bluuebunny/crossref_metadata_2025_split huggingface dataset:
Practical expressions for the two‐center multipole expansion of r
Authors: Panas Itai 
Published: December 2004

AbstractAn explicit and transparent deduction of a conventional expression for the two‐center multipole expansion of the Coulomb potential, r, in terms of spherical harmonics, is perfomed. An intermediate expression in the deduction is shown to be well suited for transformation into a Cartesian representation. Practical formulas are produced that allow for safe and efficient implementations in computer programs. Electrostatic interactions between two pairs of point charges are computed and the importance to include the higher multipole interactions is stressed. © 1995 John Wiley & Sons, Inc.
Kinetics of atom–photon Interactions
Authors: Oláh K. , Bódiss J. 
Published: December 2004

AbstractIn order to avoid the violation of basic principles of macroscopic reversibility and detailed balance, we propose a cell kinetic model for atom‐photon interactions instead of Enstein's classical photon kinetic mechanism. Our model can be interpreted as a generalization of either mass action law or Einstein's original scheme. © 1995 John Wiley & Sons, Inc.
Isomeric interconversions in tamoxifen and related compounds: An AM1 study
Authors: Brewster Marcus E. , Huang Ming‐Ju , Pop Emil , Bodor Nicholas 
Published: December 2004

AbstractSemiempirical molecular orbital techniques (AM1) were applied to the study of cis–trans isomerism in tamoxifen and related compounds. AM1‐derived structures were in good agreement with X‐ray data. Theoretical evaluation indicated that both cis‐ and trans‐tamoxifen as well as the 4‐hydroxytamoxifen isomeric pair were very close in energy, confirming experimental results suggesting nearly equivalent populations of the two isomers under equilibrium conditions. Mechanistic studies included a determination of selected proton affinities to establish the nature and location of compound protonation as well as conformational studies of the formed carbocations. In particular, internal rotation about the incipient olefinic CC bond in the tamoxifen and 4‐hydroxytamoxifen carbocations provided a likely reaction mechanism. There evaluations suggested that the more rapid isomerization of 4‐hydroxytamoxifen as compared to tamoxifen was related to transition‐state stabilization through phenolic oxygen electron donation. © 1995 John Wiley & Sons, Inc.
Coupled‐Cluster approaches with an approximate account of triply and quadruply excited clusters: Implementation of the orthogonally spin‐adapted CCD + ST(CCD), CCSD + T(CCSD), and ACPQ + ST(ACPQ) formalisms
Authors: Piecuch Piotr , Toboła Robert , Paldus Josef 
Published: December 2004

AbstractThe orthogonally spin‐adapted (OSA) coupled‐pair (CCD) methods with an approximate account of triply and quadruply excited clusters are considered. We focus on the CCD + ST(CCD) perturbative estimate of the singly and triply excited clusters due to Raghavachari [J. Chem. Phys. 82, 4607 (1985)] and its ACPQ + ST(ACPQ) analog proposed by Paldus and Piecuch [Int. J. Quantum Chem. 42, 135 (1992)]. The latter approach combines the perturbative treatment of singles and triples with an approximate CCD theory corrected for connected quadruply excited clusters (ACPQ). We also consider the OSA version of the CCSD + T(CCSD) method (coupled‐cluster [CC] approach with singly and doubly excited clusters and noniterative perturbative account of triply excited clusters) introduced by Urban et al. {J. Chem. Phys. 83, 4041 (1985)}. The explicit OSA expressions for the previously neglected {P. Piecuch and J. Paldus, Theor. Chim. Acta 78, 65 (1990)} S(CCD) and S(ACPQ) terms are derived using diagrammatic methods of many‐body perturbation theory and graphical methods of spin algebras. The CCD + ST(CCD), CCSD + T(CCSD), and ACPQ + ST(ACPQ) formalisms have been implemented and the general purpose ab initio programs have been written using a newly developed procedure for improving the convergence of the reduced linear equation method {P. Piecuch and L. Adamowicz, J. Chem. Phys. 100, 5857 (1994)}. Results of the pilot calculations for few nondegenerate and quasi‐degenerate systems are presented and compared with the full configuration interaction data. © 1995 John Wiley & Sons, Inc.
A microscopic coupled‐cluster treatment of electronic correlations in Hubbard models
Authors: Bishop R. F. , Xian Y. , Zeng C. 
Published: December 2004

