bluuebunny/crossref_metadata_2025_split huggingface dataset:
Influence of Tester Geometry, Speed and Procedure on the Results from a Ring Shear Tester
Authors: Schmitt Rüdiger , Feise Hermann 
Published: January 2005

AbstractAutomated ring shear testers have gained widespread acceptance in the chemical industry. In this paper, comparative measurements with different shear testers are described and possible factors influencing the measurement of flowability, are discussed. The measurement results presented show a dependency on the bulk solid investigated. No significant influence of the shear tester was measured for easy flowing bulk solids. An influence of the shear tester is observed for poor flowing, compressible bulk solids. Experiments have shown that test procedure and shear cell design (tester geometry) affect the measurements considerably.
Nonlinear current–voltage characteristics and recombination current instability in p‐Ge(Au)
Authors: Kamilov I. K. , Ibragimov Kh. O. , Aliev K. M. , Abakarova N. S. 
Published: January 2005

AbstractResults of an experimental study of short and long p‐Ge(Au) samples are presented and compared qualitatively with data furnished by the one‐dimensional theoretical model describing the evolution of domain instability in a two‐parametric space “voltage V–emission coefficient β”. According to the theory, single, double‐ and multi‐subdomain states and order–disorder–order transitions via intermittency have been observed in the system with increasing voltage. Three operation regimes of the system are found, depending on the region of the parametric space: ohmic, quenched (pulsing) and transit‐time. In short samples a second portion with S‐switching is revealed in the current–voltage characteristic. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Ionic conduction studies in P(VDF–HFP)–LiAsF6–(PC + DEC)–fumed SiO2 composite gel polymer electrolyte system
Authors: Saikia D. , Kumar A. 
Published: January 2005

AbstractIn the present work, thin polymer electrolyte films of P(VDF–HFP) copolymer containing LiAsF6 salt dissolved in PC and DEC and fumed SiO2 submicron particles as dispersed phase prepared by solution casting technique are characterized by ac impedance measurements in the temperature range 303 K–373 K. Maximum ionic conductivity for P(VDF–HFP)–(PC + DEC)–LiAsF6–SiO2 fumed composite gel polymer electrolyte is found to be of the order of 10–3 S/cm at room temperature. XRD patterns show the increased amorphicity in the electrolytes. The degree of crystallinity is decreased from 30% in pure polymer to 17.7% in composite gel polymer electrolyte. Scanning electron micrographs show uniform dispersion of SiO2 particles and suggest that SiO2 supports formation of porous microstructures and increases the retaining capability of liquid electrolyte in the polymer gel network. FTIR spectral analyses confirm the polymer/salt/filler interaction. (© 2005 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)
Bonding of Cr and V in FeAl B2 phase
Authors: Fuks D. , Strutz A. , Kiv A. 
Published: January 2005

AbstractAb initio calculations of the properties of the FeAl B2 phase alloyed by Cr or V are performed on the basis of the full potential augmented plane‐wave (APW) + local orbitals (lo) method. The site preference occupation for Cr and V atoms in this compound is investigated. We studied the changes in the site preference for Cr and V substituting for Fe or Al when the vacancy on the Fe site is formed. Existence of the vacancy significantly changes the site occupation preference for Cr that transits from the Al site to the Fe site. The site occupation preference for these alloying elements in the compound is explained in terms of the electronegativity of surrounding atoms and the effective charges of transition metals. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Refractive index and third‐order nonlinear susceptibility of C60 in the condensed phase calculated with the discrete solvent reaction field model
Authors: Jensen L. , Van Duijnen Piet Th. 
Published: January 2005

