bluuebunny/crossref_metadata_2025_split huggingface dataset:
Brillouin zone double integrals
Authors: Oriade J. O. O. 
Published: December 2004

AbstractA semianalytic scheme is proposed for the evaluation of Brillouin zone (BZ) double integrals such as are met in the evaluation of Compton profiles (CPS) and the angular distribution of annihilation photons (ADAPS) obtained in single‐slit positron annihilation experiments. The difficulty that arises due to the jump discontinuities in the momentum density at the generalized Fermi surfaces (FS +HMC), pF = kF + g, where kF is the electron Fermi momentum vector and g is a reciprocal lattice vector, is addressed.
Perturbation calculation on the hydrogen atom in electric and magnetic fields
Authors: Fernández Francisco M. , Castro Eduardo A. 
Published: December 2004

AbstractA generalization of a perturbation theory without wave function is developed which applies to a hydrogen atom perturbed by magnetic and electric fields. A double perturbation expansion for the Stark–Zeeman effect for parallel fields is considered and results for the states obeying |m| = l = n − 1 in the zero field limit are presented. Other problems that can be treated this way are discussed.
A method for the calculation of transition moments between electronic states of molecules using a different one‐electron basis set for each state
Authors: Theodorakopoulos G. , Petsalakis I. D. , Nicolaides C. A. 
Published: December 2004

AbstractA state‐specific approach to the calculation of transition moments between molecular electronic states requires that the wavefunction for each state is expanded in its optimum one‐electron basis and that nonorthonormal basis techniques are used for the calculation of the transition moment integrals. A method has been developed for carrying out such nonorthonormal basis calculations, based on the corresponding orbitals transformation and appropriately defined density matrices, which may be used with configuration interaction (CI) wavefunctions. Further improvements of the method have resulted in a decrease in the time required for the calculations and thus allow its application with moderately large CI expansions for each state. Nonorthonormal basis calculations on transition moments in H2O have been carried out using the above method. The results are in agreement with those of large MRD‐CI calculations.
Iteration of the Schrödinger equation starting from Hartree–Fock wave functions
Authors: Avery John , Antonsen Frank 
Published: December 2004

AbstractMethods are discussed for iterating the many‐particle Schrödinger equation starting from Hartree–Fock wave functions. It is shown that when the Hartree–Fock wave function is expressed as a linear combination of the appropriate basis functions in hyperspherical coordinates the hyperangular integrals needed for iteration can be evaluated analytically. It is also shown that the first‐iterated solutions contain terms corresponding to angular correlation.
A semiempirical investigation of interelectronic exchange coupling in bisected poly(1,4‐phenylene) polycation model systems
Authors: Lahti Paul M. 
Published: December 2004

AbstractAM1 SCF‐MO‐CI computations find the bisected biphenyl dication to have nearly degenerate triplet and singlet states, with the lowest‐energy state being a quininoid singlet planar dication. The bisected perchlorobiphenyl dication favors a triplet ground state by a small amount (0.4‐1.9 kcal/mol), in qualitative agreement with recent experimental findings and with theoretical expectations that such an orthogonal open‐shell pi‐system should exhibit ferromagnetic exchange coupling. The higher oligomeric bisected para‐linked phenylenes polycations do not show an appreciable computational preference for a high‐spin multiplicity ground state either with or without perchlorine substitution. Chlorine substitution para to the 1,1′‐linkage may lend a unique stabilization to the biphenyl system, which is not available in higher oligomeric analogs of poly(1,4‐phenylene)s. The small magnitude of ferromagnetic exchange in these systems suggests that small geometric or substituent effects may confound experimental efforts to design polymeric ferromagnetic materials by this strategy. © 1992 John Wiley & Sons, Inc.
Intermediates of the borane reduction of some imidazolidines: An AM1 study
Authors: Bodor Nicholas , Prokai Laszlo 
Published: December 2004

