Structure and vibrations of Ga(n)N(n) (n = 3-10) clusters

The structure and harmonic vibrations of Ga(n)N(n) (n = 3-10) clusters have been investigated using the B3LYP (Becke 3-parameter-Lee-Yang-Parr) density functional theory. All structures are found to be cumulenic D(nh) rings (equal bonds, alternating angles), with one intense out of plane mode and three infrared-active degenerate modes, of which the highest one is extremely intense and asymptotically increases to 1029 cm(-1) for n = 10. Comparisons with C2n, B(n)N(n), and Al(n)N(n) clusters, the structure and bonding type for the Ga(n)N(n) (n=3-10) clusters are consistent with those of the C2n (n = 3, 5, 7, ...) clusters, the B(n)N(n) (n = 3-10), and Al(n)N(n) (n = 3-9) clusters.     

The thermal dissociation of some carbonate minerals

Detailed differential thermal studies on mixtures ofnatural carbonate minerals have confirmed the peak-temperature shifts recently reported for mixtures ofsynthetic carbonates and have established that such shifts can be attributed entirely to dilution effects. The exception, where magnesite in the presence of siderite maintains its peak position, is due simply to the fact that both minerals give similarly sized peaks at approximately the same temperature.

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Zusammenfassung Eingehende differentialthermische Untersuchungen von Gemischen natürlicher Karbonatmineralien zeigten ähnliche Spitzentemperaturverlagerungen wie kürzlich bei Gemischen von künstlichen Karbonatgemischen beobachtet wurden. Solche Verlagerungen sind ausschließlich Dilutionserscheinungen zuzuschreiben. Magnesit behielt zwar in Gegenwart von Siderit seine Spitzenpositionen, wofür jedoch der Umstand verantwortlich ist, daß beide Mineralien ähnliche und bei gleichen Temperaturen erscheinende Spitzen besitzen.

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Résumé L'étude de mélanges de carbonatesnaturels par les procédés thermiques différentiels a confirmé l'observation faite récemment d'un déplacement de la température au sommet du pic pour des mélanges de carbonatessynthétiques. On attribue ces déplacements entièrement aux effets de dilution. La magnésite en présence de sidérite constitue une exception. Dans ce cas, la position du pic reste inchangée du fait que ces deux minéraux donnent des phénomènes sensiblement identiques presque à la même température.

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, , , (1) , , . , , (1), , .

     

Oscillatory behavior in the reaction of 3-alizarin-sulfonic acid sodium salt with acidic bromate

Uncatalyzed and catalyzed oscillatory behavior in the redox potential in the oxidation of 3-alizarin-sulfonic acid sodium salt with acidid (H₂SO₄) bromate is reported. Optimum and boundary conditions for each reactant exhibiting oscillatory behavior have been studied and a probable mechanism is suggested.

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- 3-- (H₂SO₄) . , .

     

Methods to determine the temperature dependence of the pre-exponential factor of the Arrhenius equation from thermogravimetric data

The well-known methods of Coats-Redfern, Freeman-Carroll, and Achar et al. are modified to include the temperature dependence of the pre-exponential factor in the Arrhenius expression for the rate constant. These modifications serve to cast these methods into their most general Arrhenius form. Suggestions are given regarding various numerical methods for extracting the temperature dependence of the preexponential factor from thermogravimetric and derivative thermogravimetric data.

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Zusammenfassung Die bekannten Methoden von Coats-Redfern, Freeman-Carroll sowie Achar und Mitarbeiter wurden auf solche Weise modifiziert, dass sie die Temperaturabhängigkeit des präexponentiellen Faktors in der Arrhenius-Gleichung für die Geschwindigkeitskonstante enthalten. Durch diese Abänderungen werden diese Methoden in ihre ganz allgemeine Arrhenius-Form überführt. Vorschläge betreffs verschiedener numerischer Methoden zur Ermittlung der Temperaturabhängigkeit des präexponentiellen Faktors aus thermogravimetrischen und derivierten thermogravimetrischen Angaben werden gemacht.

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Résumé Les méthodes bien connues de Coats-Redfern, Freeman-Carroll et Achar et al. ont été modifiées afin de tenir compte du fait que le facteur préexponentiel donnant la constante de vitesse dans l'expression d'Arrhenius est une fonction de la température. Ces modifications permettent d'exprimer l'équation d'Arrhenius sous une forme plus générale. Plusieurs méthodes numériques sont proposées pour exprimer la relation du facteur préexponentiel avec la température à partir des données TG et des courbes TG dérivées.

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-, - ** ., ** . ** , . , .