AbstractWe have calculated the frequency‐dependent refractive index and the third‐order nonlinear susceptibility for C60 in the condensed phase, which is related to third‐harmonic generation (THG) and degenerate four‐wave mixing (DFWM) experiments. This was done using the recently developed discrete solvent reaction field (DRF) model, which combines a time‐dependent density functional theory (TD‐DFT) description of the central C60 molecule with a classical polarizable MM model for the rest of the fullerene cluster. Using this model, effective microscopic properties can be calculated that, combined with calculated local field factors, give macroscopic susceptibilities. The largest calculation was for a cluster of 63 C60 molecules in which the central molecule was treated with TD‐DFT. For this molecule, the effective polarizability was increased with about 15% and the effective second hyperpolarizability with about 60% compared with the gas phase. The calculated refractive index was found to be in good agreement with experiments and other theoretical results. The agreement with THG experiments was within a factor of two, whereas for DFWM the agreement was less good due to the neglect of vibrational contributions in the calculations. It was found that it is more important to account for the dispersion in the third‐order susceptibilities than in the corresponding second hyperpolarizability. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Computational study of dimethyl phosphate anion and its complexes with water, magnesium, and calcium
Authors: Petrov Anton S. , Funseth‐Smotzer Joni , Pack George R. 
Published: January 2005

AbstractDimethyl phosphate anion (DMP−) is often used to simulate the properties of the phosphate group, an important structural fragment of nucleic acids and phospholipids. Besides its functional importance, DMP− has a strong affinity for metal cations and is often considered to be their binding site. In this study we reevaluate the binding properties of DMP− with water molecules and with explicitly hydrated magnesium and calcium cations in the presence of a polar continuum solvent. We analyze the stability of the DMP− in different conformations that represent possible inner‐ and outer‐sphere binding modes. Our previous work (Petrov et al. J Phys Chem B 2004) has shown that electrostatic calculations, particularly those using a point‐charge model, are wholly inadequate for this purpose. Calculations were performed at the B3LYP/6‐31G(d,p) level of theory within the framework of the COSMO polarized continuum model (CPCM). Our data indicate that magnesium prefers outer‐sphere coordination with DMP−, whereas calcium binds directly. The effect of cation binding on vibrational infrared and Raman spectra are also discussed. We found that the inclusion of polar solvent in the computations improves the agreement between calculated spectral data and experimental results. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
Theoretical studies on cosolvation of Li ion and solvent reductive decomposition in binary mixtures of aliphatic carbonates
Authors: Wang Yixuan , Balbuena Perla B. 
Published: January 2005

AbstractWe use density functional theory to investigate the interactions of Li+ and aliphatic carbonates such as ethylene carbonate and three linear carbonates (dimethyl, diethyl, and ethyl methyl), and the reductive decomposition mechanisms of these carbonates. On the basis of theoretical results and analyses, some phenomena relevant to the formation of a solid electrolyte interphase layer at the electrode surface of lithium ion batteries are well explained. This study also illustrates that theoretical analyses and calculations are able to provide useful insights into the design of components for modern power systems. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005
New unitary transformation for the three coupled oscillators
Authors: Hong‐Yi Fan 
Published: January 2005

AbstractA new unitary operator U, which can transform the Fock space of a three‐dimensional isotropic harmonic oscillator into the space in which the Hamiltion of three coupled oscillators is diagonized, is found. The coordinate representation of U is presented and is used to directly derive the wave function of the energy eigenstate of the coupled oscillators.
Explicit density–potential relation for 4‐electron atoms in 2‐orbital S states
Authors: Hunter G. , March N. H. 
Published: January 2005

AbstractAn explicit relation is derived between the one‐body potential energy and the electron density for the ground state of the Be atom in a nonrelativistic framework. This same relation applies to any four‐electron atomic ion (or to Be itself) in a state where the electrons occupy two doubly filled orbitals. The relation is interpreted as an exact Hartree‐like model of the Hohenberg–Kohn theorem within the general context of N electrons and a potential that is not necessarily spherically symmetrical.
Electronic structure of helium‐trapped vacancy in aluminum using multiple scattering Xα method
Authors: Iyakutti K. , Sankar S. , Thiagarajan M. 
Published: January 2005

AbstractThe self‐consistent multiple scattering Xα (MSXα) method is used to arrive at the electronic structure of a helium‐trapped vacancy in aluminum using a cluster model. The calculated orbital energies, electron density, and charge distributions are compared with the available theoretical results. It is shown that helium trapping causes the reshuffling and upward movement of the cluster levels (with vacancy).
Analysis of degeneracy in the spectrum of a class of molecular graphs
Authors: Ojha P. C. 
Published: January 2005