AbstractAmine(NB)‐aminoborane internal complexes and 1,3,2‐diazaborolidines were recently identified as intermediates of the borane reduction of imidazolidino[1,2‐d]dithiazepines. Theoretical Mo calculations were used to obtain the structural, conformational, and electronic properties and heats of formation of the boron compounds in the framework of the semiempirical AM1 approximation. Internal constraints in the bicyclic system were analyzed through comparisons with the calculated molecular geometries, electron distribution of monocyclic, and open‐chain models. The geometry of the five‐membered diazaborolidine systems becomes distorted upon building up the complex bicyclic structure, compared to the nearly planar monocycles. The weak coordinative nitrogen–boron bond (calculated bond order around 0.5) in the internal complexes exerts less conformational strains in the adjoining nine‐membered ring containing the disulfide than does the covalent NB bond in the corresponding 1,2,3‐diazaborolidine. Thus, the internal constraints of the bicyclic system is taken up by the five‐membered ring to a lesser degree in the 1,3,2diazaborolidine than in the internal complex. © 1992 John Wiley & Sons, Inc.
X–NO2 rotational energy barriers: Local density functional calculations
Authors: Habibollahzadeh Dariush , Murray Jane S. , Grice M. Edward , Politzer Peter 
Published: December 2004

AbstractThe X–NO2 rotational energy barriers of nitromethane, nitroethylene, nitrobenzene, and a group of nitramines have been computed using a local density functional (LDF) procedure, using ab initio Hartree–Fock (HF)‐optimized structures of the ground and rotational transition states. The results have been discussed in relation to HF and some correlated ab initio values and the available experimental data. Our LDF barriers are overall quite reasonable, in generally satisfactory agreement with the experimental and correlated ab initio results. © 1993 John Wiley & Sons, Inc.
Studies on the structural unit and suspending terminal groups in the quasi‐one‐dimensional periodic system
Authors: Zhu Jin , Yan Ji‐Min , Yan Da‐Yu 
Published: December 2004

AbstractQuasi‐one‐dimensional periodic systems were investigated by the new proposed extrapolation method. The effect of the selection of the different structural units and their spin states on the periodic system was also studied. A quantum chemical calculation investigation of a 28 quasi‐one‐dimensional periodic system with MNDO (UHF) and EHMO/ASED–EHCO/ASED was undertaken. Quantum chemical calculation results with the MNDO (UHF) method showed that the proposed new method could be applied in the situation of the more precise semiempirical method. The selection of the different structural units and their spin states do not affect the extrapolated structural unit energy. The energy of suspending terminal group is generally higher for those with a higher bond order. The interaction energy between the suspending terminal groups generally decreases with the chain length. Comparison between the extrapolation results of EHMO/ASED and those from the crystal orbital calculation of EHCO/ASED indicates their equivalence, thus confirming the validity of the proposed method. © 1995 John Wiley & Sons, Inc.
A rapid generalized valence‐bond algorithm for semiempirical NDDO calculations
Authors: Cullen John M. 
Published: December 2004

AbstractA recently developed algorithm based on the coupled cluster ansatz for the generalized valence‐bond perfect‐pairing model is adapted for the NDDO class of semiempirical methods. It allows for the calculation of the nondynamic electron correlation and executes as rapidly as the semiempirical molecular orbital method. To assess the interplay of the nondynamic and dynamic electron correlation vs. parameterization, preliminary results are presented for rotation about a double bond, dissociations about single bonds, and the relative stabilities of biradical isomers. © 1995 John Wiley & Sons, Inc.
Low energy positrons from metal surfaces
Authors: Dale J. M. , Hulett L. D. , Pendyala S. 
Published: December 2004

