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  • 1
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 97 (1992), S. 2578-2582 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Ionization potentials (I) and electron affinities (A) of lithium clusters are studied by treating exchange effects exactly within the exchange-only density-functional theory and employing the spherical jellium background model of metallic clusters. In the past, ionization potentials of metallic clusters have been studied by treating the exchange and correlation effects approximately via the local density approximation (LDA). We show that such a calculation leads to ionization potentials which, when extrapolated to large clusters, do not give the correct work function W for the bulk metal as they should. Furthermore, the LDA does not lead to convergent solutions for cluster anions of all sizes. Thus the electron affinities of these clusters cannot be studied within this approximation. On the other hand, by treating exchange effects exactly, solutions for negative ions can also be obtained. We demonstrate that both the ionization potentials and the electron affinities thus obtained extrapolate to the correct value of the work function for the bulk. Furthermore, I and A on the average vary with the size of the cluster as I=W+0.5/(R+a) and A=W−0.5/(R+a), respectively, where R is the radius of the cluster and "a'' is a microscopic distance.
    Type of Medium: Electronic Resource
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  • 2
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 6055-6056 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: By generalization of a method due to Politzer et al. [J. Chem. Phys. 79, 3859 (1983)], it is demonstrated how the absolute hardness of an electronic system can be determined from the electrostatic potential, as a function of position of the system and its positive and negative ions. It is shown that to good accuracy the hardness is one-half the electrostatic potential at the covalent radius due to the Fukui function.
    Type of Medium: Electronic Resource
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  • 3
    Electronic Resource
    Electronic Resource
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 113 (2000), S. 5614-5623 
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Performing electronic structure calculations for large systems, such as nanoparticles or metal clusters, via orbital based Hartree–Fock or Kohn–Sham theories is computationally demanding. To study such systems, therefore, we have taken recourse to the hydrodynamic approach to time-dependent density-functional theory. In this paper we develop a variation-perturbation method within this theory in terms of the particle and current densities of a system. We then apply this to study the linear and nonlinear response properties of alkali metal clusters within the spherical jellium background model. © 2000 American Institute of Physics.
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  • 4
    ISSN: 1434-6079
    Keywords: PACS. 31.25.-v Electron correlation calculations for atoms and molecules-31.90.+s Other topics in the theory of the electronic structure of atoms, molecules, and their ions
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract: The impulse Compton Profiles (CPs) J(q) and the expectation values for some inert gas atoms (He-Kr) are computed and compared within the Harbola-Sahni (HS), Hartree-Fock (HF) theories and a Self-Interaction-Corrected (SIC) density functional model. The Compton profiles for excited states of helium atom are also calculated. While the calculated CPs are found to generally agree, they differ slightly from one another for small values of the Compton parameter q and are in good agreement for large q values. The expectation values within the three theories are also found to be comparable. The HS formalism is seen to mimic HF reasonably well in the momentum space, establishing the logical consistency of the former.
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  • 5
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this comment we point out the similarity between the recent work of Aiga et al. [J. Chem. Phys. 111, 2878 (1999)] and our work [Phys. Lett. A 236, 525 (1997)], both developing perturbation methods within time-dependent density-functional theory for calculating frequency-dependent response properties of many-electron systems. © 2000 American Institute of Physics.
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  • 6
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: The local many-body potential of density-functional theory is thus far understood in its mathematical context as the functional derivative of the exchange-correlation energy functional of the density. In recent work we have attempted to provide a physical interpretation for this potential. We interpret it as the work required to move an electron against the electric field of its Fermi-Coulomb hole charge distribution. Implicit in this interpretation is that the potential is path-independent. For symmetric systems this is rigorously the case. For systems where this may not be the case, the potential may be derived from an effective charge distribution given by the divergence of the field, thus ensuring its path independence. Also implicit as a consequence of the total Coulomb hole charge being zero is that the asymptotic structure of the potential is entirely due to the Fermi hole charge distribution, and thus known precisely. The potential lies explicitly within the rubric of density-functional theory in that within the exchange-only approximation it satisfies the exchange energy virial theorem sum rule and all scaling properties that the exact exchange potential must satisfy. The potential does not satisfy the virial theorem sum rule for the correlation energy, and consequently a term proportional to the difference between the interacting and noninteracting system kinetic energies must be added for the sum rule to be satisfied exactly. The formalism differs from density-functional theory in that it is not derived from the variational principle for the energy, thus obviating the requirement of determining functional derivatives, as well as allowing for the study of excited states. The interpretation also leads to insights into the exact Slater exchange potential, and other approximation schemes such as the Xα method, and local density and gradient expansion approximations. The results of application to few-electron atomic and many-electron metallic surface inhomogeneous electronic systems are remarkably accurate when compared with other theoretical calculations and experiment.
    Additional Material: 2 Ill.
    Type of Medium: Electronic Resource
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  • 7
    Electronic Resource
    Electronic Resource
    New York, NY : Wiley-Blackwell
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: In this article we calculate the asymptotic structure of the exchange potential for the Fermi level electron in the vacuum region outside a metal surface, and show it to be the image potential. In this asymptotic region the exchange potential due to the Fermi level electron is equivalent to the optimized potential of exchange-only density-functional theory. Thus, the asymptotic Kohn-Sham effective potential at a metal surface is the image potential, and arises soley due to correlations which result from the Pauli exclusion principle. © 1993 John Wiley & Sons, Inc.
    Additional Material: 1 Ill.
    Type of Medium: Electronic Resource
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  • 8
    ISSN: 0020-7608
    Keywords: Computational Chemistry and Molecular Modeling ; Atomic, Molecular and Optical Physics
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Notes: We recently proposed a variational method for determining static polarizabilities that uses the ground-state density, rather than the orbitals, of the system for calculations. Thus, the method is different from, and numerically easier than, the perturbation theory approach in which changes in each of the single-particle orbitals have to be obtained self-consistently. For neutral atoms and cations, it leads to results that are comparable to the results obtained by the perturbation theory. In this article, we apply this method, employing Hartree-Fock densities, to obtain polarizabilities for negative ions and show that for negative ions also the results are quite accurate. Thus, the method may prove useful in making quick and accurate estimates of the polarizabilities of more complex systems where orbital based self-consistent calculations become quite complicated. © 1994 John Wiley & Sons, Inc.
    Additional Material: 2 Tab.
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