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1.
The apparent molar heat capacity, C p,, of aqueous NaOH has been measured at temperatures between 50 and 250°C and molalities from 0.05 to 1.5 mol-kg–1. Enthalpies of dilution L were also determined at 99°C and apparent molar relative enthalpies L were calculated up to 1.9 m. Measurements were performed by means of a flow calorimetric apparatus constructed in our laboratory and standardized for C p, and L with aqueous Na2SO4 and with the formation of water from its ions, respectively. Characteristics and performance of this calorimeter are described in detail. Pitzer's semiempirical equations are used for the representation of the results and a general fitting of C p, data is reported using also recent literature values measured between 4 and 55°C. The fitted parameters are finally utilized, through an integration procedure, to derive a general equation to calculate L at any temperature between 4 and 250°C.  相似文献   

2.
Summary Isocratic and gradient elution high performance liquid chromatographic measurements of the retention behavior of polystyrene homopolymers with molecular weights ranging from 2 kD to 390 kD were performed using mixed methylene chloride-methanol mobile phases of varying composition and a C-18 chemically bonded stationary phase supported on either 100 Å or 300 Å mean pore diameter silica. Isocratic measurements of the capacity factor, k, for different molecular weight homopolymers as a function of the volume fraction of methylene chloride, , permit determination of the critical composition, c, which renders k=1 and the local slope, S=–lnk/c of the lnk- isotherm at =c, and also the dependence of c and S on the degree of polymerization, M. Linear gradient elution measurements of c and S were also performed and compared to the corresponding isocratic measurements. The general retention behavior and the dependence of c and S on M compare favorably to the predictions of the theory of homopolymer retention and fractionation developed by Boehm, Martire, Armstrong, and Bui (BMAB). Comparison is also made between the present work and the experimental observations of other workers on related chromatographic systems involving hompolymer retention.  相似文献   

3.
Densities, heat capacities and conductivities of water-surfactant--cyclodextrin (-CD) ternary systems were determined at 25°C. The surfactants studied were sodium dodecylsulfate (NaDS) and dodecyltrimethylammonium bromide (DTAB). From conductivity data, apparent critical micelle concentrations (cmc*) and degree of ionization of micelles were obtained at a fixed -CD concentration (mCD). From the cmc* value and that in water (cmc) the stoichiometry of the surfactant--CD complex was calculated. At a given mCD, the apparent molar volume V,CD and heat capacity C,CD of -CD in the two surfactants were calculated as functions of surfactant concentration mS. For both NaDS and DTAB, V,CD increases with mS up to about the cmc beyond which it decreases to a constant value at high mS, the opposite is observed for C,CD. With NaDS, a jump in the C,CD vs, mS trend was detected and ascribed to a structural NaDS micellar transition. The apparent molar volume VS and heat capacity CS of NaDS and DTAB in the water--CD mixture 0.017 m were also obtained. From these properties and those in pure water, the volume VS and heat capacity CS of transfer of the surfactant from water to water+-CD mixture as functions of mS were calculated. For both surfactants, the VS vs. mS trends increase to the cmc and then decrease in a monotonic manner, whereas CS increases regularly with mS in the pre-micellar region and is essentially constant in the post-micellar region. The VS vs. mS trends were qualitatively explained in terms of dispersed, complexed and micellized surfactant contributions.  相似文献   

4.
A quantitative method of determining the quantum yield of irreversible photodegradation (C) of photochromic spiropyrans (SPP) was proposed for the first time. The C of a large number of SPP of different types (with a different heterocyclic part) were determined. It was shown that for all of the SPP studied (except for dithiolane SPP), C is almost independent of the heterocyclic part and is determined by the structure of the chromene part of the SPP. In addition to photodegradation, photooxidation takes place as a result of the reaction of the triplet state of the closed form of the SPP with O2 for nitrosubstituted SPP of all types. The value of C is determined by the efficiency of the reaction of isomer X of the colored form with the solvent or impurities, i.e., the lifetime of this isomer.Translated from Izvestiya Akademii Nauk SSSR, Seriya Khimicheskaya, No. 2, pp. 290–298, February, 1990.  相似文献   

