Pressure Induced Valence Transition in Cerium Studied by Positron Annihilation Spectroscopy

  • A. Bharathi
  • K. P. Gopinathan
  • C. S. Sundar
  • B. Viswanathan


The low pressure fcc γ-phase of Ce at ambient temperature is known to possess the properties of a trivalent rare earth metal. On the application of pressure at ~ 8 kbar, it undergoes a first order isostructural transition to the a-phase, accompanied by a decrease in lattice parameter from 5.16 to 4.85 Å. At ~ 55 kbar, Ce transforms to another close packed structure (α’ phase) with a lattice parameter of 4.66 Å. Our earlier understanding of the mechanism of the pressure induced γ → α transition was on the basis of the 4f-promotional model [1]. This assumes that the 4f-level in the γ-phase is well localised and occupied by one electron per atom and that this electron is completely or partially (0.7 electron) transferred to the conduction band in the α-phase. Recent spectroscopic measurements such as photo-emission [2], x-ray absorption [3] and Compton scattering [4] provided evidence against the validity of the 4f-promotional model and raised a controversy on the question of valence in the collapsed phase. The detailed mechanism of the valence transitions and the nature of 4f-delocalisation in the high pressure phases are still not fully understood.


Carbide Tungsten Bismuth Cerium 


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  1. [1]
    D.C. Koskenmaki and K.A. Gschneidner, in “Handbook on the Physics and Chemistry of Rare Earths”, K.A. Gschneidner and L. Eyring eds. (North-Holland, Amsterdam,1978) Vol.1, p.337Google Scholar
  2. [2]
    R.D. Parks, M. Martensson and B. Reihl, in “Valence Instabilities”, P. Wachter and H. Boppart, eds (North-Holland, Amsterdam, 1982) p. 239.Google Scholar
  3. [3]
    A. Platan and S.E. Karlsson, Phys. Rev. B18, 3820 (1978)Google Scholar
  4. [4]
    U. Kornstadt, R. Lasser and B. Lengeler, Phys. Rev. B21, 1898 (1980)Google Scholar
  5. [5]
    K.P. Gopinathan, C.S. Sundar and B. Viswanathan, Solid State Comm. 32, 369 (1979)CrossRefGoogle Scholar
  6. [6]
    D.R. Gustafson, J.D. McNutt and L.O. Roellig, Phys. Rev. 183, 435 (1969)CrossRefGoogle Scholar
  7. [7]
    R.F. Gempel, D.R. Gustafson and J.D. Willenberg, Phys. Rev. B5, 2082 (1972)Google Scholar
  8. [8]
    J.D. McGervey, S.G. Usmar, N. Panigrahi, O.D. McMasters, K.A. Gschneidner and C.Y. Huang, in “Positron Annihilation”, P.G. Coleman, S.C. Sharma and L.M. Diana, eds. (North-Holland, Amsterdam, 1982) p.240Google Scholar
  9. [9]
    P. Kirkegaard, M. Eldrup, O.E. Mogensen and N.J. Pedersen, Comput. Phys. Commun. 23, 307 (1981)CrossRefGoogle Scholar
  10. [10]
    W. Brandt, Appl. Phys. 5, 6 (1974)CrossRefGoogle Scholar
  11. [11]
    M.J. Puska and R.M. Nieminen, J. Phys. F13, 333 (1983)CrossRefGoogle Scholar
  12. [12]
    F. Herman and S. Skilmann, “Atomic Structure Calculations” (Prentice-Hall Inc., Englewood Cliffs, New Jersey, 1963)Google Scholar
  13. [13]
    S. Berko and J.S. Plaskett, Phys. Rev. 112, 1877 (1958)CrossRefGoogle Scholar

Copyright information

© Plenum Press, New York 1987

Authors and Affiliations

  • A. Bharathi
    • 1
  • K. P. Gopinathan
    • 1
  • C. S. Sundar
    • 1
  • B. Viswanathan
    • 1
  1. 1.Indira Gandhi Centre for Atomic ResearchKalpakkamIndia

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