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  • 1
    Electronic Resource
    Electronic Resource
    Current density functional theory for optical spectra: A polarization functional (2001)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 115 (2001), S. 1995-1999 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: In this paper we present a new approach to calculate optical spectra, which for the first time uses a polarization dependent functional within current density functional theory (CDFT), which was proposed by Vignale and Kohn [Phys. Rev. Lett. 77, 2037 (1996)]. This polarization dependent functional includes exchange-correlation (xc) contributions in the effective macroscopic electric field. This functional is used to calculate the optical absorption spectrum of several common semiconductors. We achieved in all cases good agreement with experiment. © 2001 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.1385370
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  • 2
    Electronic Resource
    Electronic Resource
    Exact solutions of regular approximate relativistic wave equations for hydrogen-like atoms (1994)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 101 (1994), S. 1272-1281 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: Apart from relativistic effects originating from high kinetic energy of an electron in a flat potential, which are treated in first order by the Pauli Hamiltonian, there are relativistic effects even for low-energy electrons if they move in a strong Coulomb potential. The latter effects can be accurately treated already in the zeroth order of an expansion of the Foldy–Wouthuysen transformation, if the expansion is carefully chosen to be nondivergent for r→0 even for Coulomb potentials, as shown by Van Lenthe et al. [J. Chem. Phys. 99, 4597 (1993)] (cf. also Heully et al. [J. Phys. B 19, 2799 (1986)] and Chang et al. [Phys. Scr. 34, 394 (1986)]). In the present paper, it is shown that the solutions of the zeroth order of this two-component regular approximate (ZORA) equation for hydrogen-like atoms are simply scaled solutions of the large component of the Dirac wave function for this problem. The eigenvalues are related in a similar way. As a consequence, it is proven that under some restrictions, the ZORA Hamiltonian is bounded from below for Coulomb-like potentials. Also, an exact result for the first order regular approximate Hamiltonian is given. The method can also be used to obtain exact results for regular approximations of scalar relativistic equations, like the Klein–Gordon equation. The balance between relativistic effects originating from the Coulombic singularity in the potential (typically core penetrating s and p valence electrons in atoms and molecules) and from high kinetic energy (important for high-energy electrons in a flat potential and also for core-avoiding high angular momentum (d, f, and g states in atoms) are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.467819
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Improved density functional theory results for frequency-dependent polarizabilities, by the use of an exchange-correlation potential with correct asymptotic behavior (1996)
    College Park, Md. : American Institute of Physics (AIP)
    The Journal of Chemical Physics 105 (1996), S. 3142-3151 
    Details
    ISSN: 1089-7690
    Source: AIP Digital Archive
    Topics: Physics , Chemistry and Pharmacology
    Notes: The exchange-correlation potentials vxc which are currently fashionable in density functional theory (DFT), such as those obtained from the local density approximation (LDA) or generalized gradient approximations (GGAs), all suffer from incorrect asymptotic behavior. In atomic calculations, this leads to substantial overestimations of both the static polarizability and the frequency dependence of this property. In the present paper, it is shown that the errors in atomic static dipole and quadrupole polarizabilities are reduced by almost an order of magnitude, if a recently proposed model potential with correct Coulombic long-range behavior is used. The frequency dependence is improved similarly. The model potential also removes the overestimation in molecular polarizabilities, leading to slight improvements for average molecular polarizabilities and their frequency dependence. For the polarizability anisotropy we find that the model potential results do not improve over the LDA and GGA results. Our method for calculating frequency-dependent molecular response properties within time-dependent DFT, which we described in more detail elsewhere, is summarized. © 1996 American Institute of Physics.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.472182
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  • 4
    Electronic Resource
    Electronic Resource
    Spatial modulation of the magnetic moment in Co/Pd superlattices observed by polarized neutron reflectivity : 38th Annual Conference on Magnetism and Magnetic Materials (1994)
    [S.l.] : American Institute of Physics (AIP)
    Journal of Applied Physics 75 (1994), S. 6498-6500 
    Details
    ISSN: 1089-7550
    Source: AIP Digital Archive
    Topics: Physics
    Notes: We have measured the specular reflectivity of spin-polarized neutrons from two (111) superlattices, [Pd 80 A(ring)||Co 60 A(ring)]×20/Pd 300 A(ring)/Co 10 A(ring)/GaAs and [Pd 53 A(ring)||Co 32 A(ring)]×10/Pd 30 A(ring)/Cu 354 A(ring)/Si, grown by molecular-beam epitaxy. In a saturating field of 2300 Oe, we extract for the first superlattice a Co moment value of corresponding to 78% of the bulk Co moment. At temperatures ranging from 38 to 295 K, no excess magnetic moment from polarization of the Pd atoms is evident in the nominal Pd layer. Comparable reflectivity data from the second sample support these conclusions.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1063/1.356949
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  • 5
    Electronic Resource
    Electronic Resource
    Relativistic regular two-component Hamiltonians (1996)
    New York, NY : Wiley-Blackwell
    International Journal of Quantum Chemistry 57 (1996), S. 281-293 
    Details
    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: It is shown how the regularized two-component relativistic Hamiltonians of Heully et al. and Chang, Pelissier, and Durand can be viewed as arising from a perturbation expansion that unlike the Pauli expansion remains regular even for singular attractive Coulomb potentials. The performance of these approximate Hamiltonians is tested in the framework of the local density approximation and the relation of their spectrum to that of the Dirac Hamiltonian is discussed. The circumstances under which the current approximations are superior to the Pauli Hamiltonian are analyzed. Finally, it shown how the Hamiltonians could be used within the context of conventional Hartree-Fock theory. © 1996 John Wiley & Sons, Inc.
    Additional Material: 5 Ill.
    Type of Medium: Electronic Resource
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    Paper (German National Licenses)
  • 6
    Electronic Resource
    Electronic Resource
    Thermische Untersuchung einiger Systeme. I. Alkalihalogenid-Aluminiumhalogenid (1967)
    Weinheim : Wiley-Blackwell
    Zeitschrift für anorganische Chemie 353 (1967), S. 93-102 
    Details
    ISSN: 0044-2313
    Keywords: Chemistry ; Inorganic Chemistry
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology
    Description / Table of Contents: The systems RbCl—AlCl3, CsCl—AlCl3, LiI—AlI3, RbI—AlI3, CsI—AlI3 and NH4I—AlI3 have been subjected to a thermal examination. Besides 1:1 compounds in each case, NaAl2I7 and NaAl3I10 were also found. Contrary to calculations by KRIAGOVA the theoretical inference is that, in the alkali-aluminium halides, aluminium will have a tetrahedralsurrounding. Only in fluoride complexes also an octahedral surrounding is possible.
    Notes: Die Systeme RbCl—AlCl3, CsCl—AlCl3, LiJ—AlJ3, RbJ—AlJ3, CsJ—AlJ3 und NH4J—AlJ3 wurden thermisch untersucht. Außer allen 1:1-Verbindungen wurden noch NaAl2J7 und NaAl3J10 gefunden. Im Gegensatz zu den Berechnungen von KRIAGOVA ließ sich theoretisch folgern, daß in den Alkalialuminiumhalogeniden das Aluminium eine tetraedrische Umgebung hat; nur in den Fluoridkomplexen ist auch eine oktaedrische Umgebung möglich.
    Additional Material: 6 Ill.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/zaac.19673530113
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