5.
Summary The potential, 0, of the diffuse electric layer was determined by the equilibrium liquid film method (1). The method is based on calculating the 0-potential by means of the DLVO theory of the electrostatic disjoining pressure at known concentration,C el of the solution forming the microscopic liquid film and at known thickness,h r of the film. The thickness of the film was measured by the microinterferometric method (7, 8). The calculation of the potential was carrried out by means of the more general eqs. [2] and [3], valid for a wide range ofC el and 0. The dependence of the potential of the diffuse electric layer on the concentration of surface activ agent (surfactant) stabilizing the liquid film was found. It was established that ionogenic SAS show a higher potential than the non-ionogenic ones. The potential of SAS-free solutions was determined — ca. 30 mV.The dependence of the potential of the diffuse electric layer on concentration and kind of electrolyte was also found.A strong effect of pH on 0-potential was observed and the isoelectric points were found. An analysis is made of the 0-potential values obtained by the method of equilibrium liquid film with respect to their similarity to those on the boundary of the bulk liquid.
Zusammenfassung Das Potential 0 der diffusen elektrischen Doppelschicht wurde nach der Methode des flüssigen Gleichgewichtfilms in Schäumen (1) bestimmt. Die Dicke der Filme wurde interferometrisch (7, 8) gemessen.Es wurde die Abhängigkeit des 0-Potentials von der KonzentrationC S des grenzflächenaktiven Stoffes (Schaumfilmstabilisator) untersucht. Die 0 (C S)-Kurve hat am Anfang ein kleines Plateau, danach folgt ein Anstieg bis zu einem Sättigungswert. Dieser Sättigungswert 0 ist für die verschiedenen Tenside unterschiedlich. Nichtionogene Tenside besitzen ein geringes 0, die ionogenen Tenside geben höhere Werte.Es wurde weiterhin der Einfluß der Elektrolytkonzentration auf das 0-Potential untersucht. Eine spezifische Wirkung der Elektrolyte wurde nicht gefunden. Dagegen wurde ein starker Einfluß des pH-Wertes auf das 0-Potential festgestellt. Bei einem bestimmten pH-Wert fällt 0 bis zu Null ab, d. h. ein isoelektrischer Punkt tritt auf. Die an Schaumfilmen gemessenen 0-Werte wurden mit den 0-Werten an der Oberfläche derselben Lösung verglichen.
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6.
The apparent molar volumes V and heat capacities C p, of NaCl, LiCl, NaF, KI, NaBPh4 and Ph4PCl have been determined in solutions of H2O containing up to 40 mass% t-butyl alcohol (TBA) by flow densitometry and flow microcalorimetry. Combination of these results with literature data allows calculation of V and C p, for 16 ions in these mixtures using the assumption that tX(Ph4P+) = tX(BPh 4 ) where X=V or C p and tX is the change in X for a species on transfer from H2O to TBA-H2O mixtures. These are the first reported single ion values for C p, in a mixed solvent. While whole electrolyte volumes and heat capacities show relatively smooth changes with solvent composition, tX(ion) exhibit two well-developed extrema at around 10 and 25 mass% TBA. The shape of the tX(ion) curves shows considerable uniformity among the alkali metal cations and the halide ions but the extrema become more pronounced with increasing size among the tetraalkylammonium ions. These extrema are analogous to those observed in aqueous organic mixtures of surfactants and are probably indicative of microphase transitions in these strongly interacting solvent mixtures.  相似文献   