AbstractWe consider the Hückel approximation to the π‐electron spectrum of molecules which are built by linking a number of identical fragments to a central atom in an identical manner. The Hückel matrix H of the composite molecule (or equivalently the adjacency matrix of the molecular graph) is simply related to the Hückel matrix h of the fragment and a vector \documentclass{article}\pagestyle{empty}\begin{document}$ vec{f} $\end{document} which encodes the bonding of a fragment to the central atom. The eigenvalues and eigenvectors of H are obtained from those of h. The orbitals of the composite molecule are of three types: (1) a molecular orbital of the fragment localized on one of the fragments, (2) a molecular orbital of the fragment spread over more than one fragment, and (3) orbitals spread over the entire molecule including the central atom. The orbital energies Λ of the first two types of orbitals are same as the orbital energies λ of the fragment. Energies of the third type of orbitals separate a subset of orbital energies of the fragment and, barring accidental degeneracy, they are distinct from all orbital energies of the fragment. It is only through the third type of orbitals that the composite molecule manifests itself as a new entity rather than an aggregate of noninteracting fragments. It is shown that the graph group of H fails to explain its degeneracy if any eigenvector of the subgraph, not orthogonal to the connection vector \documentclass{article}\pagestyle{empty}\begin{document}$ vec{f} $\end{document}, belongs to a degenerate manifold of h. This solves a long‐standing puzzle regarding degeneracy in the Hückel spectrum of triphenylmethyl.
Algebrants in many‐electron quantum mechanics: Applications of generalized determinants or matrix functions
Authors: Poshusta R. D. , Kinghorn D. B. 
Published: January 2005

AbstractWe define the algebrant, a mathematical generalization of the determinant, the immanant, the permanent, and the Schur functions. Algebrants are classified as multilinear matrix functions or multicomponent symmetrized tensors. In applications, such as N‐electron quantum mechanics, where extensive computation is required, it is vital to reduce computational effort, e.g., the well‐known N‐factorial problem. We derive certain mathematical properties that can be incorporated in efficient computing algorithms for algebrants. Foremost is our “elimination theorem,” which allows (in important special cases) zeros to be introduced into an algebrant in close analogy with Gaussian elimination for determinants. Savings accruing from such elimination can be substantial. We show examples from Matsen's spin‐free quantum chemistry where elimination effectively removes the N‐factorial problem that has hitherto stifled possible applications.
Symmetric‐group algebraic variational solutions for Heisenberg models at finite temperature
Authors: Klein D. J. , Seitz W. A. 
Published: January 2005

AbstractThe Heisenberg spin Hamiltonian for a collection of N spin‐1/2 sites is viewed, as favored by Professor Matsen, to be an element of the group algebra of the symmetric group 𝒮N. Several computationally tractable, variational group–algebraic approximations for the finite‐temperature density matrix are made so as to minimize the Gibb's free–energy functional. Relations to previous quite differently motivated approximations are identified, though improvements are noted with the present approach.
The Berry phase in molecular physics
Authors: Bohm A. , Kendrick B. , Loewe Mark E. 
Published: January 2005

AbstractThe geometric phase of quantum mechanics is introduced, and its physical effects are then studied in the context of molecular physics. By performing the most general Born–Oppenheimer procedure, we show how gauge groups appear in the study of molecules. This method is then applied to the doubly degenerate Λ‐levels of a diatomic molecule. The resulting dynamics for the slow angular motion of the dumbbell is equivalent to that of a Dirac monopole.
On the internally contracted multireference CI method with full contraction
Authors: Siegbahn Per E. M. , Svensson Mats 
Published: January 2005

AbstractThe configuration interaction (CI) method where the efficiency of the generators of the unitary group is most fully exploited is the internally contracted multireference CI method. In the most recent version of this method the semi‐internal configurations were kept uncontracted, which means that the number of configurations can still be quite large. In the present study the necessary formulas are derived for the case where the semi‐internal states are also contracted. The highest density matrix that appears in these formulas is of order 5, and the computational treatment of this large matrix is discussed in detail.
Improved quadrature methods for the Fourier transform of a two‐center product of exponential‐type basis functions
Authors: Homeier Herbert H. H. , Steinborn E. Otto 
Published: January 2005