AbstractWe recently applied the coupled‐cluster method (CCM) with considerable success to several novel quantum spin‐lattice systems in the infinite bulk limit. In this article, we extend our CCM analysis to the electronic Hubbard models. In particular, based on a systematic approximation scheme within the CCM, we investigate the zero‐temperature properties of Hubbard models at half‐filling and with a single hole on a general bipartite lattice. Our aim was to provide the CCM framework for a systematic calculation of the properties of Hubbard models. © 1995 John Wiley & Sons, Inc.
Spin‐Adapted restricted Hartree–Fock reference coupled‐cluster theory for open‐shell systems: Noniterative triples for noncanonical orbitals
Authors: Neogrády Pavel , Urban Miroslav 
Published: December 2004

AbstractThe coupled clusters singles and doubles (CCSD) method for calculations of open‐shell systems with the single restricted Hartree–Fock (ROHF) reference determinant is extended by the noniterative triples to give CCSD(T). Our approach profits from the fact that (a) single‐ and double‐excitation amplitudes are spin‐adapted, which directly leads to a computationally less demanding algorithm than are nonadapted procedures and produces the spin‐adapted CCSD wave function and (b) triple excitations calculated from converged spin‐adapted (SA) CCSD amplitudes are also obtained more effectively. Altogether, computer demands of our SA CCSD(T) approach, applicable to high‐spin open‐shell cases which are well represented by a single‐determinant reference is comparable to that for closed‐shell systems. Our approach is not based on semicanonical orbitals, applied by Bartlett's group. However, we compare some other possible choices of ROHF orbitals to this “standard.” Numerical results for a series of atoms and molecules demonstrate little sensitivity to this selection. © 1995 John Wiley & Sons, Inc.
Ab initio conformational study of the CO ⃛H2 van der Waals dimer
Authors: Salazar Mary C. , De Castro Alexandra , Paz José L. , Diercksen Geerd H. F. , Hernández Antonio J. 
Published: December 2004

AbstractQuantum chemical fully ab initio conformational calculations were performed for the weakly bound van der Waals CO ⃛H2 dimer in the framework of the supermolecule approach. The counterpoise‐corrected interaction energies, computed through fourth‐order MBPT using the basis sets described recently by Sadlej, were in excellent agreement with results obtained with larger basis sets constructed to give accurate values for the electric moments and polarizabilities of CO and H2. The relative stability of the configurations studied here was collinear structures > parallel structure > T‐shaped structures. The collinear and parallel structures represent the most stable group of configurations. The present calculations show that they have values of De between 5.89 and 10.66 meV. The T‐shaped structures represent relatively less stable configurations with values of De between 0.84 and 2.92 meV. © 1995 John Wiley & Sons, Inc.
Application of the valence‐universal coupled‐cluster method based on various model spaces to 1S states of Be
Authors: Jankowski K. , Malinowski P. 
Published: December 2004

AbstractThe recently formulated atomically oriented valence‐universal theory (VU–CCSD/R) based on various complete model spaces is applied to the accurate description of the 2s2 1S, 2s3s 1S, 2p2 1S, and 3s2 1S states of Be. Two extensive 9s9p7d7f5g STO basis sets that differ by one s‐type function are employed. Both standard and nonstandard solutions of the VU–CC equations are considered. The eight values of the ground‐state energies obtained when considering various model spaces and basis sets were found to differ very little. The energies of the individual excited states disclosed a relatively weak dependence on the choice of model spaces defining the method (or, equivalently, on the fact whether they correspond to standard or nonstandard solutions). In turn, the energies of the excited states strongly depend on the STO basis set used in the calculations. To obtain a reliable description of both the ground state and excited states, well‐balanced STO basis sets have to be employed. © 1995 John Wiley & Sons, Inc.
Note on the variation step in the iteration–variation approach: Illustration on the hydrogen atom
Authors: Delhalle J. , Cizek J. 
Published: December 2004

AbstractAn analysis of the analytical properties of the first iterate of the iteration–variation approach applied to small Gaussian expansions is reported in the case of the hydrogen atom. The first iterates embody important qualitative improvements such as a cusp near the origin and better asymptotic decay at large values of r. Actual values of the properties depend on the quality of the initial functions in such a way that for very small Gaussian expansions the variation step is necessary. © 1995 John Wiley & Sons, Inc.
Spin‐unrestricted character of Kohn‐Sham orbitals for open‐shell systems
Authors: Pople John A. , Gill Peter M. W. , Handy Nicholas C. 
Published: December 2004