AbstractThere is reason to believe that slow positron spectroscopy will have value for surface analyses, but in order to develop practical methods it is necessary to devise monoenergetic sources of positrons that output usable intensities. This paper describes how this can be achieved by preparing certain metal surfaces to act as moderators for fast positrons from radioactive sources. After entering the moderator, the positrons are thermalized and a certain fraction are re‐emitted back into the vacuum. They can then be extracted by an electrostatic field and accelerated to any desired energy. Yields of low energy positrons were found to be generally large for certain metals having negative positron work functions (theoretically calculated). It is also necessary to minimize bulk defects, which act as positron traps. Tungsten and molybdenum are metals having negative work functions which can be easily prepared as effective moderators by simply heating in vacuum. This effects a cleaning by volatilizing oxides and anneals defects. The inertness of their surfaces towards oxidation allows them to maintain the negative work function effect which might otherwise be reduced by exposure to air and poor vacuum. These results have been utilized by the authors to design a monoenergetic positron gun to measure discrete energy losses in reflection spectra and threshold absorption effects. A Brandeis University group has used a tungsten moderator gun to make the first experimental measurements of low energy positron diffraction spectra.
Identification and quantification of Cu contamination on GaAs surfaces
Authors: Sykes D. E. , Chew A. , Hall D. D. , Crapper P. A. , Grant I. R. , Lamb M. S. M. , Lunn M. , Brozel M. R. , Davies P. 
Published: December 2004

AbstractSecondary ion mass spectrometry has been used to identify the presence of Cu contamination on undoped semiinsulating GaAs wafer surfaces following polishing under certain conditions. The presence of a contaminating species on the wafer surface is indicated by the influence of pre‐etch treatments on electrical measurements performed on heat‐treated wafers, with and without Si implants. The identification of Cu as a contaminant is confirmed by photoluminescence measurements. With the appropriate wafer preparation process, the level of Cu contamination is below the SIMS detection limit of <1 × 1016 atoms cm−3.In the SIMS analysis of the surface‐contaminated wafers, the Cu depth profile shape was dependent on the primary beam bombardment energy, suggesting a chemical segregation of Cu out of the altered layer, a redistribution that is known to occur in Si.To quantify the surface concentration of Cu, GaAs wafers were deliberately contaminated with Cu, heat treated and analysed with glow discharge mass spectrometry and SIMS to provide a cross‐calibration.
Characterizing dryblending behavior of PVC resins
Authors: Changfoot J. 
Published: December 2004

AbstractAn important characteristic of a resin is the speed with which the polymer can be processed with the plasticizer in the plant, or its dryblending characteristics. The dryblending behavior of the polymer is dependent upon its microstructure and macrostructure. It is well known that some degree of porosity is required in order to obtain good dryblending properties; however, there are also other factors which affect the dryblending. Another factor, which is defined as the Swelling Index, is identified, and the use of this to help characterize dryblending behavior of different resins is discussed.
Zur Kenntnis der Kieselsäuren. VIII. Über Organisch substituierte Siliciumamide und deren Derivate
Authors: Schwarz Robert , Weigel Fritz 
Published: December 2004

AbstractUmsetzung von Organochlorsilanen mit Ammoniak führt zu entsprechenden Organosiliciumamiden, die weiter zu Disilazanen kondensiert werden. Hierbei entstehen aus Diamiden auch Cyclosilazane. Bei Umsetzung mit Hexamethylendiamin wurde ein Triphenoxy‐Cyclohexylsilazin, bei Reaktion von Trialkylsiliciumamid mit Adipinsäurechlorid ein Triisopropoxy‐cyclotetramethylendiketosilazin dargestellt. Reaktionen rein organischer und siliciumorganischer Verbindungen gleichen Typs werden verglichen, der Unterschied wird diskutiert.
Über einige Verbindungen des Samariums vom NaCl‐Typ
Authors: Iandelli A. 
Published: December 2004

AbstractFolgende Verbindungen sind hergestellt und röntgenographisch untersucht worden: SmN, SmP, SmAs, SmSb, SmBi, SmS, SmSe, SmTe und NdBi. Sie besitzen alle NaCl‐Struktur mit den Gitterkonstanten: 5,039 (SmN); 5,760 (SmP); 5,921 (SmAs); 6,271 (SmSb); 6,362 (SmBi); 5,970 (SmS); 6,200 (SmSe); 6,594 (SmTe); 6,424 Å (NdBi); alle ± 0,003 Å.Der Verlauf der a0−Werte aller bekannten MX‐Verbindungen des La, Ce, Pr, Nd, Sm, Eu mit dem gleichen Nichtmetall kann mit einem Radienwertesystem für die einzelnen Elemente erklärt werden. Die Metallradien entsprechen denjenigen trivalenter Ionen, mit Ausnahme von SmS, SmSe, SmTe, EuS, EuSe, EuTe und CeN. Die genannten Sm‐ und Eu‐Verbindungen dürften Sm2+‐ bzw. Eu2+‐Ionen enthalten, in CeN dürfte ein gewisser Anteil von Ce4+‐Ionen vorhanden sein.
Über antimonorganische Verbindungen
Authors: Kolditz Lothar , Gitter Michael , Rösel Ekkehard 
Published: December 2004

