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Wave Function (wave + function)
Kinds of Wave Function Selected AbstractsWave functions derived from experiment.JOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 4 2003Abstract The constrained Hartree,Fock method using experimental X-ray diffraction data is extended and applied to the case of noncentrosymmetric molecular crystals. A new way to estimate the errors in derived properties as a derivative with respect to added Gaussian noise is also described. Three molecular crystals are examined: ammonia [NH3], urea [CO(NH2)2], and alloxan [(CO)4(NH)2]. The energetic and electrical properties of these molecules in the crystalline state are presented. In all cases, an enhancement of the dipole moment is observed upon application of the experimental constraint. It is found that the phases of the structure factors are robustly determined by the constrained Hartree,Fock model, even in the presence of simulated noise. Plots of the electron density, electrostatic potential, and the electron localization function for the molecules in the crystal are displayed. In general, relative to the Hartree,Fock model, there is a depletion of charge around hydrogen atoms and lone pair regions, and a build-up of charge within the molecular framework near nuclei, directed along the bonds. The electron localization function plots reveal an increase in the pair density between vicinal hydrogen atoms. © 2003 Wiley Periodicals, Inc. J Comput Chem 24: 470,483, 2003 [source] Prediction of gas-phase 13C nuclear magnetic shielding constants using ONIOM and optimally selected basis functionsCONCEPTS IN MAGNETIC RESONANCE, Issue 6 2008M. Tafazzoli Abstract The wave functions for calculating gas-phase 13C nuclear magnetic shielding constants of 22 molecules have been optimally selected using factorial design as a multivariate technique. GIAO and CSGT methods were used for computation of shielding constants. Different wave functions for different types of carbons were recommended. A wave function as the best level of the theory is proposed for almost similar carbons. ONIOM approach for molecules with different types of carbons is applied. The results of GIAO method using the proposed wave function are in very good agreement with the experimental values. An additional series (21 carbons) were used as test sets and their results confirmed the validity of the approaches. © 2008 Wiley Periodicals, Inc.Concepts Magn Reson Part A 32A: 449,461, 2008. [source] Cover Picture: Fortschritte der Physik 11,12 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 11-12 2009Article first published online: 9 NOV 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 10 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 10 2009Article first published online: 14 SEP 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 9 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 9 2009Article first published online: 21 AUG 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 5,7 / 2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 5-7 2009Article first published online: 27 MAY 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 3,4 /2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 3-4 2009Article first published online: 23 MAR 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Cover Picture: Fortschritte der Physik 1,2 /2009FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 1-2 2009Article first published online: 9 FEB 200 The cover page of 2009 shows high-resolution interference "quantum carpet" patterns for the momentum wave function of an interacting Bose-Einstein condensate (BEC). As time progresses (from back to front), the many-body mean field interaction of the BEC first leads to a broadening of the wave function, but then also to a time-varying interference structure by inducing site-dependent nonlinear phase shifts when the BEC is confined in a spatially periodic potential. Imaging the wave function in momentum space for different times leads to a pattern that one reminds of a carefully woven carpet and is hence termed "quantum carpet". Quantum carpets beautifully demonstrate the surprisingly high matter wave coherence of particle-particle interactions in the zero-temperature limit. [source] Coherent state path integral and super-symmetry for condensates composed of bosonic and fermionic atomsFORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 9-10 2007B. Mieck Abstract A super-symmetric coherent state path integral on the Keldysh time contour is considered for bosonic and fermionic atoms which interact among each other with a common short-ranged two-body potential. We investigate the symmetries of Bose-Einstein condensation for the equivalent bosonic and fermionic constituents with the same interaction potential so that a super-symmetry results between the bosonic and fermionic components of super-fields. Apart from the super-unitary invariance U(L | S) of the density terms, we specialize on the examination of super-symmetries for pair condensate terms. Effective equations are derived for anomalous terms which are related to the molecular- and BCS- condensate pairs. A