bluuebunny/crossref_metadata_2025_split huggingface dataset:
Electronic structure and hyperpolarizability of some conjugated molecules in excited states
Authors: Kanev Ivo 
Published: January 2005

AbstractFor the examples of aromatic and antiaromatic five‐membered heterocycles, the static electronic polarizabilities and hyperpolarizabilities are determined in the ground and first singlet‐ and triplet‐excited electronic states. The theoretical calculations are carried out in the SOS formalism and the correlation effects are taken into account using all mono‐ and biexcited configuration in the PPP approximation. It is shown that the singlet excitation of the molecules for the antiaromatic case is connected to an significant decrease of both polarizabilities and hyperpolarizabilities. Their values are discussed in terms of the index of average bond‐order alternation for the ground and excited states and the localization of the electronic transitions in the molecules. © 1993 John Wiley & Sons, Inc.
Ab initio studies on the IRC and rate constant of the reaction between acetylene and the hydrogen atom
Authors: Fang De‐Cai , Fu Xiao‐Yuan 
Published: January 2005

AbstractThe geometries of the reactant, product, and transition state of the reaction between acetylene and the hydrogen atom have been optimized at the level of HF/6‐31G using the energy gradient method. The barrier height for this reaction was calculated to be 105.9 kJ/mol with a zero‐point energy correction and elimination of spin contamination. The intrinsic reaction coordinate (IRC) for this reaction was traced and the coupling between the IRC and normal modes was analyzed along the IRC. The variational transition‐state theory with the correction of the tunnel effect has been used to evaluate the reaction rate constant. It is in good agreement with an experimental estimate. © 1994 John Wiley & Sons, Inc.
On the relation between the Kratzer molecular potential and a set of displaced morse oscillator potentials
Authors: Cooper Ian L. 
Published: January 2005

AbstractThe radial Schrödinger equation for the Kratzer molecular potential is equivalent to that of a radial Coulomb problem with an effective (nonintegral) value of rotational angular momentum. The radial Coulomb and the Morse oscillator problems provide different realizations of the algebra so(2,1), whereby the Casimir operators of the Coulomb and Morse oscillator problems are related to the angular momentum quantum number and to the energy, respectively. These relationships permit mappings between the Kratzer molecular potential and the Morse oscillator potential such that the vibrational energy levels of a Kratzer potential with a fixed rotational angular momentum quantum number may be mapped onto degenerate vibrational levels of a set of displaced Morse oscillators. The ground vibrational level of the Kratzer potential is mapped onto the ground vibrational level of a specific Morse oscillator and the remaining (infinite) set of higher vibrational levels are mapped onto degenerate states of displaced Morse oscillators, corresponding to systematic unit increase in the number of bound vibrational levels and successive decrease in equilibrium separation. This behavior is contrasted with that of the finite set of displaced Morse potentials arising as supersymmetric partner potentials to a given parent Morse potential, where there is a systematic unit decrease in the number of bound vibrational levels and a successive increase in equilibrium separation. © 1994 John Wiley & Sons, Inc.
Chemistry and electronegativity
Authors: Allen Leland C. 
Published: January 2005

AbstractThis article addresses the chemical aspects of electronegativity: (1) What is its present status in the chemical community? (2) What are the necessary chemical criteria for a quantitative definition? (3) To what extent do contemporary proposals satisfy these criteria? (4) What connection can be made between the traditional free‐atom scales and an in situ electronegativity appropriate for a particular atom in a specific molecule or solid? A longstanding special feature of electronegativity has been the seeming inability to measure it in the laboratory and this aspect proves to be a key to its definition. © 1994 John Wiley & Sons, Inc.
Why define atoms in real space?
Authors: Bader Richard F. W. 
Published: January 2005