7.
Torsional potentialV() for the single bond transformation in an extended hexadecane, subjected to elongation, has been determined by molecular mechanics calculations. The stored elastic energy significantly modifies the potentialV(), the conformational energies and the barriers of transition. Apart from the soft torsional coordinate, elastic energy is also dissipated considerably by bond stretching and angle bending. Maximal variations of the valence coordinates occur in the vicinity of the torsional defect and dampen along the chain. At higher elongation, the gauche minimum on the potentialV() disappears and the calculations predict the abrupt gauche to trans transition. The energetics of torsion of a deformed chain are compared with the experimental data on the hydrodynamic extension of polymers in dilute solution by elongational flow. The calculations also provide details of a single bond transformation mechanism at conformational interconversions in a long chain, proposed by Helfand.  相似文献   

8.
The application of MO LCAO methods to molecules containing elements in the higher periods is discussed, especially compounds containing two phenyl rings linked via an oxygen atom. The calculated -electron density is found to agree with the observed electronic absorption spectra, dipole moment, effects of polarity on reactivity, and so on, provided that the wave function used for the heteroatom with n>2 is =c1 npz+ +c2 nd+...; the terms c2 nd... provide correction for the change in the atomic function npz produced by the surrounding atoms. This effect is not important for O, N, and C (first period). The effects of surrounding atoms on npz for the halogen atom have evidently to be considered in computations on the -electron density for any molecule containing such an atom.  相似文献   

9.
Zusammenfassung Die als Schnittpunkt von Volumen-Temperatur-Kurven für Schmelze und Glas ermittelte Glasübergangstemperatur wird als unterste Grenze der Schmelze angesehen. Diese wird entsprechend der Löchertheorie für Flüssigkeiten von Eyring und Hirai als eine mit Leerstellen gesättigte Mischung aufgefaßt.Es wird eine Verdünnungsentropie S1 bestimmt, für die der athermische Ansatz von Flory und Huggins benutzt, und eine Verdünnungsenthalpie H1, für die ein eigener Ansatz abgeleitet wird, der statt der üblichen mittleren Koordinationszahl z einen geometrischen Parameter a enthält. Dieser scheint realistischer die Größe und Gestalt der Mischungspartner zu berücksichtigen. Mit Hilfe der beiden Größen S1 und H1 sowie Volumen- und Enthalpiefunktionen lassen sich Ausdrücke für die Änderung des Ausdehnungskoeffizienten * und der Molwärme Cp bei der Glastemperatur entwickeln. Diese ermöglichen eine Berechnung des spez. freien Volumens 1 * und des geometrischen Parameters a für 11 verschiedene Hochpolymeren. Dabei ergibt sich, daß a offenbar bei der Glastemperatur eine Konstante ist, während 1 * nur sehr grob als Konstante angesprochen werden kann. Ein mittlerer Wert von ¯ 1 * =0,0235 stimmt aber sehr gut mit dem von Williams, Landel und Ferry viskosimetrisch bestimmten Wert von ca. 0,025 überein. Diese Übereinstimmung läßt den Schluß zu, daß im Sinne der Löchertheorie nur die Leerstellen als freies Volumen anzusprechen sind und für translatorische Bewegungsmechanismen zur Verfügung stehen, nicht aber das