AbstractIt is argued that Kohn‐Sham calculations on open‐shell systems should be spin unrestricted in character. An application to the proton hyperfine constant in the methyl radical is presented. © 1995 John Wiley & Sons, Inc.
Nonlocal functionals for exchange and correlation in density functional theory: Application to atoms and to small atomic clusters
Authors: Alonso J. A. , Balbás L. C. , Rubio A. 
Published: December 2004

AbstractThe local density approximation (LDA) to exchange and correlation effects has well‐known limitations. The nonlocal weighted density approximation (WDA) corrects some of those defects. This is illustrated here by applications to free atoms and small atomic clusters. The WDA also induces a nonlocal kinetic energy functional that is tested for atoms. © 1995 John Wiley & Sons, Inc.
Frequency‐dependent linear response of superconducting systems
Authors: Lüders Martin , Gross E. K. U. 
Published: December 2004

AbstractWe present a density functional scheme for calculating the frequency‐dependent linear response of superconductors. The central result is a set of integral equations determining the linear response of the normal and anomalous densities to external perturbations. Analytic solutions of these integral equations are obtained for homogeneous systems with separable effective interactions. For inhomogeneous superconductors, the formalism leads to a scheme for calculating the critical temperature without explicitly solving the gap equation. © 1995 John Wiley & Sons, Inc.
Vibrational frequencies of sodium clusters
Authors: Aguilar J. G. , Mañanes A. , López M. J. , Iñiguez M. P. , Alonso J. A. 
Published: December 2004

AbstractThe vibrational frequencies of NaN clusters (2 ⩽ N ⩽ 72) are calculated by direct diagonalization of the dynamical matrix. Density functional theory with a spherically averaged pseudopotential is used to compute the total energy. The geometry is optimized by the simulated annealing technique. Contributions to the Hessian matrix due to electron relaxation following the ionic displacements are calculated in linear response theory. The frequencies are in the range 0‐220 cm−1 and the electron relaxation strongly modifies those of the modes dominated by radial oscillations, particularly the breathing mode frequencies that are proportional to N−1/3. The filling of atomic shells produces a stepwise behavior of the highest frequencies. The giant dipole resonance energies are obtained as a byproduct of the calculation. © 1995 John Wiley & Sons, Inc.
The Weizsäcker functional: Some rigorous results
Authors: Romera E. , Dehesa J. S. , Yañez R. J. 
Published: December 2004

AbstractThe Weizsäcker functional TW is a necessary element to explain basic physical and chemical phenomena of atomic and molecular systems in the general density functional theory initiated by Hohenberg and Kohn. Here, rigorous inequalities which involve the functional TW and two arbitrary power‐type density functionals ωα ≔ ∫ ρα(r)dr are found by the successive applications of Sobolev and Hölder inequalities. Particular cases of these inequalities give lower bounds to the Weizsacker functional of an N‐electron system in terms of a fundamental and/or experimentally measurable quantity such as, e.g., the Thomas–Fermi kinetic energy T0, the Dirac–Slater exchange energy K0 and the average electronic density 〈ρ〉 in doing so, some known relationships appear. A numerical Hartree–Fock study of the accuracy of some resulting lower bounds is carried out. Finally, rigorous relationships between the Weizsäcker functional and the Boltzmann–Shannon information entropy of the system under consideration are given. © 1995 John Wiley & Sons, Inc.
The quantitative analysis of surfaces by XPS: A review
Authors: Seah M. P. 
Published: December 2004

AbstractA general framework is presented for the quantitative analysis of surfaces by X‐ray photoelectron spectroscopy (XPS or ESCA). The approach starts by considering analysis using reference data recorded on the same instrument and under identical conditions as the analysed sample. Matrix factors are evaluated and the quantification for adsorbed layers and sputter profiles discussed. More popularly reference data are not recorded each time but are taken from the published literature. In this case the angular anisotropy term and analyser transmission functions need to be known. These are discussed and the analyser transfer functions of commercial spectrometers are presented in detail. Nine published reference data sets are assessed to test their correlation with the theoretical predictions. Theree sets are found to give moderate agreement but agree more closely with each other in their divergence from the theory for particular elements. This divergence enables a peak intensity factor to be defined which quantifies the intensity lost from a peak due to shake‐up events, etc. With this factor and the analyser transfer functions quantification can be made to an accuracy of 10% in all instruments from a single reference data set.
Limitations of ion etching for interface analysis
Authors: Holloway P. H. , Bhattacharya R. S. 
Published: December 2004

