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  • 1
    Electronic Resource
    Electronic Resource
    On the pressure-temperature phase diagram of intermediate valence compounds (1978)
    Springer
    The European physical journal 32 (1978), S. 93-97 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The pressure-temperature (P, T) phase diagram of intermediate valence compounds has been calculated on the basis of the periodic Anderson model which was extended to include the interaction of 4f electrons with longitudinal optical phonons. It is shown that the positive slope (dP/dT〉0) of the phase boundary between the insulating and the mixed valence phase as observed experimentally in Sm S and many other systems is determined by the behaviour of the electronic density of states of the interacting system as function ofP. Moreover, the observed anomalous thermal contraction in the insulating phase near the phase boundary and the anomalously large thermal expansion in the metallic phase are well described by numerical results for the extended periodic Anderson model.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322191
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  • 2
    Electronic Resource
    Electronic Resource
    Self-consistent alloy treatment of the periodic anderson model: Susceptibility and specific heat of intermediate valence compounds (1979)
    Springer
    The European physical journal 35 (1979), S. 7-14 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract To describe the electronic properties of mixed valence compounds we study the periodic Anderson model within the frame of the alloy analog approximation. In this approach the model Hamiltonian is replaced by the sum of two single-particle alloy Hamiltonians the parameters of which have to be determined self-consistently. The alloy problem is solved within the coherent potential approximation. In contrast to other treatments of the periodic Anderson model this approximation scheme is exact in both trivially solvable limits of vanishing hybridization and Coulomb repulsion, respectively. For model parameters corresponding to a mixed valence situation only nonmagnetic solutions of the self-consistency equations exist. After discussing the limit of small hybridization analytically we numerically calculate the magnetic susceptibility and the electronic specific heat as a function of temperature for realistic values of the hybridization and Coulomb repulsion. The results are in very good qualitative agreement with experimental data.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01322076
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    Paper (German National Licenses)
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  • 3
    Electronic Resource
    Electronic Resource
    Theory of substitutional alloys of intermediate valence systems: Concentration and temperature dependence of the static magnetic susceptibility (1980)
    Springer
    The European physical journal 38 (1980), S. 219-226 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The effect of alloying in intermediate valence compounds is studied within an extended version of the Anderson model which takes into account substitutional disorder of the rare earth ions. In particular, we concentrate on modifications of the conduction band, describe them by an effective shift in the Fermi energy, and consider its influence on the mixed valence behaviour. By applying the alloy analog approximation to the manyparticle Hamiltonian describing the local magnetic 4f shells, the complete effective Hamiltonian is that of a ternary alloy. This problem is solved within the coherent potential approximation and the static magnetic susceptibility is calculated as a function of temperature and disorder. Depending on the shift of the Fermi energy with respect to the 4f levels, qualitatively different behaviour is obtained which corresponds very well with magnetic measurements on different Yb alloys. The model yields an inverse proportionality between the susceptibility atT=0 and the temperatureT M of the susceptibility maximum as functions of the disorder.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01315660
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  • 4
    Electronic Resource
    Electronic Resource
    Transport properties of intermediate valence compounds studied within the alloy analog approximation of the Periodic Anderson Model (1981)
    Springer
    The European physical journal 44 (1981), S. 59-71 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract We use the Periodic Anderson Model (PAM) to describe the transport properties of intermediate valence compounds. The transport quantities of interest are related to the current-current response function. Therefore, a current operator being consistent with the PAM Hamiltonian must be defined. This aim is achieved by defining a proper particle density operator and using the continuity equation. The PAM is treated within the alloy analog approximation, i.e. it is replaced by the sum of two effective single-particle “alloy”-Hamiltonians, which are treated within the coherent potential approximation (CPA). Then the CPA for transport quantities is used to calculate the current-current response function. It is shown that for all reasonable assumptions for the conduction band and the hybridization dispersion the current vertex corrections vanish within the CPA. For different assumptions concerning the hybridization dispersion, we present numerical results for the temperature and parameter dependence of some transport quantities, in particular the static resistivity. The relevance of these results for the understanding of the typical experimental resistivity behaviour obtained for different intermediate valence compounds and possible shortcomings of our approach are discussed.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01292653
