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31.
Dirk Andrae Ralf Brodbeck Juergen Hinze 《International journal of quantum chemistry》2001,82(5):227-241
We studied several exchange‐only and exchange–correlation energy density functionals in numerical, i.e., basis‐set‐free, nonrelativistic Kohn–Sham calculations for closed‐shell 1S states of atoms and atomic ions with N electrons, where 2≤N≤120. Accurate total energies are presented to serve as reference data for algebraic approaches, as do the numerical Hartree–Fock results, which are also provided. Gradient‐corrected exchange‐only functionals considerably improve the total energies obtained from the usual local density approximation, when compared to the Hartree–Fock results. Such an improvement due to gradient corrections is not seen in general for highest orbital energies, neither for exchange‐only results (to be compared with Hartree–Fock results), nor for exchange–correlation results (to be compared with experimental ionization energies). © 2001 John Wiley & Sons, Inc. Int J Quant Chem 82: 227–241, 2001 相似文献
32.
银洲柴胡(Bupleurum ynchownse Shan et Y. Li)系伞形科柴胡属植物,在我国作为柴胡入药,但它的化学成份尚未见报道。我们对其化学成份进行了研究,分得10个已知化合物。 相似文献
33.
We have investigated the consequences of varying the three parameters in Becke's hybrid exchange‐correlation functional, which includes five contributions: Hartree–Fock exchange, local exchange, Becke's gradient exchange correction, local correlation, and some form of gradient correlation correction. Our primary focus was upon obtaining orbital energies with magnitudes that are reasonable approximations to the electronic ionization potentials; however, we also looked at the effects on molecular geometries and atomization enthalpies. A total of 12 parameter combinations was considered for each of three different gradient correlation corrections: the Lee–Yang–Parr, the Perdew‐86, and the Perdew–Wang 91. Five molecules were included in the study: HCN, N2, N2O, F2O, and H2O. For comparison, a Hartree–Fock calculation was also carried out for each of these. The 6‐31+G** basis set was used throughout this work. We found that the ionization potential estimates can be greatly improved (to much better than Hartree–Fock levels) by increasing the Hartree–Fock exchange contribution at the expense of local exchange. In itself, this also introduces major errors in the atomization enthalpies. However, this can be largely or even completely counteracted by reducing or eliminating the role of the gradient exchange correction. © 2000 John Wiley & Sons, Inc. J Comput Chem 21: 227–238, 2000 相似文献
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35.
Zbigniew Romanowski Abraham F. Jalbout 《International journal of quantum chemistry》2008,108(9):1465-1476
Slater‐type orbitals are applied to represent the numerically obtained Kohn–Sham eigenfunction of free atom. The algorithm evaluating the nonlinear expansion coefficients of this approximation is described. Standard iterative solution of Kohn–Sham equation to obtain the nonlinear expansion coefficients is avoided and replaced by the projection method. First, the eigenfunction is obtained in the B‐spline space based on the Galerkin formulation of the finite element method. Then, based on the density functional theory, the conditions are formulated, which leads to the set of nonlinear equations. The proposed algorithm is general and can be applied for any atomic Kohn–Sham eigenfunction. As an examplary application of the proposed algorithm, the set of nonlinear equations is derived for occupied states of N, Al, Ga, and In atoms. The expansion coefficients, obtained for these atoms, are evaluated numerically by Newton procedure and listed in the tables. © 2008 Wiley Periodicals, Inc. Int J Quantum Chem, 2008 相似文献
36.
Zbigniew Romanowski 《International journal of quantum chemistry》2010,110(10):1793-1802
The approximation properties of Lobatto polynomials are analyzed and then applied to approximate the atomic Kohn–Sham eigenfunction. In the first part of this article the approximation algorithm based on the Galerkin finite element method is derived. To obtain the approximation of the function, based on the presented algorithm, the linear set of equations must be solved. The matrix of the equation set is very sparse and its elements can be evaluated analytically. In the second part of this article, the algorithm is applied to evaluate adaptive polynomial approximation of selected Kohn–Sham eigenstates of indium (In) atom. The proposed r‐adaptive algorithm evaluates the minimum number of subintervals needed to represent the eigenfunction with required accuracy. Based on the r‐adaptive algorithm, the approximations of 4d, 5s 5p In eigenfunctions were calculated. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2010 相似文献
37.
Recently, we showed that unoccupied Kohn‐Sham (KS) orbitals stemming from DFT calculations of a neutral system can be used to derive accurate estimates of the free energy and electronic couplings for excess electron transfer in DNA (Félix and Voityuk, J Phys Chem A 2008, 112, 9043). In this article, we consider the propagation of radical cation states (hole transfer) through DNA π‐stacks and compare the performance of different exchange‐correlation functionals to estimate the hole transfer (HT) parameters. Two different approaches are used: (1) calculations that use occupied KS orbitals of neutral π stacks of nucleobases, and (2) the time‐dependent DFT method which is applied to the radical cation states of these stacks. Comparison of the calculated parameters with the reference data suggests that the best results are provided by the KS scheme with hybrid functionals (B3LYP, PBE0, and BH&HLYP). The TD DFT approach gives significantly less accurate values of the HT parameters. In agreement with high‐level ab initio results, the KS scheme predicts that the hole in π stacks is confined to a single nucleobase; in contrast, the spin‐unrestricted DFT method considerably overestimates the hole delocalization in the radical cations. © 2009 Wiley Periodicals, Inc. Int J Quantum Chem, 2011 相似文献
38.
A. I. Kuleff Y. I. Delchev P. Tz. Yotov Tz. Mineva J. Maruani 《International journal of quantum chemistry》2002,89(4):217-226
Strutinsky's standard averaging method is formulated in the framework of the extended Kohn–Sham scheme and a two‐step procedure permitting the application of the method is proposed. A Taylor‐series expansion of the ground‐state energy‐function of the occupation numbers is derived, which involves the averaged energy as the leading term and shell corrections as smaller terms. Numerical applications for atoms and ions from Be through Ar are presented and discussed. © 2002 Wiley Periodicals, Inc. Int J Quantum Chem, 2002 相似文献
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We present the story of full three-dimensional ab initio simulation techniques of dense plasmas based on the Kohn–Sham realization of the density functional theory, starting from early attempts using the Car–Parrinello method to the most recent approaches based on density matrix. We recall the decisive role played by two experiments, one on the Nova laser and the other at a much smaller scale, with pulsed electrical discharges. We emphasize that the essential roles of the Physics of Non-Ideal Plasmas (PNP) and Strongly Coupled Coulomb Systems (SCCS) conference series were most results, and simulation tools were presented and discussed under the benevolent presence of Vladimir Fortov. 相似文献
40.
Under the Kohn–Sham theory, we examine solutions for the equations δTS/δρ(r) = 0 and δTS/δρ(r) = νKS(r) that link the chemical potential of the electronic system with the effective Kohn–Sham potential through μ = νKS(r) + δTS/δρ. For single ions, we identify the chemical potential with the eigenvalue of the frontier orbital when the atom is in the limit of full ionization. For the case of cations, the chemical potential is found above ?(I + A)/2 and has the property of grouping ions with the same chemical characteristics. For the anion instead, the chemical potential is fixed at the ionization energy. By solving the above equations numerically, two radial points called r? and r+ are obtained and compared with the Shannon–Prewitt ionic radius. Moreover, we found for the halide series, that r? is numerically equivalent to rm, the radii where the electrostatic potential has its minimum, but shows different behavior upon charge variation. © 2006 Wiley Periodicals, Inc. Int J Quantum Chem, 2006 相似文献