AbstractEs wird gezeigt, daß antimonorganische Verbindungen des Typs R3SbCl2, R3SbClOCH3 und R2SbCl3 (wobei R = CH3‐, C6H5‐, C6H5CH2‐) keine Neigung zur Aufspaltung in heteropolare Verbindungen besitzen. In polaren Lösungsmitteln haben sie keine elektrolytische Leitfähigkeit, in unpolaren Lösungsmitteln wird keine Aggregation festgestellt. Diese Verbindungen verhalten sich damit anders als Antimon(V)‐halogenide und Antimon(V)‐alkoxyhalogenide, die in unpolaren Lösungsmitteln aggregieren und in polaren Lösungsmitteln Ionen bilden. Verbindungen des Typs R3SbClOH und R2SbCl2OH wurden in fester Form nicht erhalten, Es entstehen die dimeren Verbindungen R3SbClOSbClR3 bzw. R2SbCl2OSbCl2R2 (R = C6H5‐, C6H5CH2‐).
Präparative und spektroskopische Untersuchungen an Tetrametaphosphimsäure und ihren Derivaten. III. Tetrametaphosphimsäure, ihr Hydrat und die Deuteriumverbindungen
Authors: Steger E. , Lunkwitz K. 
Published: December 2004

AbstractDie Entwässerung von Tetrametaphosphimsäure‐Dihydrat wird in Beziehung zur Teilchengröße studiert. Deuteriumsubstitution erfolgt durch Austausch mit D2O. Die infrarotspektroskopische Untersuchung der verschiedenen Produkte erlaubt eine exakte Zuordnung der Frequenzen. Starke Wasserstoffbrücken vom Potentialverlauf mit 2 Minima sind zu bemerken. Die PO‐Bindungen sind schwächer als in den PO2‐Gruppen der Metaphosphate. Es besteht kein Grund, Hydroniumionen im Tetrametaphosphimsäure‐Dihydrat anzunehmen.
Die Dichte wäßriger Cd(NO3)2‐Lösungen bei 25°C
Authors: Fischer L. 
Published: December 2004

AbstractEs werden die Ergebnisse von Dichtemessungen an wäßrigen Cd(NO3)2‐Lösungen bei 25°C im Konzentrationsbereich von etwa 0,005 bis 0,1 mol. 1−1 mitgeteilt und die daraus berechneten scheinbaren Molvolumina kurz diskutiert.
Zur Kenntnis des dreiwertigen Mangans: Verbindungen des Mangan(III)‐chlorids mit Aminen und einigen Äthern
Authors: Funk H. , Kreis H. 
Published: December 2004

AbstractMangan(III)‐chlorid liefert mit Aminen hauptsächlich 1:3‐Addukte, die feuchtigkeits‐empfindlich, aber bei Raumtemperatur beständig sind. Mit α,α′‐Dipyridyl und o,o′‐Phenanthrolin entstehen wasserlösliche Komplexe, in denen die Chloratome durch andere Anionen ersetzbar sind. — Die Äther‐Addukte sind temperaturempfindlich.Die Umsetzung von Mangan(III)‐chlorid mit Acetylaceton führt zur Substitution von einem bzw. zwei Chloratomen durch das Diketon.
Die Kristallstruktur von Lithiummetaperiodat, LiIO4
Authors: Kraft Thorsten , Jansen Martin 
Published: December 2004