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  • 5
    Electronic Resource
    Electronic Resource
    The spinless periodic Anderson model with phonons and applications to mixed valence systems (1978)
    Springer
    The European physical journal 30 (1978), S. 393-402 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract A simplified periodic Anderson model, without spin and Hubbard correlation, coupled to a branch of optical phonons is presented and discussed in connection with Rare Earth compounds exhibiting a transition to a mixed valence state. The phonon self energy is approximately calculated by diagrammatic techniques and used for a study of boson modes originating from the interplay of phonons withf-electrons mixed into band states. It is shown that weakly damped low lying or even soft modes may exist in connection with the transition. The relevance of these results to real systems, possible shortcomings of the model and the relations to other work in this field is described.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01321092
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  • 6
    Electronic Resource
    Electronic Resource
    Phonon induced instabilities in intermediate valence compounds (1978)
    Springer
    The European physical journal 30 (1978), S. 277-285 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The coupling of 4f electrons and longitudinal optical phonons and its implications on different types of structural phase transitions in intermediate valence compounds is discussed within the framework of the periodic Anderson model. Two types of interactions are considered. First, the usual density type of coupling of 4f electrons and phonons leads to a weakly temperature dependent renormalization of the positionE 0 of the 4f level with respect to the 5d band. Secondly, phonon induced 4f–5d interband transitions lead to a renormalization of the hybridization energyV of 4f and conduction electrons. For appropriate parameter values the latter effect gives rise to discontinuous changes of the occupation of the 4f state. The tendency towards a ferromagnetic or antiferromagnetic instability is essentially suppressed by the presence of phonons.The dependence of the susceptibility on temperature and onE 0 is calculated and a jump is found whenever a discontinuous change of the occupation of the 4f state occurs.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01320033
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  • 7
    Electronic Resource
    Electronic Resource
    Susceptibility and specific heat of intermediate valence compounds studied in mean-field theory of a periodic anderson model (1978)
    Springer
    The European physical journal 29 (1978), S. 341-347 
    Details
    ISSN: 1434-6036
    Source: Springer Online Journal Archives 1860-2000
    Topics: Physics
    Notes: Abstract The periodic Anderson model for a lattice of magnetic ions is investigated in Hartree-Fock approximation. Attention is paid to different solutions of the self-consistency equations corresponding to ferromagnetic or antiferromagnetic ordering of the local magnetic moments. The effect of hybridization leading to reduced magnetic moments strongly depends on the position of the localizedf levels relative to the conduction band. For paramagnetic solutions with a non-integer value for thef level occupation number comparison is made with properties of intermediate valence rare earth compounds. The mean-field results for the susceptibility and specific heat agree with essential features found for these substances.
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1007/BF01324031
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  • 8
    Electronic Resource
    Electronic Resource
    104. Entmonomerisierung von Polymerisationslatices (1993)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 65 (1993), S. 1116-1116 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3306509106
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  • 9
    Electronic Resource
    Electronic Resource
    184. Aufbereitung monomerbelasteter Abwässer der Kautschukproduktion (1994)
    Weinheim : Wiley-Blackwell
    Chemie Ingenieur Technik - CIT 66 (1994), S. 1271-1271 
    Details
    ISSN: 0009-286X
    Keywords: Chemistry ; Polymer and Materials Science
    Source: Wiley InterScience Backfile Collection 1832-2000
    Topics: Chemistry and Pharmacology , Process Engineering, Biotechnology, Nutrition Technology
    Type of Medium: Electronic Resource
    URL: http://dx.doi.org/10.1002/cite.3306609185
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