bluuebunny/crossref_metadata_2025_split huggingface dataset:
Population analysis of pair densities: A link between quantum chemical and classical picture of chemical structure
Authors: Ponec Robert , Strnad Martin 
Published: January 2005

AbstractThe pairon population analysis based on the geminal expansion of pair densities is introduced and applied. As demonstrated by numerical data calculated for a series of simple molecules by the semiempirical MNDO method, the resulting populations provide a new simple means of visualizing the molecular structure. In addition to the reproduction of classical structural formula including the multiplicity of individual bonds, the resulting populations confirm the transferability of bond energies and also provide a simple interpretation of the concept of quantum chemical valence. © 1994 John Wiley & Sons, Inc.
Accurate computation of eigenfunctions for screened coulomb potentials
Authors: Núñez Marco A. 
Published: January 2005

AbstractA numerical method is developed to obtain a sequence of functions converging to the eigenfunctions of the Schrödinger operator H = − ½ Δ + V(r) for V(r) = − Z/r + χ(r), where χ(r) is a continuous and bounded‐from‐below function for (r ∈ 0, ∞). The criterion of convergence in the convergence in the norm of the Hilbert space L2(0, ∞), which assures the accurate computation of the expected values for a symmetric operator, as we show. The method consists of solving the dirichlet problem inside a box of radius n by the Ritz method, whose convergence in the norm is proved using the compactness criterion. Using a physical argument, we show that the bounded states of the Dirichlet problem converge to those the unbounded system in the norm of L2(0, ∞) as n grows. The method is applied to the potentials V(r) = − Z/r + ari (i ≥ 0) and V(r) = − Z/r + a/(1 + rλ); in each case, we show the numerical convergence of eigenfunctions, energies, and density moments. © 1994 John Wiley & Sons, Inc.
Improved local density functional approach for atomic systems
Authors: Ghosh Swapan K. , Deb B. M. 
Published: January 2005

AbstractThrough a new local density approximation to the kinetic energy density functional introduced by us recently, a simple Thomas–Fermi‐like scheme for the direct calculation of electron density in atoms is proposed. The calculated density is nonsingular at the nucleus and the energy values are in very good agreement with the corresponding Hartree–Fock results for atoms. © 1994 John Wiley & Sons, Inc.
Calculating excitation energies with the help of cumulants
Authors: Schork Tom , Fulde Peter 
Published: January 2005

AbstractRecently, it has been shown that the ground‐state energy of a quantum many‐body system can be written in terms of cumulants. In this article, we show that the energies of excited states can be expressed similarly. These representations are suitable for various approximation schemes, e.g., projection techniques. The explicit use of cumulants ensures size consistency in all approximations. The theory is then applied to the computation of the energy bands of a semiconductor with a diamond structure. As we focus especially on the effects of electron correlations, we consider a simplified model and rederive results obtained previously by the variational local ansatz method. © 1994 John Wiley & Sons, Inc.
The band gap of alternant 1D π‐electron systems
Authors: Tyutyulkov N. , Dietz F. , Klein D. J. , Seitz W. A. , Schmalz T. G. 
Published: January 2005

AbstractWithin the framework of the AMO–EHF approximation for the Hubbard model, it is shown that the band gap ΔE of an arbitrary regular alternant 1D π‐system (polymer), having a singlet ground state, is different from zero, i.e., the ground state is a dielectric one. At least one of the three components of the energy gap—the topological, Δtop; the geometrical, Δgeom; or the correlation, Δcorr (combined via the equation ΔE = {Δ + (Δtop + Δgeom))2}1/2—is different from zero. Numerical results for several 1D alternant polymers with conjugated π‐systems are given. © 1994 John Wiley & Sons, Inc.
Linear response calculation of potential energy curves of BH
Authors: Jaszuński Michał 
Published: January 2005

AbstractThe multiconfiguration time‐dependent Hartree–Fock (MC TDHF) approximation is applied to study the excited states of the BH molecule. The potential energy curves and spectroscopic properties of the excited states are analyzed. The MC TDHF results are compared to similar MC SCF calculations for individual excited states. © 1994 John Wiley & Sons, Inc.
Electrostatic potential and electric field mapping of some sweeteners of the suosan series: A search for the structure–activity relationship
Authors: Santhosh C. , Mishra P. C. 
Published: January 2005

AbstractElectrostatic potential and electric field maps of some suosan series of sweeteners have been studied. Geometries optimized using the MNDO molecular orbital method and charge distributions obtained by the Mulliken population analysis were employed in the calculations. Sweetness potencies of the molecules were compared with electrostatic potentials and electric field strengths near the terminal COOH group. The observed sweetness potencies of the compounds and calculated electric fields near the carbonyl oxygen of the COOH group are found to be strongly correlated. © 1994 John Wiley & Sons, Inc.
Some remarks concerning spherulitic growth
Authors: Gadomski A. , Łuczka J. 
Published: January 2005