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The authors wish to thank V. E. Anderson for some helpful discussions.

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Research sponsored by the Energy Research and Development Administration under contract with Union Carbide Corporation.     

Comparison of the growth patterns of Si(n) and Ge(n) clusters (n = 25-33)

We performed an unbiased search for low-energy structures of medium-sized neutral Si n and Ge n clusters ( n = 25-33) using a genetic algorithm (GA) coupled with tight-binding interatomic potentials. Structural candidates obtained from our GA search were further optimized by first-principles calculations using density functional theory (DFT). Our approach reproduces well the lowest-energy structures of Si n and Ge n clusters of n = 25-29 compared to previous studies, showing the accuracy and reliability of our approach. In the present study, we pay more attention to determine low-lying isomers of Si n and Ge n ( n = 29-33) and study the growth patterns of these clusters. The B3LYP calculations suggest that the growth pattern of Si n ( n = 25-33) clusters undergoes a transition from prolate to cage at n = 31, while this transition appears at n = 26 from the PBE-calculated results. In the size range of 25-33, the corresponding Ge n clusters hold the prolate growth pattern. The relative stabilities and different structural motifs of Si n and Ge n ( n = 25-33) clusters were studied, and the changes of small cluster structures, when acting as building blocks of large clusters, were also discussed.     

Heavy group 14 1,(n+2)-dimetallabicyclo[n.n.n]alkanes and 1,(n+2)-dimetalla[n.n.n]propellanes: are they all realistic synthetic targets?

[n.n.n]Propellanes and bicyclo[n.n.n]alkanes (1相似文献   

Structure and vibrations of AlnNn (n = 3-9) clusters

The structure and harmonic vibrations of Al(n)N(n) (n = 3-9) clusters have been investigated using the B3LYP (Becke 3-parameter-Lee-Yang-Parr) density functional theory. All structures are found to be cumulenic D(nh) rings (equal bonds, alternating angles), with one intense out-of-plane mode and three infrared-active degenerate modes, of which the highest one is extremely intense and asymptotically increases to 1217 cm(-1) for n = 9. Comparisons with C2n clusters and B(n)N(n) clusters, the structure and bonding type for the Al(n)N(n) clusters are consistent with those of the C2n (n = 3, 5, 7, ...) clusters and the B(n)N(n) clusters.     

Structure and vibrations of BenOn (n=3-10) clusters

The structure and harmonic vibrations of Be(n)O(n) (n=3-10) clusters have been investigated using density functional theory. All structures are found to be cumulenic D(nh) rings (equal bonds, alternating angles), with one intense out of plane mode and three infrared-active degenerate modes, of which the highest one is extremely intense and asymptotically increases to 1597 cm(-1) for n=10. Comparisons with C(2n) clusters and B(n)N(n) clusters, the structure and bonding type for the Be(n)O(n) clusters are consistent with those of the C(2n) (n=3, 5, 7, ...) clusters and the B(n)N(n) clusters.     

Calculation of recombination rate constants in (H2?O2) system

Rate constants of the three-body recombination for the elementary three-molecule stages in hydrogen oxydation have been calculated.

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, .

     

Analysis of the heat capacities of group IV chalcogenides using debye temperatures

The low temperature heat capacities of 13 group IV chalcogenides are examined. The heat capacity of crystals with largely isotropic structure (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) can be represented within ±3% by a three-dimensional Debye function ( ₃=205, 230, 175, 225, 150 and 130, respectively). The heat capacity of crystals with anisotropic structures (GeS, GeSe, SnS, GeS₂ and SnS₂) could only be represented by pairs of two-dimensional Debye functions for the longitudinal and transverse lattice vibrations (error ±0.5 to 3%; ₂ (l)=505, 345, 400, 705, 480 and 570, respectively, and ₂ (t)=200, 185, 160, 175, 100 and 265, respectively).Since the two-dimensional Debye function has not been tabulated in detail, we offer in the appendix a five place table of it. Raman and infrared data support this analysis.

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Zusammenfassung Die Wärmekapazität bei niedrigen Temperaturen wurde für 13 Chalcogenide der Gruppe IV untersucht. Die Wärmekapazität der Kristalle von hauptsächlich istotroper Struktur (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) kann innerhalb von ±3% durch eine. dreidimensionale Debye-Funktion dargestellt werden ( ₃=205, 230, 175, 225, 150 bzw. 130). Die Wärmekapazität von Kristallen anisotroper Struktur (GeS, GeSe, SnS, GeS₂, GeSe₂ und SnS₂) konnte für longitudinale und transversale Gittervibrationen nur durch Paare zweidimensionaler Debye-Funktionen dargestellt werden (Fehler: ±0,5 bis 3%; ₂ (l)=505, 345 400, 705, 480 bzw. 570 und ₂(t)=200, 185, 160, 175, 100 bzw. 265).Da die zweidimensionale Debye-Funktion nicht in allen Einzelheiten tabellarisiert worden ist, wird im Anhang eine fünfstellige Tafel dafür gegeben. Raman- und Infrarot-Angaben bestätigen diese Analyse.