Schwingungsausdehnungsvolumen.Die Inkonstanz von 1 * bei genauerer Betrachtung zeigt aber, daß offenbar bei der Glastemperatur kein iso-freier Volumenzustand herrscht. Die gleiche Feststellung trifft auch Miller auf Grund viskosimetrischer Untersuchungen. Die Abweichungen der Meßdaten von der Simha-Boyer-Gleichung * · Tg=k lassen sich dadurch erklären, daß k gar keine Konstante ist, sondern eine Funktion von 1 * . Dieses zeigt aber, daß Stoffe mit beweglicheren Kettenmolekülen ein kleineres 1 * als Stoffe mit steiferen Kettenmolekülen besitzen. Die gleiche Beobachtung wird bei der analogen Cp-Beziehung gemacht. Das freie Volumen bei der Glastemperatur 1 * ist demnach ein Maß für die Molekülsteifigkeit. Ferner gelingt es, Leerstellenvolumina von verschiedenen Hochpolymeren auszurechnen. Die Ergebnisse bestätigen vollauf die Annahme von Frenkel, daß die Leerstellen die Größe von kleinen Atomen haben und im Prinzip nichts mit der Molekülgröße zu tun haben.
Summary The glass transition temperature, the intersection of volume-temperature-curves for melt and glass, is considered as lowest limit of the melt. In accordance with the hole-theory of Eyring and Hirai for liquids same is interpreted as a mixture saturated with holes.There is being defined an entropy of dilution S1 for which the athermal concept of Flory and Huggins is taken, and an enthalpy of dilution H1 for which an own concept is derived with a geometrical parameter a instead of the usual mean coordination number z. This parameter seems to consider more realistically the size and shape of the mixing components. By means of S1 and H1 as well as the functions of volume and enthalpy expressions for the change of the expansion coefficient * and the molar heat Cp at glass temperature can be evolved. Thus a calculation of the specific free volume 1 * and of the geometrical parameter a is rendered possible for 11 high polymers. It can be stated that at glass temperature a evidently is a constant while 1 * just roughly can be called a constant. A mean value of ¯ 1 * =0.0235 corresponds, however, very well with the value of about 0.025 which was found by Williams, Landel and Ferry by viscosimetric measurements. In consideration of this conformity it can be concluded that in accordance with the hole-theory only the holes can be defined as free volume and that they are available for translationmechanisms and not the vibration-expansion-volume.When going into the matter it can be seen from the inconstancy of 1 * that evidently no iso-free volume state is given at the glass temperature. The same conclusion is drawn by Miller on account of viscosimetric measurements. The deviation of the data from the Simha-Boyer-equation * · Tg=k can be explained by the statement that k is no constant but a function of 1 * . This shows that material with flexible chain molecules have a smaller 1 * than material with less mobile chain molecules. The same appearance can be observed with the analogous Cp-relation. Consequently the free volume at the glass temperature 1 * is a measure for the stiffness of the molecules. Moreover it is possible to calculate hole volumes of various high polymers. The results confirm to a full extent Frenkel's assumption that the holes have the size of small atoms and, in principle, have nothing to do with the size of the molecules.