AbstractThe physics of a system is determined by a variation of the action integral, i.e., by a variation of the space–time volume integral of the Lagrange function. If one demands that the properties of an atom in a molecule be derived from physics, the atom must generate its own space–time volume, requiring that its boundaries be defined in real space. The variations in the action are related to the actions of generators of infinitesimal unitary transformations. In the general case, the action integral is altered by generators acting in both the spacelike and timelike surface bounding the space–time volume, whereas for a total isolated system, the physics is totally determined by their action in just the spacelike surfaces at the two time endpoints. It is shown and illustrated for a one‐dimensional system that the definition of an atom corresponds to the possibility of choosing a subsystem in such a way that the contributions to the change in action resulting from the evolution in time of its spatial boundaries vanishes identically. The properties of these subsystems and of the total system of which they are a part are, therefore, determined by one and the same action principle. This choice of subsystem corresponds to the possibility of augmenting the Lagrange function by the divergence of the gradient of the electron density a step that, while leaving the equations of motion unchanged, modifies the generating operators in the required manner. © 1994 John Wiley & Sons, Inc.
Theory of relaxed density matrices: Application to second‐order response properties
Authors: Cybulski Slawomir M. , Bishop David M. 
Published: January 2005

AbstractThe evaluation of second derivatives of the electronic energy for nonvariational wave functions using an energy functional is discussed. It is shown that, in certain cases, the formation of the first‐order relaxed density matrix leads to an efficient algorithm for the calculation of second‐order response properties. Detailed formulas are given for second‐order Møller–Plesset perturbation theory. © 1994 John Wiley & Sons, Inc.
Electronic structure of the benzene–tetracyanoethylene complex: A synthesis of molecular orbital and density functional descriptions
Authors: Cioslowski Jerzy 
Published: January 2005

AbstractThe electronic structure of the benzene–tetracyanoethylene electron donor–acceptor complex is investigated at theHF/6‐311G**level of theory. The computed electronic wave function is analyzed with rigorous interpretive tools that involve both molecular orbital and density functional approaches. Thein situelectronegativity difference is calculated at 3.32 eV, resulting in a charge transfer of 0.016. This extent of charge transfer is found to account for only ca. 17% of the interaction energy of ca. 33% of the dipole moment. The remaining part of the dipole moment originates from buckling of the tetracyanoethylene moiety. The dependence of the electronegativity difference on the magnitude of charge transfer is found to be highly nonlinear. © 1994 John Wiley & Sons, Inc.
Ab initio study of the low‐lying electronic states of the CH2NO2 radical
Authors: Cai Z.‐L. 
Published: January 2005

AbstractAb initio electronic structures calculations are reported for the four low‐lying electronic states X 2B1, 2B2, 2A2, and 2A1 of the CH2NO2 radical. The geometric parameters for the ground‐state X 2B1 are predicted by MRSDCI calculations with a double zeta plus polarization basis set. The vertical excitations energies for these electronic states are determined using MRSDCI/DZ+P calculations at the ground‐state equilibrium geometry and in agreement with the recent experimental data obtained via PES of the CH2NO anion. The oscillator strenghts and the radiative lifetimes for these electronic states and the spin properties for the ground state are calculated based on the MRSDCI wave functions, predicting results in good agreement with available experimental data. © 1994 John Wiley & Sons, Inc.
Optimized triple‐zeta Gaussian basis sets for use with relativistic effective potentials
Authors: Pacios L. Fernández , Gómez P. C. 
Published: January 2005

AbstractContracted split valence 311 Gaussian basis sets optimized for the averaged relativistic effective potentials (AREP) of Christiansen et al. are developed for the main‐group elements BNe, AlAr, and GaKr. These triple‐zeta basis sets are intended for use in valence‐only molecular calculations with inclusion of correlation. The performance of the optimized basis functions is first analyzed in HF atomic calculations and compared with HF‐limit results. Molecular calculations at the HF, MP2, and CISD levels of theory are performed for some selected diatomics, using these potentials and the optimized sets supplemented by one standard d‐type polarization function. Results are reported for bond lenghts, harmonic vibrational frequencies, dipole moments, atomization energies, and ionization energies and compared with all‐electron reference calculations and experimental data. © 1994 John Wiley & Sons, Inc.
Molecular cyclicity and centricity of polycyclic graphs. I. Cyclicity based on resistance distances or reciprocal distances
Authors: Bonchev Danail , Balaban Alexandru T. , Liu Xiaoyu , Klein Douglas J. 
Published: January 2005