Hubbard-Stratonovich transformation from ,Nambu'-doubled super-fields leads to a generating function with super-matrices for the self-energy whose manifold is given by the orthosympletic super-group Osp(S,S | 2L). A nonlinear sigma model follows from the spontaneous breaking of the ortho-symplectic super-group Osp(S,S | 2L) to the coset decomposition Osp(S,S | 2L) \ U(L | S), U(L | S). The invariant subgroup U(L | S) for the vacuum or background fields is represented by the density terms in the self-energy whereas the super-matrices on the coset space Osp(S,S | 2L) \ U(L | S) describe the anomalous molecular and BCS- pair condensate terms. A change of integration measure is performed for the coset decomposition Osp(S,S | 2L) \ U(L | S) , U(L | S), including a separation of density and anomalous parts of the self-energy with a gradient expansion for the Goldstone modes. The independent anomalous fields in the actions can be transformed by the inverse square root of the metric tensor of Osp(S,S | 2L) \ U(L | S) so that the non-Euclidean integration measure with super-Jacobi-determinant can be removed from the coherent state path integral and Gaussian-like integrations remain. The variations of the independent coset fields in the effective actions result in classical field equations for a nonlinear sigma model with the anomalous terms. The dynamics of the eigenvalues of the coset matrices is determined by Sine-Gordon equations which have a similar meaning for the dynamics of the molecular- and BCS-pair condensates as the Gross-Pitaevskii equation for the coherent wave function in BEC phenomena. [source] A probabilistic approach to quantum mechanics based on ,tomograms'FORTSCHRITTE DER PHYSIK/PROGRESS OF PHYSICS, Issue 7 2006M. Caponigro It is usually believed that a picture of Quantum Mechanics in terms of true probabilities cannot be given due to the uncertainty relations. Here we discuss a tomographic approach to quantum states that leads to a probability representation of quantum states. This can be regarded as a classical-like formulation of quantum mechanics which avoids the counterintuitive concepts of wave function and density operator. The relevant concepts of quantum mechanics are then reconsidered and the epistemological implications of such approach discussed. [source] An accurate few-parameter ground state wave function for the lithium atomINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 13 2009Nicolais L. Guevara Abstract A simple, seven-parameter trial function is proposed for a description of the ground state of the Lithium atom. It includes both spin functions. Inter-electronic distances appear in exponential form as well as in a pre-exponential factor, and the necessary energy matrix elements are evaluated by numerical integration in the space of the relative coordinates. Encouragingly accurate values of the energy and the cusp parameters as well as for some expectation values are obtained. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] Inequivalent electron densities derived from an approximate correlated ground-state wave function using the Hiller,Sucher,Feinberg identity: Comparisons with quantum Monte Carlo densities for He and Ne atomsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2009Claudio Amovilli Abstract The Hiller,Sucher,Feinberg (HSF) identity is combined with the three-parameter correlated wave function of Chandrasekhar in order to generate an alternative electron density ,(r) for the He atom. This and the conventional "local" operator form of ,(r) are then compared with a diffusion quantum Monte Carlo density. An exact limiting relation is also presented, via HSF identity, between the one-particle density matrix and the pair density in a many-electron atom, which transcends its Hartree,Fock counterpart and has no N -representability difficulties. For the Ne atom, the accuracy of the semiempirical correlated electron density recently obtained by Cordero et al. (Phys. Rev. A 2007, 75, 052502) using fine-tuning of Hartree,Fock theory was assessed by appealing to the ground-state density from diffusion quantum Monte Carlo. The high accuracy of the Cordero et al. density was thereby confirmed. A HSF calculation on neon, with a correlated many-body wave function as starting point, is a worthwhile future aim. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2009 [source] New perspectives on the fundamental theorem of density functional theoryINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2008Xiao-Yin Pan Abstract The fundamental theorem of time-independent/time-dependent density functional theory due to Hohenberg,Kohn (HK)/Runge,Gross (RG) proves the bijectivity between the density ,(r)/,(rt) and the Hamiltonian /(t) to within a constant C/function C(t), and wave function ,/, (t). The theorems are each proved for scalar external potential energy operators. By a unitary or equivalently a gauge transformation that preserves the density, we generalize the realm of validity of each theorem to Hamiltonians, which additionally include the momentum operator and a curl-free vector potential energy operator defined in terms of a gauge function , (R)/, (Rt). The