AbstractThe limitations of using ion sputtering for interfacial analysis are reviewed. It is concluded that many artifacts may degrade interfacial resolution—surface roughness, zone of mixing, bulk and surface diffusion, implantation, residual gas adsorption and matrix effects. Techniques to minimize these limitations are suggested. Some examples are: use of reactive ion beams, multiple ion beams, sample rotation and special mounting, varying the ion energy and incidence angle, and deconvolution. It is concluded, however, that sputtering may destroy atomic arrangement and chemical state information at the interface, and new approaches are needed to determine these interfacial parameters.
Surface analysis by glow discharge
Authors: Berneron R. , Charbonnier J. C. 
Published: December 2004

AbstractThis paper deals with the possibilities of glow discharge spectroscopy for surface analysis of metals. After a brief résumé of the principles and characteristics of the technique, examples of results obtained are given concerning the control of sub‐surface compositions after thermal or thermometric treatment of steels; surface analysis of low carbon steel strip at various stages of the production process; analysis of phosphate surface coatings; control of the surfaces of specimens for laboratory experiments; and laboratory studies of passivation phenomena.
X‐ray photoelectron spectroscopy studies of fired palladium electrode ink materials
Authors: Brown N. M. D. , Hewitt J. A. , Meenan B. J. 
Published: December 2004

AbstractThe oxidation state of palladium in an electrode ink dispersion, air‐dried on barium titanate dielectric substrates, has been studied using x‐ray photoelectron spectroscopy (XPS) as a function of both firing temperature and firing atmosphere. Several different states have been identified in amounts which vary over the firing temperature range of interest, i.e. palladium metal, a so‐called PdOads species, PdO and palladium in one or more higher oxidation states. No significant differences were observed for the two different contacting atmospheres used during firing, namely air and flowing nitrogen. Owing to overlap of the Pd 3p3/2 and the O 1s spectral envelopes, peak fitting of the oxygen signal was not attempted. Small amounts of residual carbonaceous ash were detected for all the samples studied over the whole range of firing temperatures employed.XPS analysis of a sample of the palladium ink, fired to 1350°C in air and subsequently etched using a fast atom bombardment (FAB) argon source, showed that the sub‐surface palladium was metallic in nature although the original metal surface was composed almost entirely of PdO. Thus, for these palladium inks, when fired to temperatures comparable with those used in multilayer ceramic capacitor (MLCC) manufacture, apart from a thin surface oxide layer the palladium present is in the metallic form, as required for electrode layer conduction.
Surface characterization of EVA copolymers and blends using XPS and ToF‐SIMS
Authors: Galuska A. A. 
Published: December 2004

AbstractThe surface chemistries of semi‐crystalline copolymers of ethylene (CH2CH2) and vinyl acetate (CH2CHCO2CH3) (EVAs) and blends of these copolymers with low‐density polyethylene (LDPE) have been examined critically for the first time using angle‐resolved XPS and time‐of‐flight SIMS (ToF‐SIMS) analyses. Specimens were fabricated using a variety of methods (commercial extrusion, spin coating and thermal compression) to determine the influence of processing conditions on EVA surface chemistry. The XPS and ToF‐SIMS analysis of these specimens has provided techniques for identifying surface EVA (also thermal oxidation), has provided both XPS and ToF‐SIMS methods for quantitative EVA analysis and has revealed the details of EVA surface chemistry. The XPS core‐level spectra indicate the presence of the ester (VA) and ether (surface oxidation) species, but do not provide positive EVA identification. The ToF‐SIMS spectra show features specific to both the ethylene and vinyl acetate portions of the polymer. Both XPS and ToF‐SIMS analyses have been calibrated to provide quantitative VA (error < 2 wt.% VA) and oxygen (error < 1.0 at.% oxygen) analyses. Surface VA content was found to increase linearly with bulk VA content, and was not influenced by the type of fabrication method used. The EVA surfaces appear to consist of two layers. The near‐surface region (> 20 Å depth) is dominated by a VA‐poor (ethylene‐rich) layer. This region is covered by a thin (⩽20 Å thick) VA‐enriched layer.
Spectroscopic characterization of stainless‐steel surfaces treated by plasma
Authors: Deshayes L. , Charbonnier M. , Prakash N. S. , Gaillard F. , Romand M. 
Published: December 2004