AbstractThe numerical properties of a one‐dimensional integral representation [H. P. Trivedi and E. O. Steinborn, Phys. Rev. A 27, 670 (1983)] for the Fourier transform of a two‐center product of certain exponential‐type orbitals (ETOs), the B functions [E. Filter and E. O. Steinborn, Phys. Rev. A 18, 1 (1978)], are examined. These functions span the space of ETOs. Hence, molecular integrals for other ETOs, like the more common Slater‐type orbitals, may be found as finite linear combinations of integrals with B functions. The main advantage of B functions is the simplicity of their Fourier transform that makes the derivation of relatively simple general formulas for molecular integrals with the Fourier transform method possible. The integrand of the integral representation mentioned above shows sharp peaks, making, in the cases of highly asymmetric charge distributions and/or large momentum vectors, usual quadrature methods rather slow. New quadrature schemes are presented that utilize Möbius‐transformation‐based quadrature rules. These rules are well suited for the numerical quadrature of functions possessing a sharp peak at or near one boundary of integration [H. H. H. Homeier and E. O. Steinborn, J. Comput. Phys. 87, 61 (1990)]. Numerical results are presented that illustrate the fact that the new quadrature schemes are much more efficient than are automatic quadrature routines.
Theoretical prediction of ionization potential, electron affinity, and electronic spectrum of the S2N radical
Authors: Sannigrahi A. B. , Peyerimhoff S. D. 
Published: January 2005

AbstractAb initio MRD–CI calculations using a basis set of near Hartree–Fock quality have been carried out to calculate the ground‐state electronic structure of S2N+, S2N, and S2N− and the ionization potential, electron affinity, and vertical electronic spectrum of S2N. At the highest level of theory (estimated full CI or FCI), S2N+ is predicted to have a linear structure with r(NS) = 1.51 Å. For S2N and S2N−, the minimum in energy at the FCI level corresponds to a quasi‐linear [with a barrier height to linearity of about 2.0 kcal mol−1, ] and a bent structure , respectively. The adiabatic/vertical ionization potential and electron affinity of S2N are predicted to be 7.26/7.82 and 1.60/0.79 eV, respectively. Of the several electronic transitions in S2N considered, the ones with the excitation energy of 1.87 eV (X2 A1 → 2B2) and 2.87 eV (X2A1 → 2B2) are somewhat intense (ƒ = 0.005 and 0.002) and likely to be observed.
Modification of the superposition of correlated configurations method
Authors: Firszt M. , Woźnicki W. 
Published: January 2005

AbstractIntroduction of a modified correlation factor in the place of r eliminates the problem of multiple infinite summations in Hamiltonian matrix elements. Calculations performed for several He states show that the introduction of the modified correlation factor does not change energies of the states by more than 1 cm−1.
A quantum chemical study of interchain hopping model of negatively charged solitons in polyacetylene
Authors: Tachibana Akitomo , Ishikawa Shigeru , Asai Yoshihiro , Katagiri Hideki , Yamabe Tokio 
Published: January 2005

AbstractPhonon‐assisted interchain hopping of negatively charged solitons in polyacetylene has been studied using a local chemical reaction model CH + CH4 → CH4 + CH. Quantum chemical characteristics of the electron transfer process have been analyzed in terms of the dynamic electron density and the mutual polarization moment. The CH stretching vibrational motion of CH4, which is a local model of the sp3 defect, has been found to play a significant role for the electron transfer. The excitation of the corresponding vibrational mode of the sp3 defect would promote the interchain hopping of the charged soliton. The electron transfer process has also been studied in terms of the “regional” density functional theory. It has been shown that the driving force of the electron transfer is represented by the regional chemical potentials.
Accurate local spin‐polarized exchange potential: Reconciliation of generalized Slater and Kohn–Sham methods
Authors: Krieger J. B. , Li Yan , Iafrate G. J. 
Published: January 2005

AbstractUsing simple physical arguments, a local spin‐polarized exchange potential, Vxσ, is constructed from the single‐particle Hartree–Fock (HF) potentials (generalized Slater method) that reduces to the usual Kohn–Sham (KS) result in the uniform gas limit. Numerical results for 10 closed subshell atoms demonstrate that the total energy calculated employing this Vxσ is closer to the exact KS results than those of other standard exchange approximations with electron densities and highest occupied orbital eigenvalues that closely approximate the HF results.
Computational studies of the 3‐Dimensional structure of cyclopenta polycyclic aromatic hydrocarbons containing a gulf region
Authors: Venegas Ruben E. , Reggio Patricia H. , Rabinowitz James R. 
Published: January 2005