AbstractA new approach to the description of the formation of spherulites in a polymer solution is proposed. It is based on an analytical scheme that takes into account the mass conservation law as a fundamental evolution equation. Three physically interesting cases are considered, both which, on deterministic and stochastic levels, can reflect an asymptotic behavior characteristic for spherulites, namely, R(t) ∝︁ t, where R(t) is a radius of the spherulite measured at instant t. A few examples of systems similar to that under study are mentioned. © 1994 John Wiley & Sons, Inc.
Calculations of the electronic structure of various aperiodic polymers by an elongation method
Authors: Imamura Akira , Aoki Yuriko , Nishimoto Kazushi , Kurihara Youji , Nagao Atsuhiro 
Published: January 2005

AbstractAn elongation method, which had already been proposed to calculate the electronic structure of aperiodic polymer efficiently, was applied to atactic polypropylene, with the approximation level of the extended Hückel method. The atomic populations thus calculated were found to be dependent sensitively on the tacticity of the polymer. Next, this elongation method was applied to the π‐electron stacking system composed of ethylene and butadiene, etc. Excellent agreement was found between the elongation method and the usual extended Hückel calculations. Thus, the elongation method can confidently be applied to π‐electron molecular crystal systems. Finally, the local density of states of polyacetylene with both cis–transoid and trans–cisoid structures was calculated. We found that the site with large local density of state in the valence band of a polymer chain gives large electron transfer to the site with large local density of state in the conduction band of another polymer chain. © 1994 John Wiley & Sons, Inc.
Effective crystal field approach to the binding energy calculation of alkaline metals
Authors: Koleżzyńnski A. , Ptak W. S. , Tkacz‐śmiech Katarzyna 
Published: January 2005

AbstractA method of description of a crystalline solid is presented and discussed in the light of the variational method. The proposed method refers to the muffin‐tin cellular method but it is formulated in the language of electron density, without referring to wave‐function treatment. Model calculations of p‐dependent binding energy for alkaline metals have been performed. The results show that the proper adjustment of the effective charge of atomic core zeff parametrizing the electron density in the cell allows one to reproduce exact values of binding energy at the equilibrium distance. The numerical results prove that the dependence between the charge zeff and the radius of the cell RMT may be represented by the functión zeff = (21)1/2(1 + B exp(‐ARMT)), where A and B are numerical parameters changing with high regularity throughout the period and I denotes the first ionization energy. © 1994 John Wiley & Sons, Inc.
Electronic structure and properties of hexagonal wurtzite‐type SiC
Authors: Ruiz Eliseo , Alvarez Santiago , Alemany Pere 
Published: January 2005

AbstractThe periodic ab initio Hartree–Fock linear combination of atomic orbitals program CRYSTAL has been used to investigate the electronic structure of the wurtzite‐type phase of SiC. Binding energy, lattice parameters (a,c), and the internal cordinate have been optimized. Inclusion of polarization functions, which has been shown to be necessary in the description of related systems, has been used to compute the bulk modulus and its pressure derivative and the central zone A1 transverse optical phonon frequency. The electronic structure of SiC is analyzed using density of states projections and electron density maps. Results are compared with those obtained for the cubic zinc blende‐type phase. © 1994 John Wiley & Sons, Inc.
The onset of classical chaos in atom–surface scattering
Authors: Guantes R. , Borondo F. , Jaffé Charles , Miret‐artés S. 
Published: January 2005

AbstractThe relationship between surface rainbows and the onset of classical chaos in atom–surface scattering is discussed. The principal focus is the onset of chaos as a function of experimentally controllable parameters. The correspondence between the classical trapping and quantum mechanical selective adsorption resonances is briefly discussed. The connection with the more mathematical work of Grebogi and co‐workers is also considered. © 1994 John Wiley & Sons, Inc.
Theoretical study of many‐body effects in the photoelectron spectra of unsaturated hydrocarbons
Authors: Lisini A. , Fronzoni G. , Decleva P. 
Published: January 2005