AbstractStainless‐steel substrates were surface treated then coated with thin amorphous hydrogenated carbon films that were deposited by CH4 plasma polymerization. The effects of these surface treatments were studied by x‐ray photoelectron spectrometry, ion scattering spectrometry and Fourier transform infrared spectrometry. A few minutes of O2 plasma treatment at a power density of 0.5 W cm−2 was shown to modify strongly the surface composition of these substrates, with chromium present at the surface being transformed gradually, from Cr2O3 to CrO3, before disappearing altogether. In contrast, NH3 plasma of similar power, but generated over a few seconds, cleaned and functionalized the surface. Both of these treatments proved to be highly efficient in promoting good carbon film adhesion to the substrate.
Effects of compounding and extrusion variables on degree of fusion and impact strength of PVC window profile
Authors: Batiste J. , Choi P. , Lynch M. , Rudin A. , De Carvalho L. H. 
Published: December 2004

AbstractThe effects of temperature in twin screw extrusion of a window profile compound have been studied. Compounds were made with and without an acrylic impact modifier. Fusion levels of the extruded profiles were rated from values of the rubbery plateau modulus at temperatures near 110°C. Impact strength was measured at room temperature using notched tensile specimens at 1 m/s jaw separation rate. The impact strength of these materials does not increase with fusion level once an adequate degree of gelation has been achieved. The impact‐modified compound shows a dramatic improvement in impact strength when the melt temperature was increased from 319°F to 343°F. A further increase to 365°F had no effect. The compound without impact modifier exhibited no improvements in impact strength over the whole extrusion temperature range. Conflicting reports in the literature on effects of fusion level on impact strength of PVC articles probably reflect different interactions between extrusion conditions and compound composition.
Über Komplexverbindungen. VII. Lichtabsorption von Mono‐ und Diacido‐amminen des dreiwertigen Kobalts mit Fettsäureresten
Authors: Linhard Martin , Weigel Melitta 
Published: December 2004

AbstractDie Lichtabsorption von 38 Kobalt(III)amminkomplexen mit einem bzw. zwei in cis‐ oder trans‐Stellung koordinativ gebundenen Fettsäureresten wird im Gebiet von 15000 bis 45000 cm−1 gemessen und diskutiert.Die Spektren bestehen im allgemeinen aus zwei niederen Banden I und II (log ϵ ∼ 2) im Sichtbaren und nahen U. V. und einer hohen Bande III (log ϵ ∼ 4) im entfernteren U. V.Die Banden I und II gehören zu Elektronenübergängen in der Edelgaszwischenschale. Innerhalb der homologen Reihen der drei Salztypen weisen nur die Salze der stärkeren Säuren Abweichungen auf, die zwar deutlich und systematisch, aber gering sind. Allgemein liegen die Banden I und II gegenüber jenen der entsprechenden Luteosalze bei kleineren Wellenzahlen und zwar zunehmend in der Reihenfolge: Luteo → Acido → cis‐Diacido → trans‐Diacido‐komplexe. Die Bande I der trans‐Diacido‐komplexe spaltet hierbei deutlich in zwei Teilbanden auf. Für die übrigen niederen Banden wird eine (geringere) Aufspaltung der Bande I als wahrscheinlich, der Bande II als möglich befunden. Die Aufspaltung wird in Analogie zu Normalkomplexen als Folge der größeren oder kleineren Asymmetrie der Kraftwirkungen der Liganden gedeutet.Aus der Bandenverschiebung und ‐aufspaltung ergibt sich eine brauchbare Regel für die Zuordnung von Diacido‐salzen zur ces‐ bzw. trans‐Reihe.Die hohe U. V.‐Bande III ist dem Chromophor der Carboxylgruppe zuzuordnen, dessen Absorption durch die Komplexbindung stark nach kleineren Wellenzahlen verschoben ist, und zwar auf Grund ihrer gleichen Lage in Ammin‐ und Aethylendiaminkomplexen, ihrer starken Abhängigkeit von der Art der Fettsäureliganden, ihrer Beziehungen zu den Banden der freien Fettsäuren und zu den Bildungswärmen analoger stereoisomerer Salze.Die viel weiter im U. V. zu erwartenden Amminbanden tauchen vollständig unter den Carboxylbanden unter.