original HK/RG theorems then each constitute a special case of this generalization. Thereby, a fourfold hierarchy of such theorems is established. As a consequence of the generalization, the wave function ,/, (t) is shown to be a functional of both the density ,(r)/,(rt), which is a gauge-invariant property, and a gauge function ,(R)/,(Rt). The functional dependence on the gauge function ensures that as required by quantum mechanics, the wave function written as a functional is gauge variant. The hierarchy and the dependence of the wave function functional on the gauge function thus enhance the significance of the phase factor in density functional theory in a manner similar to that of quantum mechanics. Various additional perspectives on the theorem are arrived at. These understandings also address past critiques of time-dependent theory. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Coupled-cluster corrected MR-CISD method with noniterative evaluation of connected triples,INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 12 2008Leszek Meissner Abstract The single-reference coupled-cluster (CC) analysis of the multi-reference configuration interaction singles and doubles (MR-CISD) wave function shows how the MR-CISD results can be used to mimic more effective exponential cluster expansion. The CC corrections have been constructed relying on this analysis and used to improve the accuracy of the MR-CISD energy and reduce the inextensivity error of the MR-CISD method. Disconnected contributions that approximate those components which are not present in the MR-CISD wave function generate the correction terms. Although the linear CI expansion is usually improved through the inclusion of disconnected contributions the coupled-cluster methodology introduces a variety of corrections that, contrary to the CI case, account for higher excitation rank connected components. In this article, we present a combination of both approaches and illustrate its performance on some numerical examples. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Coherent superposition of resonance wave function in terms of weighted orthogonalized natural localized configurationsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2008A. H. Pakiari Abstract In this research, the projection technique has been applied in order to decompose the electronic wave function into its weighted orthogonalized resonance components. These components have been constructed by determinants whose orbitals are selected among natural bond orbitals. However, the procedure is general and any other localized orbitals can be used as well. Both , and , delocalize systems have been considered in order to check the reliability of the calculated resonance weights. For ,-systems, the presented procedure could predict significant decrease of weight of certain resonance structures when the molecular planarity was destroyed. Water cyclic clusters were also tested and the results confirmed the existence of strong ,-delocalization in the clusters. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 [source] Nonlinear wave function expansions: A progress reportINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 15 2007Ron Shepard Abstract Some recent progress is reported for a novel nonlinear expansion form for electronic wave functions. This expansion form is based on spin eigenfunctions using the Graphical Unitary Group Approach and the wave function is expanded in a basis of product functions, allowing application to closed and open shell systems and to ground and excited electronic states. Each product basis function is itself a multiconfigurational expansion that depends on a relatively small number of nonlinear parameters called arc factors. Efficient recursive procedures for the computation of reduced one- and two-particle density matrices, overlap matrix elements, and Hamiltonian matrix elements result in a very efficient computational procedure that is applicable to very large configuration state function (CSF) expansions. A new energy-based optimization approach is presented based on product function splitting and variational recombination. Convergence of both valence correlation energy and dynamical correlation energy with respect to the product function basis dimension is examined. A wave function analysis approach suitable for very large CSF expansions is presented based on Shavitt graph node density and arc density. Some new closed-form expressions for various Shavitt Graph and Auxiliary Pair Graph statistics are presented. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] The N -particle wave function as a homogeneous functional of the densityINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2007Tamás Gál Abstract It is shown that requiring consistency with the structure of the equation that determines the wave function associated to a density ,() by density-functional theory, yields the N -particle wave function as a degree-half homogeneous functional of the density, and leads to a separation A[N, ,] of N dependence (with N = ,,() d) of density functionals A[,] = A[,,, ,] for which A[,,, ,,] = , A[,, ,]; as a consequence of the linearity of quantum mechanical operators. This implies that the ground-state value of any quantum mechanical observable arises naturally as a degree-one homogeneous N -particle density functional. This general scheme for the structure of density functionals can be considered as the conceptual generalization of the Weizsäcker functional, which is the exact degree-one homogeneous one-particle kinetic-energy density functional. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Non,Born,Oppenheimer calculations of the ground state of H3INTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 14 2007Mauricio Cafiero Abstract We present quantum,mechanical calculations for the ground state of the H3 system performed without the Born-Oppenehimer approximation. In the calculations we use explicitly correlated Gaussian basis functions that explicitly depend on all of the interparticle distances. These basis functions allow us to achieve high accuracy while explicitly describing nucleus,nucleus, nucleus,electron, and electron,electron correlation effects. Gaussian basis sets ranging in size from 85 to 950 functions have been optimized using a gradient-based procedure. The issue of defining and extracting the H3 molecular structure based on the non-BO wave function is also discussed. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Differentiability of Lieb functional in electronic density functional theoryINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 10 2007Paul E. Lammert Abstract A solid understanding of the Lieb functional FL is important because of its centrality in the foundations of electronic density functional theory. A basic question is whether directional derivatives of FL at an ensemble-V-representable density are given by (minus) the potential. A widely accepted purported proof that FL is Gâteaux differentiable at EV-representable densities would say, "yes." But that proof is fallacious, as shown here. FL is not Gâteaux differentiable in the normal sense, nor is it continuous. By means of a constructive approach, however, we are able to show that the derivative of FL at an EV-representable density ,0 in the direction of ,1 is given by the potential if ,0 and ,1 are everywhere strictly greater than zero, and they and the ground state wave function have square integrable derivatives through second order. © 2007 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Bound D-states of helium atom under Debye screeningINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 2 2007Sabyasachi Kar Abstract We have investigated the 1snd1,3D (3 , n , 7) state energies of helium atom embedded in weakly coupled plasma environments using the Rayleigh,Ritz variational method. The effect of the plasma environment is taken care of using a Debye screening model. A correlated wave function involving exponential expansion has been used to represent correlation between the charge particles. The bound 1snd1,3D (3 , n , 7) state energies of helium for various Debye lengths along with the excitation energies of few singlet and triplet states are reported. Our results are useful references to atomic physics, plasma physics, and astrophysics research communities. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2007 [source] Role of the one-body Jastrow factor in the transcorrelated self-consistent field equationINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 7 2006Naoto Umezawa Abstract The one-body Jastrow factor has been introduced into the transcorrelated variational Monte Carlo (TC-VMC) method. The principal role of the one-body Jastrow factor in the Jastrow,Slater-type wave function is to prevent an unfavorable effect of the two-body Jastrow factor that alters the charge density. In the TC-VMC method, since the one-body orbitals are optimized by the transcorrelated self-consistent field (TC-SCF) equations, which take into account the electron,electron correlation interactions originating from the two-body Jastrow factor, the unfavorable effect of altering charge density can be avoided without introducing the one-body Jastrow factor. However, it is found that it is still better to incorporate a one-body Jastrow factor into the TC-VMC method for the practical effect of reducing numerical errors caused by the Monte Carlo sampling and the re-weighting calculations in solving the TC-SCF equations. Moreover, since the one-body Jastrow function adopted in the present work is constructed from the two-body Jastrow factor without increasing any variational parameter, the computational cost is not significantly increased. The preferable effect of the use of the one-body Jastrow factor in the TC-VMC calculation is demonstrated for atoms. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 [source] Exponentially accurate quasimodes for the time-independent Born,Oppenheimer approximation on a one-dimensional molecular systemINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005George A. Hagedorn Abstract We consider the eigenvalue problem for a one-dimensional molecular-type quantum Hamiltonian that has the form where h(y) is an analytic family of self-adjoint operators that has a discrete, nondegenerate electronic level ,(y) for y in some open subset of ,. Near a local minimum of the electronic level ,(y) that is not at a level crossing, we construct quasimodes that are exponentially accurate in the square of the Born,Oppenheimer parameter , by optimal truncation of the Rayleigh,Schrödinger series. That is, we construct an energy E, and a wave function ,,, such that the L2 -norm of ,, is ,,(1) and the L2 -norm of (H(,) , E,),, is bounded by , exp(,,/,2) with , > 0. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Energy decomposition scheme for combined ab initio quantum mechanical / molecular mechanical methodsINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2005Imre Berente Abstract A new energy decomposition scheme is presented which paves the way toward the accurate and simple treatment of boundary atoms in combined ab initio quantum mechanical / molecular mechanical methods. We extend the wave function beyond the quantum region to a few atoms of the molecular mechanical region, which are linked directly to boundary atoms. Furthermore, we apply an approximate decomposition scheme, which allows calculating the total energy in terms of one-center atomic contributions. Comparisons with reference ab initio calculations are made, and good agreement is obtained for geometry parameters referring to CC, CC, and CX (XO, S, N) bonds at the boundary, as well as for the rotational energy curve of n -butane. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Nonadiabatic evolution of electronic states by electron nuclear dynamics theoryINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 5 2005Frank Hagelberg Abstract The problem of how to determine the nonadiabatic content of any given dynamic process involving molecular motion is addressed in the context of Electron Nuclear Dynamics (END) theory. Specifically, it is proposed to cast the dynamic END wave function into the language of static electronic configurations with time dependent complex-valued amplitudes. This is achieved by adiabatic transport of an electronic basis along the classical nuclear trajectories of the studied molecular system, as yielded by END simulation. Projecting the dynamic wave function on this basis yields a natural distinction between adiabatic and nonadiabatic components of the motion considered. Tracing the evolution of the leading configurations is shown to be a helpful device for clarifying the physical nature of electronic excitation processes. For illustration of these concepts, dynamic configuration analysis is applied to the scattering of a proton by a lithium atom. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005 [source] Using 1,3-butadiene and 1,3,5-hexatriene to model the cis-trans isomerization of retinal, the chromophore in the visual pigment rhodopsinINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 4-5 2002Fredrik Blomgren Abstract The short polyenes 1,3-butadiene and 1,3,5-hexatriene are used to model the cis-trans isomerization of the protonated Schiff base of retinal (PSBR) in rhodopsin (Rh). We employed the complete active space self-consistent field (CASSCF) method for calculation of the potential energy surfaces (PESs) in C2 symmetry. In the calculations, the central bond was twisted from 0 to 180° in the first singly excited singlet state (Sse), i.e., the state dominated by a configuration with one electron excited from HOMO to LUMO. It was found that the PES of 1,3-butadiene has a maximum whereas the PES of 1,3,5-hexatriene has a minimum for a twist angle of 90°. This is explained by a shift in border of single and double bonds in the Sse state. The first step in the cis-trans isomerization of PSBR, which is the formation of the C6C7 (see Scheme 1 for numbering) twisted PSBR in the first excited singlet state (S1), inside the protein binding pocket of the visual pigment Rh is modeled using crystal coordinates and the calculations performed on 1,3-butadiene and 1,3,5-hexatriene. More specifically, a plausible approximate structure is calculated in a geometric way for the C6C7 90° twisted PSBR, which fits into the protein binding pocket in the best possible way. It has been shown earlier that PSBR has an energy minimum for this angle in S1. The CASSCF method was used to investigate the wave function of the calculated structure of PSBR. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 [source] Calculation of quasiparticle energy of molecular systems by the GW methodINTERNATIONAL JOURNAL OF QUANTUM CHEMISTRY, Issue 3 2001Y. Ohta Abstract The quasiparticle energy of the H2 molecule is calculated by using the GW method, in which the self-energy operator fully depends on the frequency. The initial Green function G0 is constructed from the wave function obtained by the Hartree,Fock approximation (HFA) and local density approximation (LDA) in the framework of the density functional theory (DFT). From the results obtained we have shown that the wave function from the DFT,LDA is more effective than that from the HFA for G0. © 2001 John Wiley & Sons, Inc. Int J Quantum Chem 84: 348,353, 2001 [source] Femtosecond dynamics of electron transfer, localization, and solvation processes at the