AbstractA theoretical investigation on the core and valence photoelectron spectra of unsaturated hydrocarbons of increasing complexity, ethylene, trans‐butadiene, and trans‐hexatriene, has been performed in order to analyze the role of the most important many‐body effects on the spectral features and the evolution of these effects along the series. The capability of various configuration interaction (CI) schemes to interpret both the core and the valence ionization satellite structures has been pointed out. The 3h‐2v(π)‐1p and 2h–1p CI schemes employed, together with an accurate choice of the basis set and the explicit inclusion of the relaxation, has proven to be very useful tools for this kind of study, being sufficiently accurate to explain the most important correlation features and extendible, at the same time, to longer chain systems. © 1994 John Wiley & Sons, Inc.
Investigation of the 1E states in cyclic polyenes
Authors: Bracken P. , Čížek J. 
Published: January 2005

AbstractAn analysis withing the one‐dimensional Hubbard model of the 1E type state in cyclic polyenes is reported. In terms of the resonance integral β, a small β analysis and asymptotic large β analysis have been carried out. Energy as a function of β has been calculated numerically, and a second state with 1E symmetry has been found. Some missing information about the higher momentum state of this symmetry is provided. © 1995 John Wiley & Sons, Inc.
Approximate energy‐evaluating schemes for a system of weakly overlapping group functions
Authors: Ferenczy György G. 
Published: January 2005

AbstractThe energy of weakly overlapping group functions can be written as a series according to the powers of the (σ – I) matrix, where σ is the molecular overlap matrix and I is the unit matrix [1,2]. This power series of the energy is studied by investigating the importance of different order terms to obtain accurate energies and to predict equilibrium bond lengths. It is found that the series is truncated advantageously at an even‐order term. Approximate formulas for the first‐ and second‐order terms are proposed in order to reduce computational work. Numerical examples are presented to illustrate the effect of these terms to the energy. The relation of the projection energy to the approximate first‐ and second‐order terms is also discussed. It is found that, by choosing appropriate projection factors, the projection energy corrects the zeroth‐order energy more efficiently than does the first‐order term. The inclusion of the approximate second‐order term represents a slight improvement with respect to the use of the projection energy at the expense of some extra computation. © 1995 John Wiley & Sons, Inc.
“Neglect of Diatomic Differential Overlap” in nonempirical quantum chemical orbital theories. II. A polynomial expansion for Δ−1/2 in terms of Legendre and Chebyshev polynomials
Authors: Neymeyr Klaus , Seelig Friedrich Franz 
Published: January 2005

AbstractSeveral attempts to justify the Neglect of Diatomic Differential Overlap (NDDO) approximation in terms of a power series expansion for Δ−1/2 (Δ is the overlap matrix) have been made (cf. Part I). The new approach for attaining an optimal approximation of Δ−1/2 represented here transfers the problem of finding an optimal matrix polynomial to an approximation problem of real functions within the spectrum of Δ. Best approximations are derived by use of Legendre and Chebyshev polynomials. © 1995 John Wiley & Sons, Inc.
“Neglect of Diatomic Differential Overlap” in nonempirical quantum chemical orbital theories. III. On the spectrum of the overlap matrix for diatomic molecules over locally orthogonalized basis functions
Authors: Neymeyr Klaus , Engel Klaus 
Published: January 2005

AbstractThe sum of the smallest and the greatest eigenvalue of the overlap matrix of diatomic molecules in a basis of locally orthogonalized linearly independent functions is equal to 2. Therewith, polynomial expansion techniques for the justification of the NDDO approximation become identical for diatomic molecules. © 1995 John Wiley & Sons, Inc.
“Neglect of Diatomic Differential Overlap” in nonempirical quantum chemical orbital theories. IV. An examination of the justification of the neglect of diatomic differential overlap (NDDO) approximation
Authors: Neymeyr Klaus 
Published: January 2005

AbstractThe Neglect of Diatomic Differential Overlap approximation is examined in terms of a polynomial expansion in Γ. The expansion is based upon the Legendre or Chebyshev approximation as developed in Part II. Analogous to the theorems of Chandler and Grader, NDDO cannot be justified for one‐electron integrals and only partially for the two‐electron repulsion integrals. © 1995 John Wiley & Sons, Inc.
“Neglect of Diatomic Differential Overlap” in nonempirical quantum chemical orbital theories. V. A calculus of error concerning the justification of the neglect of diatomic differential overlap (NDDO) approximation
Authors: Neymeyr Klaus 
Published: January 2005

AbstractSeveral types of approximations have been used for the justification of the Neglect of Diatomic Differential Overlap (NDDO) in Part IV but control of the introduced error remains insufficient. Analytic formulas describing the induced error for all types of approximations are given. Numerically lower bounds for these errors can be derived from the discussion on diatomic molecules. Far‐reaching consequences on the applicability of NDDO will be discussed. © 1995 John Wiley & Sons, Inc.
Atoms and molecules in cavities: A method for study of spatial confinement effects
Authors: Zicovich‐Wilson C. , Jaskólski W. , Planelles J. 
Published: January 2005