AbstractRecently, some cyclopenta‐fused polyaromatic hydrocarbons, an environmentally relevant subclass of chemicals, have been shown to have carcinogenic activity in animals. It has been suggested that benz[l] aceanthrylene (I), an active member of this subclass with a gulf region, has a trans dihydrodiol metabolite that is nonplanar and has two distinct spatial configurations. We have used MMP2(85) and AM1 to investigate the three‐dimensional structure of this dihydrodiol and other similar derivatives of (I) and have found that although (I) is somewhat nonplanar the relevant derivatives are all nearly planar. Further, we have computed potential functions for the bending of the angular ring in the gulf region using MMP2(85), AM1, and ab initio computed energies for AM1 spatial configurations and find that these molecules all have only a single potential minimum. We have performed the same calculations for benzo[c]phenanthren and its 1,12 dimethyl derivative, molecules with a similar gulf region for which crystallographic data exists. In agreement with that data, we find that two distinct spatial configurations exist separated by significant barries. The differences between the results generated by the three different methods of computation will be discussed.
The application of the graph‐theoretical method in the QSAR scheme: Possibilities and limits
Authors: Romanowska Krystyna 
Published: January 2005

AbstractThe correlation between topological features of molecular structure and physicochemical as well as biological properties of molecules were examined for some sets of compounds, using graph–theoretical desciptions. It was found that the topological similarity plays a role in the determination of molecular properties for almost all compound sets studied. As a conclusion, one can presume that the less elaborated and complicated similarity measure based on the graphtheoretical description is sufficient in the case of distinct structure–property dependence.
Molecular structure and polarity of the C3NH carbene
Authors: Da Silva João Bosco P. , Ramos Mozart N. 
Published: January 2005

AbstractAb initio MP2/4‐31G** calculations indicate that the most stable form of C3NH is bent and singlet and that the linear structure corresponds to a maximum. The effect of changing the CNH angle on the total energy is slight, but it is quite pronounced on the molecular polarity. The wider angle tends to increase the polarity of C3NH. MP2/4‐31G** calculations predict a difference of polarity between linear and bent structures of 0.8 D.
Formulation of the coupled cluster theory with localized orbitals in correlation calculations on polymers
Authors: Förner Wolfgang 
Published: January 2005

AbstractIt is shown that in the framework of coupled cluster theory both the correlation energy per unit cell and quasi‐particle band structures of polymers can be computed directly from matrix elements of the excitation operator and the two‐electron integrals calculated in localized orbital basis. Further, it is described how to thake advantage of the localized nature of the orbitals applied. Ab initio test calculations on a finite model system similar to the Pariser–Parr–Pople Hamiltonian are presented.
Computation of two‐, three‐, and four‐center exchange integrals over Slater basis by means of optimized Gaussian expansions
Authors: Montagnani Raffaele , Salvetti Oriano 
Published: January 2005

AbstractA new way of computing two‐electron integrals over Slater functions by means of optimized Gaussian expansions is proposed. Expansions up to five terms have been optimized for 1s, 2s, and 2p STOs and applied to the computation of many‐center two‐electron integrals. All these integrals can be quickly evaluated and the SCF energy computed from them is very accurate.
Linear dependence in basis‐set calculations for extended systems
Authors: Aissing Gerrard , Monkhorst Hendrik J. 
Published: January 2005

AbstractThe problem of linear dependence in basis‐set calculations for extended systems is discussed. We show that the problem is intrinsic in three‐dimensionally extended systems, but is not as serious in systems with extension in fewer dimensions. The possibility of choosing suitable basis sets that avoid linear dependence is discussed. It is shown that for systems extended in three dimensions in which the orbitals near the Fermi‐level are well described by plane waves a mixed atomicorbital/plane‐wave (AO–PW) basis set with tight orbitals to describe the cores avoids the problem in the most efficient way. Numerical experiments with 1s Slater‐type orbitals and plane waves on a simple cubic lattice are presented for illustration. © 1992 John Wiley & Sons, Inc.