AbstractErstmals wurden Einkristalle von LiIO4 erhalten. Nach der Röntgenstrukturanalyse (monoklin, P21/n; a = 525,5(3), b = 851,1(4), c = 796,9(5) pm, β = 104,21(3)°; Z = 4; 2 148 unabhängige Reflexe, R = 0,024) wird Iod tetraedrisch und Lithium stark verzerrt trigonal‐bipyramidal von Sauerstoff koordiniert. Dabei sind jeweils zwei Lithium‐Sauerstoff‐Polyeder miteinander kantenverknüpft. Es besteht Isotypie zu LiAlH4. Die Struktur wird diskutiert und mit denen anderer Metaperiodate und Tetrahydridoaluminate verglichen.
Kristallstrukturbestimmungen an vier monoklinen Weberiten Na2MIIMIIIF7 (MII = Fe, Co; MIII = V, Cr)
Authors: Peschel B. , Molinier M. , Babel D. 
Published: December 2004

AbstractDurch Festkörperreaktion der binären Fluoride wurden Einkristalle der folgenden Weberite dargestellt und röntgenographisch deren monokline Struktur bestimmt (Raumgruppe C2/c, Z = 16): Na2FeVF7 (a = 1 271,0(3), b = 742,9(1), c = 2 471,6(5) pm, β = 100,03(3)°; R1 = 0,043 (1 545 Reflexe); FeF = 203,8, VF = 193,0 pm); Na2FeCrF7 (a = 1 262,5(3), b = 739,1(1), c = 2 460,5(5) pm, β = 99,93(3)°; R1 = 0,029 (2 340); FeF = 203,6, CrF = 190,5 pm); Na2CoVF7 (a = 1 270,3(5), b = 739,1(3), c = 2 465,1(10) pm, β = 100,02(3)°; R1 = 0,028 (2 250); CoF = 201,6, VF = 193,6 pm); Na2CoCrF7 (a = 1 257,8(3), b = 733,5(1), c = 2 441,5(5) pm, β = 99,64(3)°; R1 = 0,030 (2 227); CoF = 201,2, CrF = 190,2 pm). Zu den genannten mittleren Abständen in den verzerrten [MF6]‐Oktaedern und zur Form der [NaF8]‐Koordination werden Einzelheiten mitgeteilt und diskutiert.
K3MnH5, das erste salzartige Manganhydrid
Authors: Bronger W. , Hasenberg S. , Auffermann G. 
Published: December 2004

AbstractDie Synthese von K3MnH5 bzw. K3MnD5 gelingt durch Umsetzung von Kaliumhydrid (‐deuterid) mit Manganpulver bei einem Wasserstoffreaktionsdruck > 3000 bar und einer Temperatur von 875 K. Röntgenographische Untersuchungen an pulverförmigen Proben und elastische Neutronenbeugungsexperimente an der deuterierten Verbindung mit Hilfe des Flugzeitspektrometers LAD in Abhängigkeit von der Temperatur (5–600 K) führten zur vollständigen Strukturaufklärung.Die Atomanordnung enthält neben isolierten [MnH4]2−‐Tetraedern Hydridionen, die ausschließlich von Kaliumionen koordiniert sind. Der Strukturaufbau entspricht dem im Cs3[CoCl4]Cl (Raumgruppe: 14/mcm, Z = 4). Die Temperaturabhängigkeit der magnetischen Suszeptibilitäten zeigt oberhalb von 50 K Curie‐Weiss‐Verhalten. Unterhalb 50 K treten offensichtlich antiferromagnetische Kopplungen auf.
Thia‐ und Selena‐arachno‐undecaboran 6,7‐μ‐(CH3E)B10H13 Kristallstruktur von arachno‐6,7‐μ‐(CH3Se)B10H13 Theoretische Untersuchungen der Molekülstrukturen und 11B‐NMR‐Verschiebungen von arachno‐6,7‐μ‐(CH3E)B10H13
Authors: Binder H. , Söylemez S. , Stöckle R. , Pfitzner A. , Hofmann M. , Schleyer P. v. R. 
Published: December 2004