AbstractRules for molecular cyclicity based on the global indices resulting from reciprocal distances (Harary number, H) or from resistance distances (Kirchhoff number, Kf) were tested in comparison with those elaborated earlier by means of the Wiener index, W. The Harary number and the Wiener number were found to match molecular cyclicity in an almost identical manner. The Kirchhoff number also generally follows cyclicity trends described previously. H is slightly less degenerate than is W, but Kf has practically no degeneracy in the graphs investigated here. Being much more discriminating than the Wiener number (i.e., practically nondegenerate), Kf allowed the formulation of new rules for systems formed from linearly condensed ribbons of even‐membered rings with different sizes as well as for branched ribbons. The topological cyclicity patterns are thus reformulated in an extended basis, proceeding from three different graph metrics. © 1994 John Wiley & Sons, Inc.
Correlated polarization propagator calculations of static polarizabilities
Authors: Sauer Stephan P. A. , Oddershede Jens 
Published: January 2005

AbstractWe present a systematic comparison of the correlation contribution at the level of the second‐order polarization propagator approximation (SOPPA) and MP2 to the static dipole polarizability of (1) Be, BeH−, BH, CH+, MgH−, AIH, SiH+, and GeH+; (2) BH3, CH4, NH3, H2O, HF, BF, and F2; and (3) N2, CO, CN−, HCN, C2H2, and HCHO. Fairly extended basis sets were used in the calculations. We find that the agreement with experimental values is improved in SOPPA and MP.2 over the results at the SCF level. The signs and magnitudes of the correlation contribution in SOPPA are similar to those obtained in analytical derivative MP2 calculations. However, it is not possible to say, in general, which method gives the largest correlation contribution or the best agreement with experiment, nor is it possible to make a priori prediction of the sign of the correlation contribution. For the first group of molecules, which have a quasi‐degenerate ground state, additional CCDPPA and CCSDPPA calculations were performed and compared with polarizabilities obtained as analytical/numerical derivatives of the CCD and CCSD energies. The CCSDPPA results were found to be in better agreement with other calculations than were the SOPPA results, demonstrating the necessity of using methods based on infinite‐order perturbation theory for these systems. © 1994 John Wiley & Sons, Inc.
Ground‐state correlation energy of Ne
Authors: Noro Takeshi , Ohtsuki Kazumasa , Sasaki Fukashi 
Published: January 2005

AbstractA series of basis sets and configuration interaction (CI) wave functions, both of which were constructed so as to systematically approach to the complete set limit and the full CI limit, were used for the ground state of Ne. These calculations yielded an estimated correlation energy of −0.3891 au, which is 99.6% of a recent theoretical estimate of −0.3905 au. The CI value, −0.3821 au, was obtained by SDCI calculation with seven reference configurations by using Slater‐type orbitals (STOs) from s to h functions. © 1994 John Wiley & Sons, Inc.
A density functional elongation method for the theoretical synthesis of aperiodic polymers
Authors: Aoki Yuriko , Suhai Sándor , Imamura Akira 
Published: January 2005

AbstractThe elongation method, a theoretical tool to synthesize the electronic states of polymers, is applied within the framework of the density functional approach and using a linear combination of Gaussian‐type orbitals. In this treatment, the wave function of a cluster is localized and the interaction with an attacking monomer is self‐consistently calculated according to the Kohn–Sham equation. The reliability and the applicability of our treatment are examined by the application to a random hydrogen molecule cluster, comparing the results with those obtained by the usual diagonalization method for the whole system. The results show that this treatment efficiently provides the electronic states of the end part of aperiodic polymers. © 1994 John Wiley & Sons, Inc.
Recent developments in the theoretical design of low‐gap polymers and their nonlinear optical properties
Authors: Otto P. 
Published: January 2005

