from x=0 to x=1 as they are in the non-substituted end compounds YPS4and CePS4.

The electronic band structures of A2Mo9S11(A=K, Rb) and K1.8Mo9S11are examined by extended Hückel tight binding calculations. K2Mo9S11and K1.8Mo9S11are metallic and exhibit resistivity anomalies below ∼115 and ∼80 K, respectively. The origin of these anomalies is explained in terms of their Fermi surfaces. Our study indicates that the resistivity anomalies of these compounds are caused by the partial nesting of their two-dimensional Fermi surfaces and that both K2Mo9S11and Rb2Mo9S11should exhibit a charge density wave phenomenon.

The distribution of the Pb and Sb atoms in the (Pb, Sb)S layers of the misfit compound [(Pb, Sb)S]2.28NbS2was investigated by scanning tunneling microscopy (STM) and atomic force microscopy (AFM). This compound has NaCl-type MS(M=Pb, Sb) layers (Q-layers) alternating with NbS2layers (H-layers) in which the Nb atoms are located in slightly distorted trigonal prism sites. Both the H- and Q-layers of [(Pb, Sb)S]2.28NbS2were imaged by STM and AFM. The atomic-scale STM and AFM images were analyzed in terms of the partial and total electron density plots calculated for the Q- and H-layers. The STM images of the Q-layers allowed us to detect all the constitutive atoms of the Q-layers with a short-range ordering of pure Pb and Sb rows in the aQmodulation direction.

The flexibility of the MPS−4chains of KMPS4(M=Ni, Pd) was examined by performing contact mode atomic force microscopy (AFM) measurements for the (001) surface of KNiPS4and also by performing extended Hückel tight binding calculations for the [M(PS4)2]4−entities of KMPS4. The observed AFM images were analyzed by calculating the total electron density plots for an isolated [NiPS4]−slab of the (001) surface. Our calculations show that the PS3−4ions are more strongly bound to the Pd2+ions in KPdPS4than to the Ni2+ions in KNiPS4, and that the bonding between the PS3−4anions and M2+(M=Ni, Pd) cations is flexible with respect to the rotational motions of the PS3−4anions. The AFM images recorded for the (001) surface of KNiPS4indicate that the PS3−4anions on the surface undergo a rotational relaxation when the scanning tip passes by.

The UV–Visible (350–900 nm), infrared and Raman (30–800 cm⁻¹) spectra of a new transition metal thiophosphate solid compound, KPdPS4, were analyzed using powder samples and single-crystal platelets. From polarized absorbance measurements, the main electronic transitions of the ¹F2 ← ¹A1 type due to the (PS4)³⁻ groups are localized in the 400–520 nm range and all the expected infrared vibrational modes were observed in the 600–30 cm⁻¹ region; various polarized Raman measurements were also performed. The vibrational assignments were then checked by complete valence force field lattice dynamics calculations in the different symmetry blocks of the tetragonal crystal structure (D4h¹⁴). Potential energy distributions and mean squared vibrational amplitude calculations revealed strong ν(Pd–S) and δ(S–P–S) couplings in the one-dimensional inorganic polymer anionic ¹∞[PdPS]4]⁻ chains and remarkably high ν)Pd–S) stretching modes near 350 cm⁻¹. Compared with results for the analogous Ni(II) compound, there was a significant increase in the M– S force constants, varying from 75 N m⁻¹ (Ni– S) to 90 N m⁻¹ (Pd– S) in accordance with the Pauling electronegativity scale. Furthermore, various resonance Raman spectra of micrometer-sized samples were recorded using a confocal microscope instrument in order to characterize not only the existence of chains having a distribution of length but also some Raman impurity bands coming from the dithiophosphate compound, K4Pd(PS4)2. Also, resonance Raman spectra of powder samples were recorded using several exciting radiation wavelengths over the range 800–500 nm in order to probe the nature of the low-energy electronic transition at 658 nm; the Raman excitation profiles of several fundamentals were thus established and they demonstrate that both totally symmetric and non-totally symmetric stretching and bending modes of the PS4 and PdS4 groups are markedly enhanced. We therefore conclude that several ligand to metal charge-transfer electronic transitions are overlapped and involved in vibronic coupling mechanisms with higher energy bands. Finally, a comparison of the induced Raman scattering processes in the Cu3PS4, KNiPS4 and KPdPS4 solid compounds showed that the ligand to metal charge transfers and the crystal field effects have a strong influence on the optical and vibronic properties of these thiophosphate compounds. Copyright © 1999 John Wiley & Sons, Ltd.