Herrn Dr.H. Wilski, Frankfurt-Höchst, und meinem Kollegen Herrn Dr.K. H. Illers habe ich für die Überlassung einiger Meßdaten herzlich zu danken.

Meinem Kollegen Herrn Dr.K. Apel danke ich besonders herzlich für die Programmierung und Durchführung von Rechnungen auf einem Tisch-Computer.  相似文献   

10.
One- or two-step reactions of potassium and rubidium fullerides with composition Mk C60 (M = K, Rb; k = 3—6) and K6C60 + m K mixtures (m = 1, 3) with anhydrous salts MCl3 (M = La, Pr, Nd, Sm, Gd, Tb, Yb, Lu, Y, Sc) and YbI2 in a toluene—THF medium afforded heterometallic fullerides M3–nMnC60 (n = 1—3). Among these compounds, substituted fullerides with composition M2MC60 (M = Yb, Lu, Sc) display superconducting properties with critical temperatures of 14—20 K.Published in Russian in Izvestiya Akademii Nauk. Seriya Khimicheskaya, No. 8, pp. 1623–1628, August, 2004.  相似文献   

11.
The dependence of the quantum yield of photogeneration of singlet oxygen with aluminum sulfophthalocyanines on the degree of their sulfonation was studied. Experiments showed that Fotosens preparation containing, on the average, about three sulfo groups in the macroring in aqueous buffer solution (pH 7.4) exists in the monomeric form and sensitizes singlet oxygen with a quantum yield 0.42±0.06. Aluminum tetra-4-sulfophthalocyanine forms dimers, and correspondingly is lower: 0.22±0.03. Sulfonated aluminum phthalocyanine containing, on the average, about two sulfo groups in the macroring is aggregated to a significant extent. Addition of Triton X-100 detergent results in partial deaggregation of the dye, and increases from 0.01 to 0.15±0.02. In the series including previously unknown aluminum phthalocyanines containing residues of phosphonic acids or their esters, and also aluminum and zinc octacarboxyphthalocyanines, the influence of the dye structure on the quantum yield of generation of singlet oxygen suggests participation of axial hydroxy groups in associate formation. These associates are not manifested spectroscopically and generate singlet oxygen inefficiently. The quantum yields for the monomers and associates are 0.3 and 0.1, respectively.  相似文献   

12.
Crystals of the -complex [C4H8N2(C3H5)4]2+[CuCl2] 2 (I) were prepared by ac electrochemical synthesis from copper and N,N,N,N-tetraallylpiperasinium chlorides in alcohol solution. Similar synthesis with the use of the metal and N,N,N,N-tetraallylpiperasinium bromides yielded the complex [C4H8N2(C3H5)4]2+[CuBr3]2– (II). Structures I and II were studied by X-ray diffraction (DARCh automated single-crystal diffractometer, MoK radiation). Crystals of I are triclinic, space group P1¯, a = 8.650(3) Å, b = 7.572(2) Å, c = 8.095(3) Å, = 100.45(2)°, = 83.91(2)°, = 99.89(2)°, V = 512.1(6) Å3, Z = 1. Crystals of II are orthorhombic, space group Pn21 a, a = 17.673(3) Å, b = 14.369(6) Å, c = 8.244(2) Å, V = 2093(2) Å3, Z = 4. In structure I, the potentially tetradentate N,N,N,N-tetraallylpiperasinium cation uses two centrosymmetric allyl groups for bonding with copper atoms, whose environment is completed to the trigonal-planar coordination with the chlorine atoms. The [C4H8N2(C3H5)4]2+[CuCl2] 2 groups are joined into a three-dimensional framework by weak hydrogen bonds. The inorganic fragment CuCl 2 is partially disordered, which appears as splitting of the positions of the copper atom and one of the chlorine atom. In compound II, the inorganic fragment occurs as an unusual trigonal-planar CuBr2– 3 anion; the N,N,N,N-tetraallylpiperasinium cation is not involved in metal coordination.  相似文献   

13.
Summary The experimental data available on the thermodynamic functions 0 forMnHF hydrofluorides [M=Li, Na, K, Rb, Cs, NH4, Ag(I) and Tl(I);n=1–3] have been evaluated additively. The unknown values of 0 forn=0÷7 are predicted.
Additive Voraussagen der thermodynamischen Funktionen von Hydrogenfluoriden (Kurze Mitt.)
Zusammenfassung Die vorhandenen experimentellen Daten über die thermodynamischen Funktionen 0 von HydrogenfluoridenMnHF [M=Li, Na, K, Rb, Cs, NH4, Ag(I) und Tl(I);n=1–3] werden linear ausgeglichen und die fehlendenden Werte für 0 mitn=0÷7 vorausgesagt.
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14.
The structure of the inclusion complex formed between naringin (naringenin-7-O--neohesperidoside) and-cyclodextrin (BCD) was studied in detail by UV and NMR spectroscopic techniques and potentiometry. A binding constant value of 1016±150M–1 was arrived at from UV studies. Potentiometric studies showed that pK values of 4-OH and 5-OH were affected by and-cyclodextrins. One-dimensional difference NOE and spin-lattice relaxation time (T 1) measurements indicated that the aglycone protion was affected more than the neohesperidoside portion. TheT 1 values analysed for local motions indicated that c values of complexed naringin was higher than that of free naringin. The internal rotation calculated for different groups showed i values for the phenolic and dihydrobenzopyran portion decrease by a factor of 2. Also a value of 0.12–0.17 observed for the aglycone portion indicated that the coupling between guest and host is weak. All the studies have shown that the disposition in which the phenol group at 2 is inside the BCD cavity with 4-keto and 5-OH hydrogen bonded to the secondary hydroxyl groups at the rim of the wider end of the BCD cavity is the most probable one.  相似文献   