AbstractGeometry optimizations on molecular clusters of the five‐membered heterocyclic molecules pyrrole, furane, thiophene, and selenophene were carefully carried out. It is shown that the value of the band gap cannot be related to the bond alternation in the aromatic compounds. However, a correlation of the gap value with the ionization potential of the heteroatom in the ring is found and can be explained by the different stabilizations of the LUMO energy of the heterocycle with respect to the butadiene backbone. The energy band structure including also corrections for the electron correlation effects is reported. The newly developed variational method for the calculation of static polarizabilities of polymers is reviewed and applications to cyclopropene and heteroaromatic derivatives are reported. Finally, a possible approach to treat dynamical polarizabilities of polymers based on perturbation theory is briefly outlined. © 1994 John Wiley & Sons, Inc.
Theory of hopping conductivity of proteins
Authors: Ye Yuan‐jie , Ladik János 
Published: January 2005

AbstractQuantum chemical calculations for two different kinds of native proteins (pig insulin and hen egg white lysozyme) were done by the extended negative factor counting method in which the matrix elements have been calculated at the ab initio level with the help of a minimal basis and the simulation of the aqueous solution environment. The hopping conductivities were worked out by the formulas of the random walk theory of Lax and co‐workers. The electronic density of states of these native proteins confirmed the conclusions obtained previously from aperiodic model peptides chains. The results show that the ac conductivity vs. frequency curve of these native proteins lies in the range of some typical good inorganic amorphous conductors and thus confirm that proteins, if doped, are amorphous conductors. The behavior of the ac conductivities of the proteins in different ranges of frequencies are discussed. © 1994 John Wiley & Sons, Inc.
One‐electron properties of molecules calculated using second‐order multireference perturbation theory
Authors: Kozlowski P. M. , Davidson E. R. 
Published: January 2005

AbstractA new form of second‐order multireference perturbation theory coupled with finite‐field perturbation theory is applied to evaluate some one‐electron molecular properties. Several possible definitions of the zeroth‐order Hamiltonian are considered and results tested against bench‐mark full CI calculations. © 1995 John Wiley & Sons, Inc.
A BCS approach to molecular correlation
Authors: Piris M. , Cruz R. 
Published: January 2005

AbstractA new method is proposed for calculating the ground‐state energy and the corresponding electronic correlation energy of molecules with an even number of electrons. A transformation of single‐electron terms of the Hamiltonian into terms of the double‐electron type and the application of the Hartree–Fock–Bogolyubov variational principle to the new equivalent Hamiltonian are presented. A Bardeen–Cooper–Schrieffer‐type ansatz is used for the molecular wave function in analogy with the description of superconductivity in metals. Some test calculations on the ground state of several molecules show the goodness of this method. © 1995 John Wiley & Sons, Inc.
Structural analysis of certain linear operators representing chemical network systems via the existence and uniqueness theorems of spectral resolution. II
Authors: Arimoto Shigeru , Fukui Kenichi , Taylor Keith F. , Mezey Paul G. 
Published: January 2005

AbstractThe methodology and theoretical framework of Part I of this series of articles have been further developed to the setting of the Banach algebra B(ℬ︁), of all bounded operators acting on a Banach space ℬ︁. Using the above setting B(ℬ︁), certain dynamical systems of chemical kinetic equations are illustrated in conjunction with Part I and with the analysis of more general systems, some of which will be made in Part III of this series of articles. The main theorem and its auxiliary theorem in the present article elucidate in a unifying manner the structure and the underlying pattern of the spectral symmetry of linear operators (acting on Banach spaces and Hilbert spaces) that are investigated in each of the research fields of dynamical systems and quantum chemistry involving the spectral symmetry of alternant hydrocarbons. © 1995 John Wiley & Sons, Inc.
Perturbation expansion of the ground‐state energy for the one‐dimensional cyclic Hubbard system in the Hückel limit
Authors: Takahashi M. , Bracken P. , Čížek J. , Paldus J. 
Published: January 2005