AbstractBei der Reaktion zwischen B10H14 und (CH3)2S erfolgt unter H2‐Abspaltung eine zweifache Adduktbildung, die zu 6,9‐[(CH3)2S]2B10H12 führt. Die analoge Umsetzung zwischen B10H14 mit Disulfanen bzw. Diselenanen führte jedoch nicht zu den 6,9‐Dichalkogen‐verbrückten Derivaten. Bei der Umsetzung mit (CH3)2S2 findet selbst unter Refluxbedingungen keine Reaktion statt, wohl aber mit dem Trisulfan (CH3)2S3. Die Reaktion verläuft aber nicht unter H2‐Abspaltung. Vielmehr wird dabei ein Brücken‐H‐Atom durch eine CH3S‐Gruppe substituiert unter Bildung von (CH3S)B10H13 2. Im Gegensatz zu (CH3)2S2 findet aber mit (CH3)2Se2 ebenfalls eine Brücken‐H‐Substitution statt, wobei (CH3Se)B10H13 3 gebildet wird. 2 und 3 konnten in reiner Form isoliert und 11B‐NMR‐spektroskopisch charakterisiert werden. Von 3 wurde eine Röntgenstrukturanalyse durchgeführt (Raumgruppe P21/c) und von 2 und 3 die Molekülstrukturen auf MP2‐Niveau optimiert sowie 11B‐NMR‐ Verschiebungen mit IGLO‐SCF, GIAO‐SCF und GIAO‐B3LYP berechnet.
Synthese und Struktur eines zweikernigen Gadolinium(III)‐Komplexes: Magnetische Austauschwechselwirkungen in alkoxyverbrückten Komplexen der Lanthanoiden
Authors: Plass Winfried , Fries Guido 
Published: December 2004

Synthesis and Structure of a Binuclear Gadolinium(III) Complex: Magnetic Exchange Interactions in Alkoxy Bridged Lanthanide ComplexesThe Schiff Base ligand N‐salicylidene‐2‐(bis‐(2‐hydroxyethyl)amino)ethylamine (H3sabhea) reacts with Gd(NO3)3 · 6 H2O in methanol solution to yield the alkoxy bridged binuclear gadolinium(III) complex [{Gd(Hsabhea)(NO3)}2] · 2MeOH (1). 1 crystallizes in the monoclinic space group P21/c with a = 1014.8(2), b = 2059.2(4), c = 867.5(2) pm, β = 106.72(2)°, and Z = 2. The two gadolinium atoms are bridged by two alkoxide oxygen atoms with angles of 107.60(11)° at the oxygen bridgeheads and a GdGd separation of 376.43(7) pm. A variable‐temperature magnetic susceptibility study (2 to 280 K) of 1 revealed an antiferromagnetic coupling between the Gd(III) ions with J = −0.198 cm−1 (g = 1.975).
Beliefs about appropriate pain behavior: cross‐cultural and sex differences between Japanese and Euro‐Americans
Authors: Hobara Mieko 
Published: December 2004

AbstractThe Appropriate Pain Behavior Questionnaire (APBQ) was employed to examine the effects of the participants' sex and culture on their beliefs regarding gender‐appropriate pain behavior. The APBQ examines beliefs about the social acceptability to male and female participants of the behavioral and verbal expressions of pain by men and women (referents) in the presence of others [Nayak, S., 2000. Cross Cult Research 34, 135–151]. The participants were 18 male and 14 female Japanese, and 11 male and 21 female Euro‐Americans. There was a significant effect of sex: female participants considered pain behaviors more acceptable than male participants. There was a significant effect of culture: compared to both male and female Japanese, Euro‐American participants rated pain behaviors in both sexes to be more acceptable. There was also a significant effect of referent gender: for both sexes in both cultures, pain behaviors in women were rated as more acceptable than in men. Furthermore, a significant interaction was found between referent gender and sex of the participant: Male and female participants of both cultures were equally accepting of pain behaviors in women, but male participants were less accepting of pain behaviors in men than in women. There also was a significant interaction between referent gender and culture of the participant: Japanese participants considered pain behavior in both genders to be less acceptable than did Americans. The results are explained in terms of cultural traditions and social roles, and have clear implications for clinical treatment and diagnosis.