15.
The permeability of styrene-butadiene block copolymer foils with different composition prepared by casting and pressing has been investigated for the gases Ar, CO2, and CH4 at pressure difference of 400 mbar and at the temperature range 298 T [K] 333.The permeation process can be described by the solution diffusion mechanism. The diffusion coefficients decrease in the sequence of the gases Ar, CO2, and CH4 and the solubility coefficients increase in the sequence Ar, CH4, CO2.The dependence of the permeability on the composition of the block copolymer can be interpreted by the help of percolation theory and the effective medium theory. It follows the critical volume fraction of the percolation of the transport phase PB c (= 0,23) and the coordination numberz (= 4) giving an information concerning the multiphase structure of the block copolymer.Presented in part at the 33rd Annual Meeting of the Colloid-Gesellschaft, Graz, Austria, September 14–16, 1987.  相似文献   

16.
A procedure for the synthesis of uranyltricarbonatetetrarubidium Rb4UO2(CO3)3 was developed. Its crystal structure was determined by X-ray diffraction analysis: space group C2/c; a=10.778(5) , b=9.381(2) , c=12.509(3) . =94.42(3)°, Z=4; 1178 independent reflections, R=0.0662.__________Translated from Koordinatsionnaya Khimiya, Vol. 31, No. 5, 2005, pp. 387–390.Original Russian Text Copyright © 2005 by Chernorukov, Mikhailov, Knyazev, Kanishcheva, Zamkovaya.  相似文献   

17.
The structure and the relative stability of the N-, C-, and C-anions of pyrrole, its mono- and dimethyl derivatives, and their adducts with carbon disulfide were studied by the ab initio method (MP2/6-31+G*//RHF/6-31+G*). The substituent effect on the reaction path is considered. For unsubstituted pyrrole, the stability of the adducts decreases in the series C > N > C. The stability of the N-adducts decreases considerably in the presence of the methyl groups introduced into the -position in view of steric interactions. Possible reasons for the experimentally observed formation of the thermodynamically less stable N-adduct of the unsubstituted pyrrole and for the absence of N-adducts in reactions of the methyl derivatives with CS2 are discussed.  相似文献   