AbstractThe perturbation expansion coefficients for the ground‐state energy of the half‐filled one‐dimensional Hubbard model with N = 4ν + 2, (ν = 1, 2,…) sites and satisfying cyclic boundary conditions were calculated in the Hückel limit (U/β → 0), where β designates the one‐electron hopping or resonance integral, and U, the two‐electron on‐site Coulomb integral. This was achieved by solving—order by order—the Lieb–Wu equations, a system of transcendental equations that determines the set of quasi‐momenta {ki} and spin variables {τα} for this model. The exact values for these quantities were found for the N = 6 member ring up to the 20th order in terms of the coupling constant B = U/2β, as well as numerically for 10 ⩽ N ⩽ 50, and the N = 6 Lieb–Wu system was reduced to a system of sextic algebraic equations. These results are compared with those of the infinite system derived analytically by Misurkin and Ovchinnikov [Teor. Mat. Fiz. 11, 127 (1972)]. It is further shown how the results of this article can be used for the interpolation by the root of a polynomial. It is demonstrated that a polynomial of relatively small degree provides a very good approximation for the energy in the intermediate coupling region. © 1995 John Wiley & Sons, Inc.
“Neglect of Diatomic Differential Overlap” in nonempirical quantum chemical orbital theories. I. On the justification of the neglect of diatomic differential overlap approximation
Authors: Neymeyr Klaus , Seelig Friedrich Franz 
Published: January 2005

AbstractA short review of the different approaches to the justification of the Neglect of Diatomic Differential Overlap in the basis of symmetrically orthogonalized basis functions is given. Brown and Roby employed the binomial expansion for the approximation of the inverse square root of the overlap matrix. For some overlap matrices, this expansion does not converge. The always‐convergent power series given by Chandler and Grader provides a worse second‐order approximation in comparison with the second‐order binomial expansion. © 1995 John Wiley & Sons, Inc.
Structure and bonding study of the P2 + P2+ system
Authors: Su Yu‐Nung , Chu San‐Yan 
Published: January 2005

AbstractThe structures of P2 + P2+ were studied with ab initio calculations at the ROHF and UHF levels with the 6‐31G* basis set. The geometries and dissociation energies for the four selected structures–collinear, T‐shaped, regular trapezoid, and elongated tetrahedral–were studied in comparison with N2 + N2+. The trade‐off of the intramolecular π bond for the intermolecular σ bond for the P4+ system results in its larger dissociation energies and more substantial changes in bond distances than those in the N4+ system. © 1995 John Wiley & Sons, Inc.
Transformation between Cartesian and pure spherical harmonic Gaussians
Authors: Schlegel H. Bernhard , Frisch Michael J. 
Published: January 2005

AbstractSpherical Gaussians can be expressed as linear combinations of the appropriate Cartesian Gaussians. General expressions for the transformation coefficients are given. Values for the transformation coefficients are tabulated up to h‐type functions. © 1995 John Wiley & Sons, Inc.
Ground‐state and some excited states of Li2 by the half‐projected Hartree–Fock method
Authors: Fernández‐serra P. , Botella V. , Smeyers Y. G. , Galano A. , Delgado‐Barrio G. 
Published: January 2005

AbstractThe half‐projected Hartree–Fock wave function (HPHF) is one of simplest models for introducing some electronic correlation effects. In this model, the wave function is built up with only two Slater determinants. This simple form suggests its application for the direct determination of singlet excited states. On the other hand, because the HPHF model does not mix singlet and triplet states with Ms = 0, it can be used for determining independently singlet and triplet states without any mutual contamination. In the present work, we applied this model to determine nine electronic states of the lithium molecule; one of them exhibits even the same symmetry of the fundamental one. For this purpose, the 6‐311G(d) basis was used. Potential energy curves were determined and some spectroscopic constants derived. The numerical results were compared with the available experimental data, as well as with other theoretical values. © 1995 John Wiley & Sons, Inc.
Über einige komplexe Silbersalze
Authors: Hellwig Karl 
Published: January 2005

Abstract1. Die Doppelsalze der Silberhalogenverbindungen mit Silbernitrat und mit den Halogenalkalisalzen existieren nicht nur in fester Form, sondern auch in Lösung, wie aus der stattfindenden Siedepunktserniedrigung und der annähernden Gültigkeit des Massenwirkungsgesetzes hervorgeht.2. Bei den Doppelsalzen mit AgNO3 wandert das Halogensilber als Neutralteil eines komplexen Kations bei der Elektrolyse zur Kathode.3. Die Existenz folgender Doppelsalze (in fester Form) wurde bestätigt:

equation image

und neu gefunden das Doppelsalz:

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