AbstractA general method for solving the problems of spatially confined quantum mechanical systems is proposed. The method works within the framework of the model space approximation. In the case of atoms and molecules trapped into any‐shape microscopic cavity (like molecular sieves or fullerenes), the method reduces to a simple modification of the commonly used basis‐set quantum chemical calculations. The modification consists of a particular rotation and projection in the model space, leading to solutions better adapted to the boundary conditions of the spatial confinement than the functions that describe the free systems. To illustrate how this method works, it has been applied to the hydrogen atom confined in a spherical well, near a hard wall and confined in a cubic box. The results are also compared to the exact solutions. © 1995 John Wiley & Sons, Inc.
Ab initio MO and approximate density functional theory studies on the lowest singlet and triplet states of s and as‐indacene
Authors: Hertwig Roland H. , Holthausen Max C. , Koch Wolfram , Maksí Zvonimir B. 
Published: January 2005

AbstractThe lowest singlet and triplet states of s‐ and as‐indacene have been studied by means of high‐level ab initio MO and approximate density functional methods. Among the geometrical and energetical details discussed are the equilibrium structure of s‐indacene (C2h or D2h), the structures and energies of the low‐lying s‐indacene triplet states, and the stability and geometry of the singlet and triplet states of as‐indacene. It is shown that single‐determinant‐based methods, such as Hartree‐Fock or MP2, are not suited to properly describe these molecules. Instead, methods are required which explicitly take into account nondynamical and dynamical electron correlation. The results obtained by density functional theory‐based methods compare very well with the most elaborate ab initio MO data and seem to provide an economical alternative even for molecules with a complicated electronic structure such as s‐ and as‐indacene. © 1995 John Wiley & Sons, Inc.
Theoretical investigation of cis‐ and trans‐nitric oxide dimers with ab initio and density functional Gaussian‐type orbital approach
Authors: Jursic Branko S. , Zdravkovski Zoran 
Published: January 2005

AbstractStructures and total energies of the cis‐NO dimer, the trans‐NO dimer, and the NO monomer were calculated by ab initio methods (UHF, UMP2, and MP3) and density functional theory methods (LSDA and BLYP) with different basis sets [from 3‐21G* to 6‐311++(3df,3pd)]. The system is especially hard to model because two NO molecules are weakly associated in a dimer that has a very long NN bond. The results obtained by different methods are compared and the necessity of correlational methods for studying these systems is discussed. © 1995 John Wiley & Sons, Inc.
On electron correlation in NaCl2
Authors: Ju Guan‐Zhi , Machado Francisco B. C. , Davidson Ernest R. 
Published: January 2005

AbstractThis article reports the intrapair and interpair electron correlation energies of the radical NaCl2. The total interpair correlation energy dominates. Hence, the interpair electron correlation energy must be considered in building models for correcting computed correlation energies. The 6‐311+G* basis set recovers only 32% of the total estimated correlation energy and 44% of this amount came from the core electrons. © 1995 John Wiley & Sons, Inc.
Über fluorierte Phosphate, Sulfate, Selenate, Tellurate und Dithionate
Authors: Weinland R. F. , Alfa J. 
Published: January 2005

AbstractBei den beschriebenen Fluorphosphaten, Fluorsulfaten, Fluorselenaten, Fluortelluraten und Fluordithionaten gelangt man, wie schon ausgeführt, durch die Annahme, dass sie durch Anlagerung von Fluorwasserstoff an die betreffenden, teils saueren, teils neutralen Salze unter Aufrichtung doppelt gebundener Sauerstoffatome entstanden sind, zu einer einfachen und einheitlichen Vorstellung über ihre Konstitution. Sie erscheinen so als mehr oder weniger vollständig hydroxylierte Salze, in denen eine oder mehrere Hydroxylgruppen durch Fluor ersetzt sind.
Über das sogenannte elektrolytische Silbersuperoxyd. (Zweite Mitteilung)
Authors: Šulc Ot. 
Published: January 2005

AbstractZusammenfassungDurch die vorliegende Arbeit glaube ich dargethan zu haben, dass die bei der Elektrolyse von wösserigen Silbernitratlösungen zwischen Platinelektroden an der Anode sich bildende krystallinische Substanz von der Formel Ag7NO11, beim Erhitzen nach und nach 5 Atome Sauerstoff verliert, 80 dass ein Komplex Ag7NO6 zürlickbleibt, welcher als AgN03.3Ag2O anzufassen ist.
Beiträge zur Kenntnis der Tellursäure
Authors: Gutbier A. 
Published: January 2005