18.
Summary Formation constants of the complexes of Ag(I) with 2-pyridine-carboxylic acid (Hpic) were determined by the potentiometric method: 01=36, 02=537. It was shown by IR spectroscopy that the complexation of Ag(I) ions in acetonitrile proceeds without the formation of Ag-O bond and the complexes have the following forms: AgHpic + and Ag(Hpic) 2 + . Oxidation of Ag(Hpic) 2 + at the potential =1850 mV vs. NHE resulted in the complex Ag(Hpic) 2 2+ . The formal potentialE f 0 =1.772 V vs. NHE of the system Ag(Hpic) 2 2+ +eAg(Hpic)++Hpic was determined by chronovoltamperometry, while the formal potentialE f 0 =1.841 V vs. NHE of the system Ag(Hpic) 2 2+ +eAg(Hpic) 2 + was calculated. Properties of the system in water and acetonitrile were compared.
Charakteristik des Ag(II)/Ag(I)-Systems in Gegenwart von 2-Pyridincarbonsäure in Acetonitril
Zusammenfassung Es wurden die Bildungskonstanten der Komplexe von Ag(I) mit 2-Pyridincarbonsäure (Hpic) mittels Potentiometrie bestimmt: 01=36, 02=537. Die IR-Spektren bewiesen, daß die Komplexierung von Ag(I)-Ionen über die Ausbildung einer Ag-O-Bindung verläuft, wobei die Komplexe die folgenden Formeln besitzen: AgHpic + und Ag(Hpic) 2 + . Die Oxidation von Ag(Hpic) 2 + beim Potential =1850 mV gegenüber NHE ergab den Komplex Ag(Hpic) 2 2+ . Das formale PotentialE f 0 =1.772 V (gegenüber NHE) des Systems Ag(Hpic) 2 2+ +eAg(Hpic)++Hpic wurde mittels Chronovoltamperometrie ermittelt, während das formale PotentialE f 0 =1.841 V (gegenüber NHE) des Systems Ag(Hpic) 2 2+ +eAg(Hpic) 2 + berechnet wurde. Außerdem wurden die Eigenschaften der Systeme in Wasser und Acetonitril verglichen.
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19.
Density measurements of water-dodecyltrimethylammonium bromide (DTAB)-alcohol ternary systems as a function of alcohol and surfactant concentrations were carried out at 25°C. The alcohols were propanol (PrOH), 2-propanol (2-PrOH) and hexanol (HexOH). The apparent molar volume V,R of alcohols have been calculated and the standard (infinite dilution) partial molar volumes of alcohols V R at each surfactant concentration were obtained by means of a least squares fit of V,R vs. the alcohol concentration. The V R vs. surfactant concentration curves have been rationalized in terms of the partial molar volume of alcohol in the aqueous V f and the micellar V b phases and the distribution constant of alcohol between the aqueous and the micellar phases K. The V b values for PrOH and HexOH together with those of butanol and pentanol previously reported satisfy the additivity rule giving a methylene group contribution of 16.7 cm3-mol–1 which is identical to that reported in the literature from the study of pure liquid alcohols. No difference between V b for PrOH and 2-PrOH has been found. From density data of water-alcohol and water-surfactant binary systems and of water-surfactant-alcohol ternary system, the apparent molar volume of the surfactant in the water-alcohol mixed solvent V,S have been calculated as a function of the surfactant concentration and of the mixed solvent composition. The effect of the alkyl chain length of the alcohols and the effect of isomerization of the alcohols on the V,S vs. surfactant concentration trends have been analyzed.  相似文献   

20.
The crystal structures of two polysulfide phases HoS1.885(5) (I) and HoS1.863(8) (II) were determined; the integer stoichiometric ratio was found to be Ho8S15. The data were collected on an Enraf-Nonius CAD-4 automatic diffractometer using the standard procedure (MoK, graphite monochromator, an absorption correction applied based on -scan data). Crystal I: space group P4/nmm, a = 3.820(1), c = 7.840(3) , V = 114.40(6) 3, Z = 2 for the composition HoS1.885(5), d calc = 6.542 g/cm3, R = 0.0520 for 184 unique reflections with Ihkl > 2 I; crystal II: space group P21/m, a = 10.961(2), b = 11.465(2), c = 10.984(2) , = 91.27(3)°, V = 1380.0(4) 3, Z = 24 for the composition HoS1.863(8), d calc = 6.486 g/cm3, R = 0.0596 for 5354 unique reflections with Ihkl > 2 I. In both compounds, the Ho atoms are surrounded by 9 (8+1 for three atoms in II) S atoms forming monocapped square antiprisms. The Ho–S distances vary from 2.717 to 3.067 irrespective of the type of ion [S2– or (S2)2–]; the maximal distance to the atoms completing the coordination is 3.684 . The compounds have PbFCl type structures composed of ...(S2)2–...Ho3+...S2–...S2–...Ho3+...(S2)2–... layer packets differently oriented in space relative to the unit cell axes. The S2–...S2– and S2–...(S2)2– interlayer distances are mostly shorter than the sum of the ionic radii and vary within the limits of 3.331-3.558 and 3.029-3.784 for the first and second types, respectively. For I, the calculated site occupancies and densities are given depending on the composition Ho-S2-x (x = 0.25-0); for II, the most probable formulas of rational compositions in the same range of x are presented.  相似文献   

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