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Résumé On a examiné les capacités calorifiques à basses températures de 13 chalcogénure du groupe IV. Les capacités calorifiques des cristaux de structures principalement isotrope (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) peuvent être représentées à ±3%, par une fonction Debye à trois dimensions ( ₃=205, 230, 175, 225, 150 et 130 respectivement). Les capacités calorifiques des cristaux à structures anisotropes (GeS, GeSe, SnS, GeS₂, GeSe₂ et SnS₂) ne peuvent être représentées que par des paires de fonctions Debye à deux dimensions, pour les vibrations du réseau longitudinales et transversales (erreur de ±0,5 à 3%; ₂(l)=505, 345, 400, 705, 480 et 570, et ₂,(t)=200,185, 160, 175, 100 et 265).Comme il n'existe pas de tableaux détaillés pour la fonction Debye à deux dimensions les auteurs donnent en appendice un tableau à cinq positions. Des données Raman et infrarouges sont fournies à l'appui de cette analyse.

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13 IV. (GeTe, SnSe, SnTe, PbS, PbSe, PbTe) ±3% ( ₃=205, 230, 175, 225, 150 130, ). (GeS, GeSe, SnS, GeS₂, GeSe₂, SnS₂) ( ±0.5 3%; ₂ (.)=505, 345, 400, 705, 480 570 , ₂ (.)=200, 185, 160, 175, 100 265). , . .

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The authors would like to acknowledge the help of Professor H. H. Hollinger and Professor M. S. Krishnamoorty with the solution of the two-dimensional Debye function. The authors would also like to acknowledge the support of this work in part by the National Aeronautics and Space Administration and by the National Science Foundation, Polymer Programs, Contract No. DMR 78-15279.     

Magnetism of cyano-bridged Ln3+-M3+ complexes. Part II: one-dimensional complexes (Ln3+ = Eu, Tb, Dy, Ho, Er, Tm; M3+ = Fe or Co) with bpy as blocking ligand

The reaction of Ln(NO3)3(aq) with K3[Fe(CN)6] or K3[Co(CN)6] and 2,2'-bipyridine in water/ethanol led to 13 one-dimensional complexes: trans-[M(CN)4(mu-CN)2Ln(H2O)4(bpy)]n.4nH2O.1.5nbpy (Ln = Eu3+, Tb3+, Dy3+, Ho3+, Er3+, Tm3+, Lu3+; M = Fe3+, Co3+). The structures for [EuFe]n (1), [TbFe]n (2), [DyFe]n (3), [HoFe]n (4), [ErFe]n (5), [TmFe]n (6), [LuFe]n (7), [EuCo]n (8), [TbCo]n (9), [DyCo]n (10), [HoCo]n (11), [ErCo]n (12), and [TmCo]n (13) have been solved: they crystallize in the triclinic space group P and are isomorphous. They exhibit a supramolecular architecture created by the interplay of coordinative, hydrogen bonding, and pi-pi interactions. A stereochemical study of the eight-vertex polyhedra of the lanthanide ions, based on continuous shape measures, is presented. The Ln3+-Fe3+ interaction is antiferromagnetic in [DyFe]n and [TbFe]n. For [EuFe]n, [HoFe]n, [ErFe]n, and [TmFe]n, there is no sign of any significant interaction. The magnetic behavior of [DyFe]n suggests the onset of weak long-range ferromagnetic ordering at 2.5 K.     

Zur Frage der Quantitativen Differentialthermoanalyse Cristobalithaltiger Staubproben

Zusammenfassung Mit einer DTA-Anlage eigener Entwicklung werden an Cristobalitproben verschiedener Herkunft und Entstehungsgeschichte Umwandlungstemperatur und Wärmetönung der --Inversion bestimmt. Die dabei gefundene Beziehung zwischen diesen beiden Größen ermöglicht unter gewissen Bedingungen die Ermittlung des Cristobalitgehaltes einer Staubprobe.

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Temperature and heat of the --inversion in christobalite samples of various origin and way of production were measured with a self-constructed DTA-apparatus. A relationship was found between temperature and heat of reaction, which in certain circumstances enables to determine the christobalite content in dust samples.