The UV–visible (350–900 nm), infrared and Raman (30–800 cm⁻¹) spectra of a new transition metal thiophosphate solid compound, (PPh4)3 [(NiPS4)3], were analyzed using powder samples. Electronic transitions of the ¹F2← ¹ A1 type originating in the (PS4)³⁻ groups were detected from visible absorbance measurements in the 440–520 nm range and most of the expected infrared and Raman vibrational modes of the trimetallic ring anion [Ni3P3S12]³⁻ were observed in the 600–30 cm⁻¹ region. Also, resonance Raman spectra were recorded using exciting radiation of several wavelengths in the 680–450 nm range and the Raman excitation profiles of several fundamentals were established: they all peak near 488 nm and exhibit the strongest enhancements for totally symmetric and non-totally symmetric stretching and bending modes of (NiS4) groups. It is therefore concluded that several ligand to metal charge-transfer electronic transitions are overlapped and involved in vibronic coupling mechanisms. Furthermore, the vibrational assignments were checked by a valence force field calculation for an isolated [Ni3P3S12]³⁻ anion of C3v symmetry. The potential energy distributions and mean squared vibrational amplitudes revealed strong ν(Ni–S) and δ(S–P–S) couplings and relatively high ν(Ni–S) stretching modes at near 310 cm⁻¹. Compared with results in the one-dimensional KNiPS4 compound containing infinite anionic chains ∞ ¹[NiPS4]⁻, one notes a force constant increase on the P—S exocyclic (µ1) bonds, no change on the bridged (µ2 and µ3) P—S bonds and a slight increase in the Ni–S stretching force constants varying from 75 to 85 N m⁻¹ in accordance with a localized ligand to metal charge-transfer mechanism. Hence a comparison of the induced Raman scattering processes in the (PPh4)3 [(NiPS4)3] and KNiPS4 solid compounds shows that the ligand to metal charge transfers and the crystal field effects have a strong influence on the vibrational properties in these thiophosphate compounds. Copyright © 1999 John Wiley & Sons, Ltd.

Since the discovery of a monoclinic phase Cr₂Sn₃Se₇, it has been found that, for the same composition, an orthorhombic phase exists. It is described in the Pnma space group with a = 23.097(1) Å, b = 3.8307(2) Å, and c = 12.5414(6) Å. The structure, refined to a reliability factor R_F = 2.4%, is built upon [M₆Se₁₄]¹_∞ blocks (M = Cr(III) and Sn(IV)) defining 2,4 tunnels occupied by Sn(II) atoms in bicapped trigonal prisms. The orthorhombic Cr₂Sn₃Se₇ structure differs from the monoclinic one through the occurrence of [M₆Se₁₄]¹_∞ blocks instead of [_MSe₂]²_∞ layers. The magnetic susceptibility variation versus the applied magnetic field suggests a spin glass or a superparamagnetism behavior at low temperature. Copyright 1995, 1999 Academic Press

The reaction of Cu with a molten mixture of A2S/P2S5 (A = K, Rb, Cs) produced the quaternary compounds A2CuP3S9 (A = K, Rb) and Cs2Cu2P2S6. The reaction of Cu with a molten mixture of K2S/P2S5/S produced the quaternary compound K3CuP2S7. A2CuP3S9 (A = K, Rb); I, II, respectively) crystallizes in the space group P21/n (no. 14) for I:  a = 6.8331(6) Å, b = 23.562(2) Å, c = 9.5415(7) Å, β = 100.242(7)°, Z = 4, V = 1511.8(4) ų, ρcalc = 2.298 g/cm³. Cs2Cu2P2S6 (III) crystallizes in the space group P21/c (no. 14) with a = 9.538(3) Å, b = 12.793(4) Å, c = 10.429(4) Å, β = 103.76(2)°, Z = 4, V = 1236.1(7) ų, ρcalc = 3.478 g/cm³. K3CuP2S7 (IV) crystallizes in the space group P21/a (no. 14) with a = 13.113(5) Å, b = 6.702(3) Å, c = 15.141(7) Å, β = 115.13(1)°, Z = 4, V = 1315(1) ų, ρcalc = 2.35 g/cm³. The structure of I−II consists of novel one-dimensional [CuP3S9]n^2n- chains separated by A⁺ cations. The chains run along the crystallographic b-axis. The Cu⁺ cation is in tetrahedral coordination with the cyclic [P3S9]^3- anion, a new polythiophosphate unit. The structure of III has one-dimensional [Cu2P2S6]n^2n- chains separated by Cs⁺ cations. The chains consists of alternating [Cu2]²⁺ dimers linked by the ethane-like [P2S6]^4- units. The structure of IV is also one-dimensional, with [CuP2S7]n^3n- chains separated by K⁺ ions. The Cu⁺ ions are in a slightly distorted trigonal planar environment with the [P2S7]^4- units. Differential thermal analysis, far-IR, Raman spectroscopy, and optical spectroscopic data are reported. The results of a band structure calculation at the DFT-LMTO level for K2CuP3S9 are also discussed.