ice,metal interfaceISRAEL JOURNAL OF CHEMISTRY, Issue 1-2 2005Uwe Bovensiepen The ultrafast dynamics of excess electrons in amorphous ice layers on single-crystal metal surfaces are investigated by femtosecond time- and angle-resolved two-photon-photoemission spectroscopy. Photoexcited electrons are injected from the metal substrate into delocalized states of the conduction band of ice and localize in the ice layer within 100 fs. Subsequently, energetic stabilization of this localized species is observed on a time scale of ,1 ps, which is attributed to electron solvation by nonadiabatic coupling to nuclear degrees of freedom of the surrounding polar molecular environment. Concomitant with this stabilization process, residual wave function overlap of the solvated electron with the metal substrate results in back-transfer by tunneling through the solvation shell. At such interfaces the correlation of electronic and molecular structure with the resulting solvation dynamics can be explored using different substrates as a template. Here we compare data on molecularly thin D2O ice layers grown on Cu(111) and Ru(001). On Ru(001) both the stabilization and back-transfer proceed about three times faster compared to Cu(111), which is attributed to different interfacial structures and the role of d-states, and projected band gaps in the electron transfer process. [source] Structural, electronic, and optical properties of 9-heterofluorenes: A quantum chemical studyJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 13 2007Run-Feng Chen Abstract Density-functional theory studies were applied to investigate the structural, electronic, and optical properties of 9-heterofluorenes achieved by substituting the carbon at 9 position of fluorene with silicon, germanium, nitrogen, phosphor, oxygen, sulfur, selenium, or boron. These heterofluorenes and their oligomers up to pentamers are highly aromatic and electrooptically active. The alkyl and aryl substituents of the heteroatom have limited influence, but the oxidation of the atom has significant influence on their molecular structures and properties. The highest occupied molecular orbital (HOMO)-lowest occupied molecular orbital (LUMO) interaction theory was successfully applied to analyze the energy levels and the frontier wave functions of these heterofluorenes. Most heterofluorenes belong to type B of interaction with low-lying LUMO and have the second kind of wave function. Carbazole and selenafluorene have type C of interaction with high-lying HOMO and the third kind of wave function. Types C and D of heterofluorenes, such as carbazole, oxygafluorene, sulfurafluorene, and selenafluorene also have high triplet state energies. The extrapolated HOMO and LUMO for polyheterofluorenes indicate that polyselenonafluorene has the lowest LUMO; polycarbazole has the highest HOMO; polyselenafluorene has the highest bandgap (Eg); and polyborafluorene has the lowest Eg. Heterofluorenes and their oligomers and polymers are of great experimental interests, especially those having extraordinary properties revealed in this study. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] A combined electronegativity equalization and electrostatic potential fit method for the determination of atomic point chargesJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 12 2007Imre Berente Abstract We report an approach for the determination of atomic monopoles of macromolecular systems using connectivity and geometry parameters alone. The method is appropriate also for the calculation of charge distributions based on the quantum mechanically determined wave function and does not suffer from the mathematical instability of other electrostatic potential fit methods. © 2007 Wiley Periodicals, Inc. J Comput Chem, 2007 [source] Electron correlation: The many-body problem at the heart of chemistryJOURNAL OF COMPUTATIONAL CHEMISTRY, Issue 8 2007David P. Tew Abstract The physical interactions among electrons and nuclei, responsible for the chemistry of atoms and molecules, is well described by quantum mechanics and chemistry is therefore fully described by the solutions of the Schrödinger equation. In all but the simplest systems we must be content with approximate solutions, the principal difficulty being the treatment of the correlation between the motions of the many electrons, arising from their mutual repulsion. This article aims to provide a clear understanding of the physical concept of electron correlation and the modern methods used for its approximation. Using helium as a simple case study and beginning with an uncorrelated orbital picture of electronic motion, we first introduce Fermi correlation, arising from the symmetry requirements of the exact wave function, and then consider the Coulomb correlation arising from the mutual Coulomb repulsion between the electrons. Finally, we briefly discuss the general treatment of electron correlation in modern electronic-structure theory, focussing on the Hartree-Fock and coupled-cluster methods and addressing static and dynamical Coulomb correlation. © 2007 Wiley Periodicals, Inc. J Comput Chem 28: 1307,1320, 2007 [source] | ||||||||||||||||||||||