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Résumé Détermination, à l'aide d'une installation d'ATD personnelle, de la température et de la chaleur de transformation de l'inversion - de divers échantillons de cristobalite d'origine et de préparation différentes. Une relation est apparue entre ces deux grandeurs permettant de déterminer, sous certaines conditions, la teneur en cristobalite d'un échantillon de poussière.

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– , . , .

     

FT-Raman Spectra of o-, m-, and p-Nitrophenol Included in Cyclodextrins

FT-Raman spectra of o-, m-, and p-nitrophenol included in -cyclodextrin (CD), -CD, hydroxypropyl (HP) -CD, andsulfated -CD were recorded. The phenyl (C=C) band of o- and p-nitrophenol in the CD inclusion complexes was shifted to higher wavenumber thanthat of pure o- and p-nitrophenol,whereas the phenyl (C=C) band of m-nitrophenol in the CD inclusion complexes was shifted to lower wavenumber than that of pure m-nitrophenol. The ring CH peak of o-nitrophenol in the CD complexes was shifted to higher wavenumber than that of pure o-nitrophenol, whereas the ring CH peak of m- and p-nitrophenol in the CD complexes was shifted to lower wavenumber than that of pure m- and p-nitrophenol.     

Properties of molten alkali metal trifluoroacetates

The CF₃COOK-CF₃COONa phase diagram was studied by DTA between 100% and 50 wt. % CF₃COOK; the thermal decomposition of CF₃COONa-rich samples prevents the complete determination of the phase diagram. Two eutectics were found:E ₁ at 89.5 wt. % CF₃COOK andE ₂ at 62 wt. %, with melting points at 122–123 and 112–113, respectively, representing a temperature approximately 30 lower than the m. p. of pure CF₃COOK (140.5). The presence of a compound between these two eutectics is not formally established, but is probable at about 85 or 87 wt. % CF₃COOK, melting at 124–125. DTA has shown that the fused mixtures solidify into a metastable state, the phase diagram of which presents a labile eutectic at 75 wt. % CF₃COOK, melting at 88.

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Zusammenfassung Das CF₃COOK-CF₃COONa Phasendiagramm wurde mittels DTA, zwischen 100 und 50 Gew. % CF₃COOK untersucht; die thermische Zersetzung CF₃COONa-reicher Proben macht die Bestimmung des vollständigen Phasendiagramms unmöglich. Zwei Eutektika wurden gefunden:E ₁ bei 89.5 Gew. % CF₃COOK undE ₂ bei 62 Gew. %, mit den entsprechenden Schmelzpunkten bei 122–123 und 112–113, welche bei um etwa 30 niedrigeren Temperaturen liegen als der Schmelzpunkt des reinen CF₃COOK (140.5). Die Existenz einer Verbindung zwischen diesen beiden Eutektika wurde zwar nicht genau bewiesen, sie liegt aber wahrscheinlich bei etwa 85 oder 87 Gew. % CF₃COOK und schmilzt bei 124–125. Mittels der DTA konnte nachgewiesen werden, daß die geschmolzenen Gemische in einen metastabilen Festkörperzustand übergehen, dessen Phasendiagramm ein labiles Eutektikum bei 75 Gew. % CF₃COOK mit einem Schmelzpunk bei 88 aufweist.

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Résumé Le diagramme de phases CF₃COOK-CF₃COONa a été établi par ATD entre CF₃COOK et le mélange à 50% poids; la décomposition thermique des échantillons riches en CF₃COONa empÊche la détermination complète du diagramme de phases. On observe deux eutectiques:E ₁ à 89.5 % poids en CF₃COOK etE ₂ à 62% poids, fondant respectivement à 122–123 et 112–113, ce qui représente un abaissement d'environ 30 C par rapport au P. F. de CF₃COOK pur (140.5). L'existence d'un composé entre ces deux eutectiques n'a pu Être montrée formellement. Il se situe vraisemblablement vers 85 ou 87 % poids en CF₃COOK et fond à 124–125. L'ATD a montré que les mélanges fondus se solidifient dans un état métastable, dont le diagramme de phases présente un eutectique labile à 75% poids en CF₃COOK fondant à 88.

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CF₃COOK—OF₃COONa CF₃COOK 100 50 .%. CF₃COONa, . :E ₁ CF₃COOK 89,5 .% ₂-62 .% 122–123 112–113, 30 , . . CF₃COOK (140,5). , , , CF₃COOK 85 87 .% 124–125. , , CF₃COOK 75 .% 88.