The structure of CePS4 has been determined from single-crystal X-ray diffraction data (I41/acd space group, a = b = 10.9228(3) Å, c = 19.3998(6) Å, V = 2314.5(2) ų, Z = 16). The refinement, conducted from 547 independent reflections (I > 3σ(I) and 30 variables) led to RF (%) = 1.83 and RwF (%) = 2.36. Diffuse reflectance spectra of CePS4 and of the La1-xCexPS4 series indicated that the electronic absorption mechanism in CePS4, a 4f¹ → 5d⁰ transition on the Ce^III ions, is the same as in γ-Ce2S3, with only the band gap width being modified. To this transition corresponds an absorption threshold responsible for the yellow hue of the thiophosphate at about 2.5 eV. Band structure calculation (TB-LMTO-ASA) confirms the experimental evidence of the Ce^III 4f¹ → 5d⁰ transition. Comparisons between CePS4 and γ-Ce2S3 through their electronic localized functions revealed the inductive effect of the P−S covalent bonding on the Ce−S bond, with the resulting increase of the Ce^III 4f¹ → 5d⁰ transition in the thiophosphate as compared to the sulfide. This increase is ascribed, in part, to a lowering of the 4f block because of the decreased screening effect of the more ionic Ce−S bonding in CePS4.

In transition metal compounds of edge-sharing square planarMX4units (M=group 10, group 11;X=O, S, Se), a square planar to rectangular distortion is observed. The causes for this distortion inMX2ladder chains,M3X4honeycomb layers, and 3DMXlattices were examined by performing extended Hückel tight binding electronic band structure calculations. The primary cause for the distortion is the reduction of the four-electron two-orbital destabilizing interactions among thep-orbitals ofX.

BaCoS2−δconsists of at least three different polymorphs: two that are stoichiometric and one that is potentially sulfur deficient with 0.0 ≤ δ ≤ 0.2. Two of these polymorphs were investigated here: a tetragonal single crystalP4/nmm,a= 4.568(1) Å,c= 8.942(2) Å (δ ≈ 0), and polycrystalline powderCmma,a= 6.4390(3) Å,b= 6.4909(3) Å,c= 8.9379(4) Å (δ ≈ 0.2). Room temperature TEM studies show that several classes of superstructures exist in the stoichiometric single crystals of this phase; on cooling the TEM diffraction patterns change and become more complex. Temperature-dependent lattice constants of polycrystalline BaCoS2−δshow anomalies near −60°C. BaCoS2−δis a metastable compound that is prepared above 850°C and subsequently quenched. Synthetic studies show that (1) at the preparation temperature BaCoS2is in equilibrium with S vapor at pressures on the order of an atmosphere, producing a nonstoichiometric phase BaCoS2−δ; (2) adding some excess sulfur can reduce δ to zero; and (3) too much excess sulfur results in partial or complete melting of the system (however, stoichiometric BaCoS2crystals can be obtained from those melts). Magnetic susceptibility measurements verify that the Co moments order antiferromagnetically at 310 K. At higher temperatures a Curie–Weiss fit to the data gives μeff= 2.14(4) μB/Co and θ = 150(20) K; these data are consistent with a low spin state for Co2+(d7).

Nickel ditelluride was prepared in different ways. Single crystal X-ray investigations reveal that the products are always nonstoichometric with respect to the Ni content. Relatively short intra- and interslab Te–Te contacts are indicative of a polymeric network with multiple Te–Te bonds explaining the very lowc/avalue of 1.37 of the hexagonal cell. Experimental valence band spectra (UPS) confirm that NiTe2is a metal. The emission at the Fermi levelEFis due to Nidand Tepstates. This assignment is supported by the results of the calculated density of states curve (DOS) which demonstrates that Tepstates contribute more than 50% to the DOS atEF. Core level spectra (XPS) give evidence that Ni is in the paramagnetic Ni(II) (d8) state. The chemical shift of the Te 3dcore level leads to the assignment of an oxidation state of −1, in good agreement with the oxidation state of about −1.2 deduced from the relation between the Te–Te distances versus oxidation states of the anion in (Te2)2−, Te2−. The three-dimensional character of NiTe2deduced from the crystal structure is further confirmed by the calculated energy dispersionE(k).

The crystal structures of Cu2ZnSnS4and the nonstoichiometric Cu‐poor phase Cu1.71Zn1.18Sn0.99S4are determined by single crystal and powder XRD.

[(NH2)2C=NH2] 2Ti5O5F12is synthesized by microwave‐assisted solvothermal reaction of TiF4and [(NH2)2C=NH]·HCl (EtOH, microwaves, autoclave, 190 °C, 1 h).

Pure β‐Co1‐xMgxMoO4(0 ≤ x ≤ 1) solid solutions are prepared by solid state reactions of stoichiometric mixtures of MoO3, Co3O4, and MgO (alumina crucible, 700 °C, 20 h).

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For Abstract see ChemInform Abstract in Full Text.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.

ChemInform is a weekly Abstracting Service, delivering concise information at a glance that was extracted from about 100 leading journals. To access a ChemInform Abstract of an article which was published elsewhere, please select a “Full Text” option. The original article is trackable via the “References” option.