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  • 1
    Electronic Resource
    Electronic Resource
    Charge distributions and valency in copper oxide crystals related to superconductivity (1989)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 91 (1989), S. 2983-2992 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We present an overview of the discrete variational method for calculating orbital states of a molecular cluster in the local density approximation. Then we introduce a new method of embedding a finite molecular cluster in a crystal lattice. This new technique of cluster weighting is based on the bulk stoichiometry of the crystal and the Mulliken populations for chemically complete atoms—those atoms that have all their covalently bonded nearest neighboring atoms also in the cluster. We have applied our new approach to calculate linear-combination-of-atomic-orbitals ground states for seven copper oxide crystals and Cu metal. The average net Mulliken charges calculated for Cu atoms in this way are shown to correlate well with the observed energies of the Cu K edge feature in x-ray absorption spectra of these materials. Several of these compounds are important to understanding the high Tc superconductivity of copper oxides.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.456919
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  • 2
    Electronic Resource
    Electronic Resource
    Electronic structure, binding energies, and interaction potentials of transition metal clusters (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 94 (1991), S. 3735-3747 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The linear combination of atomic orbitals discrete variational method is used to investigate the electronic structure and interatomic interactions of small transition metal particles in the local density theory. Binding energy curves to two-, three-, and four-atom clusters of Fe, Ni, and Pt are calculated at different geometries, and some Fe–Ni clusters are also studied. We thus determined effective pairwise potentials, and three- and four-body effects in an energy expansion by fitting to the binding-energy vs distance data. Use of these data in generating effective potentials for molecular dynamics simulations is discussed. Relativistic effects are estimated for the Pt systems.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.459745
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  • 3
    Electronic Resource
    Electronic Resource
    Molecular dynamics study of a two-dimensional system with screened Coulomb interactions (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 85 (1986), S. 2232-2236 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: We have used molecular dynamics to study a two-dimensional system of point particles with screened Coulomb interactions, in a "box'' whose size is allowed to vary. In addition to determining the familiar energy–temperature relations at both constant area and constant pressure, we have obtained pressure–area isotherms, diffusion constants, and pair-correlation functions. The results of our simulation are expected to be relevant to such systems as polar monolayers on the surface of water (Langmuir films) and thin colloidal suspensions. By monitoring the energy–temperature relation and the diffusion constant, we have observed first order solid–liquid transitions with hysteresis under both constant area and constant pressure conditions. However, the discontinuities in the pressure–area isotherms at the transition are almost imperceptible. Other thermodynamic relations such as area vs temperature at constant pressure, and the derivative of pressure vs area, are presented to support the analysis.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.451118
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  • 4
    Electronic Resource
    Electronic Resource
    Charge and spin transfer and optical properties in conducting porphyrin compounds (1991)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 95 (1991), S. 403-417 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Anisotropic materials made from stacked macrocycles have potential applications as organic conductors and nonlinear optical materials. Using self-consistent-field local density theory, we have been exploring the ground and excited state electronic structures of metal substituted tetraazaporphyrins, phthalocyanines, and tetrabenzoporphyrins. The calculated and measured polarized optical absorption peaks are in satisfactory agreement. The theoretical dipole oscillator strengths provide absolute intensities for verification of transition assignments, which are helpful for identifying low-lying states and excitation mechanisms.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.461442
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  • 5
    Electronic Resource
    Electronic Resource
    Density functional study of fcc iron and iron particles in copper : The 40th annual conference on magnetism and magnetic materials (1996)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 79 (1996), S. 6429-6431 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The first-principles spin-polarized discrete variational method in the framework of density functional theory was employed to investigate the electronic and magnetic structure of fcc (γ) Fe and of γ-Fe particles in copper, represented by 62-atom embedded clusters of cubic geometry. The influence of Al substitutional impurities in γ-Fe and in the Fe particle in Cu was also investigated. Magnetic moments and hyperfine fields were obtained. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.361960
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  • 6
    Electronic Resource
    Electronic Resource
    Electronic defect structure in TiO and MnO (1989)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 65 (1989), S. 4815-4817 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: The electronic structure, charge distribution, magnetic moment, and binding energies are studied in transition-metal monoxides using the discrete variational method in the embedded scheme within the local density formalism. Defect structures such as 1:0, 2:1, 4:1, and 7:2 (vacancy:interstitial ratio) were evaluated with respect to the ideal structure. Ti loses its moment in the 4:1 structure as the 3d electrons are depopulated in the process of redistribution. Mn shows the highest magnetic moment as in the atomic case but varies over a range of 2.23–4.96 μB depending upon the defect structure. Our calculations predict greater stability for the 2:1 defect structure in TiO and MnO. The interstitial metal ion tends to be in a trivalent state in accord with experiments.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.343238
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  • 7
    Electronic Resource
    Electronic Resource
    A comparison of the one-dimensional band structures of Ni tetrabenzoporphyrin and phthalocyanine conducting polymers (1986)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 84 (1986), S. 1033-1038 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The one-dimensional band structures of (tetrabenzoporphyrinato) Ni (II) and (phthalocyaninato) Ni (II) were calculated. The reported band structures include the effects of the stacking perturbation and of the overlap between nearest neighbors. The basis functions for the intermolecular integrals were obtained from a discrete variational X-α calculation of the monomeric species. Electron spin resonance (ESR) experiments on conductive columnar stacks of these metallomacrocycles, partially oxidized with iodine, indicate that carrier electrons are primarily localized onto the ligands in the phthalocyanine species, but also involve the metal in the tetrabenzoporphyrin complex. The present calculations suggest that the ESR data results from a band crossing or near degeneracy between the highest occupied (ligand centered) porphyrin molecular orbital, and the lowest occupied (metal centered) molecular orbital. The analogous levels are more separated in energy in the phthalocyanine derivative.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.450586
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