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This paper is based on part of the Dissertation (No. 1721) of R. Dallenbach, University of Geneva.

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Thanks are due to Professor R. Monnier and Dr. J. J. Duruz for useful discussions.     

Formation and Photodissociation of Transition Metal-Sulfur Binary Cluster Ions

Transition metal-sulfur binary cluster ions were produced by direct laser ablation and analyzed with the first stage time-of-flight mass spectrometer (TOF-MS). It was found that the distribution of the strong peaks of the stable cluster ions in the TOF-MS were not appreciably affected by the composition of the sample. The composition of the most stable metal-sulfur cluster ions, M_nS_m are different for various transition metals: Cu, n = 2m + I and n = 2m; Zn, m = n; Mn, m = n; Fe, m = n, m = n ?1 and m = n ? 2; Co, m = n ? 1, m = n ? 2, m = n ? 3, m = n ? 4 and m = n ? 5; Cr, m = n and m = n + 1; Ta, m = n + 1 and m = n + 2. Cluster ions can be selected by a mass gate, and photolyzed by an excimer laser. The photodissociation product ions were analyzed with the second stage TOF-MS. These product ions were mainly the more stable cluster ions as those given in the first stage TOF-MS.     

Gamma-ray tables for neutron fast neutron and photon activation analysis

In the past several years, a number of gamma-ray tables have been published. All of the tables limit themselves to those nuclides formed in (n, γ) reactions or at most to a few of the more prominent (n, 2n) products. A number of investigators are developing activation analysis methods using fast neutrons or photons. These investigations have been hampered by the lack of tables of gamma-rays of those nuclides that can be formed by (n, 2n), (n, p), (n, α), (n, n′) and (n, d) reactions. Since (γ, n) yields the same product as (n, 2n) the table would also be useful to photon activation studies. The authors have compiled such a table. Section II: list of the gamma-rays for all isotopes in order of increasing energy will be published in the J. Radioanal. Chem., 25 (1975) No. 2.     

同系能级因子的三个新形式及其与以往各因子间的关系

用差分方程法推导并得到同系能级因子的三个新的形式 :xk =2n +8n+4.5sink-122n+1 π ,xk =2n +8n+4.5sin kπ2n+1 ,xk =sin kπ2n+1 ,k =1 ,2 ,… ,n .(n为同系序数 ,k为能级序数 ) ,并探讨了它们与以往各因子之间的关系。     

Heat capacity studies of formation of micelle-like structure in aqueous solutions of some alkane polyols

Some polyols show micellar behavior in aqueous solutions at concentrations greater than the critical micellar concentration (cmc). The 1,2-alkanediols (C(n)H(2n+2)O2 with n=5,6,7), the 1,2,3-alkanetriols (C(n)H(2n+2)O3 with n=7,8,9), and the geminated alkanetriols (C(n)H(2n+2)O3 with n=8 and 9) are investigated by microcalorimetric techniques. Only the 1,2-hexanediol (n=6), the 1,2,3-octanetriol (n=8), and the 2,2-dihydroxymethyl 1-heptanol (n=9) possess, in aqueous solutions, an organized structure above the critical micellar concentration (cmc). The 1,2-pentanediol (n=5) and the 1,2,3-heptanetriol (n=7) would form weak associations, whereas the 2,2-dihydroxymethyl 1-hexanol (n=8) does not form any associations even at large concentration. The 1,2-heptanediol (n=7), being only very slightly soluble even at a temperature of 30 degrees C, could not be studied. The 1,2,3-nonanetriol (n=9) is not soluble at temperatures between 20 and 35 degrees C. The critical micellar concentrations are determined by specific heat capacity methods. The passage from the dispersed environment to the organized environment gives a constant quantity of specific heat capacities (about 50 JK(-1)mol(-1)) only for the 1,2-hexanediol (n=6), the 1,2,3-octanetriol (n=8) and the 2,2-dihydroxymethyl 1-heptanol (n=9), which form true micelles. Structural effects of these systems are discussed.     

Sulfur resistance of Pd complexes with nitrogen and sulfur ligans in hydrogenation reactions

It has been found that homogeneous Pd complexes with sulfur ligands are by 50–500 times more resistant to thiophene action in hydrogenation reactions than homogeneous and heterogenized ones containing nitrogen ligands.

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50–500 .

     

Studies of H2S oxidation under catalytic conversion of Claus tall gases by response method

H₂S oxidation under catalytic conversion of Claus tail gases has been studied by the response method. The data obtained permit to suggest a reaction mechanism.

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H₂S . .