Abstract1. Es ist zu empfehlen, das ungarische Rohtellur nicht als solches nach der von STAUDENMAIER angegebenen Methode auf Tellursäure zu verarbeiten, sondern das Tellur erst aus dem rohen Produkte abzuscheiden.2. Die Methode, die Tellursäure in Gestalt ihres Baryumsalzes abzuscheiden, ist zu verwerfen.3. Die yon BERZELIUS beschriebene Säure H2TeO4 existiert nicht; sie ist ein Gemenge von H6TeO6 mit TeO3, öfters mit TeO2 verunreinigt.
Die Einwirkung von Magnesiumoxyd auf ein Gemisch von Arsentrisulfid und Schwefel
Authors: Foster William 
Published: January 2005

AbstractBei der Einwirkung von Magnesia auf ein Gemisch von Arsentrisulfid und Schwefel in wässeriger Suspension entsteht eine Reihe von Verbindungen, deren Mengenverhältnis von den herrschenden Versuchsbedingungen: Temperatur, Schütteln, Zeitdauer, möglicherweise auch von der Wassermenge abhängt.
Über das Verhalten einiger Zirkonsalze und die Konstitution des neutralen Zirkonsulfats
Authors: Ruer Rudolf 
Published: January 2005

AbstractDer wesentliche Inhalt der vorliegenden Mitteilung ist folgender:1. Neutrales Zirkonsulfat gibt die charakteristischen Reaktionen mit Oxalsäure und oxalsaurem Ammoniak, wie sie beim Chlorid und Nitrat auftreten, nicht.2. Zusatz von neutralem Ammoniumsulfat resp. Natriumsulfat zu frisch bereiteten Zirkonoxychloridlosungen bewirkt ebenfalls das Ausbleiben dieser Reaktionen.3. Der Grund für das abweichende Verhalten des Sulfats kann daher nicht in dem höheren Säuregehalte des Sulfats gegenüber dem Oxychlorid gesucht werden, man muss vielmehr dem Zirkonsulfat in wässeriger Losung eine von der des Chlorids und Nitrats abweichende Konstitution zuschreiben. Das Verhalten des neutralen Zirkonsulfats in wässeriger Lösung kann am besten durch die Formel

ausgedruckt werden.
Einige Bestimmungen in den Systemen: KJO3HJO3H2O, NaJO3HJO3H2O und NH4JO3HJO3H2O
Authors: Meerburg P. A. 
Published: January 2005

Abstract1. Die Isothermen für 30° werden in den ternären Systemen: (KJO3HJO3H2O), (NaJO3HJO3H2O) und (NH4JO3HJO3H2O) bestimmt.
Über das Verhalten des Selens gegen Licht und Temperatur. III. Mitteilung
Authors: Marc Robert 
Published: January 2005

Abstract1. Es wurde konstatiert, dass die Form A des schwarzen kristallinischen Selens praktisch ein Nichtleiter ist, und dass die scheinbare Leitfähigkeit mit positivem Temperaturkoeffizienten geringen Mengen von SeO2 zuzuschreiben ist.
Über die Einwirkung von Kohlendioxyd auf wässerige Bleiacetatlösungen
Authors: Altmann Artur 
Published: January 2005

AbstractEs wurden im ersten Hauptteil der Arbeit die Beziehungen der Niederschlagsmenge an Bleikarbonat zu Temperatur und Konzentration der Bleizuckerlösungen untersucht und gefunden, dass die Fällungen mit abnehmender Konzentration stets wachsen, nicht so regelmäßig aber mit abnehmender Temperatur.
Über den Farbenwechsel von Kobalt‐ und Kupferchlorid in Lösung
Authors: Benrath Alfred 
Published: January 2005

AbstractDie oben angestellten Betrachtungen stützen die Hartley Lewissche Hydrattheorie. Der Farbumschlag von Kobalt‐ und Kupferchloridlösungen beruht nicht auf Komplexbildung, sondern auf der Bildung niederer Hydrate, sowohl in reinem Wasser als auch in Gegenwart von Chloriden. Nur Chloride, welche den Farbumschlag verhindern, bilden mit den in Frage kommenden Chloriden komplexe Salze. Alkohole bilden Alkoholate.
Zur Formulierung von Mercurochlorid, ‐bromid, ‐jodid, Cuprochlorid, sowie von Chloriden des Thalliums und der Alkalien
Authors: Beckmann Ernst 
Published: January 2005

AbstractFür die Mercurohalogenverbindungen sind die folgenden Formeln bestätigt worden: Hg2Cl2, Hg2Br2, Hg2Jg2.