Eur. Phys. J. B 9, 619-634 (1999)
https://doi.org/10.1007/s100510050806

Quantum charge density fluctuations and the y^-a phase transition in Ce^*

¹ Department of Physics, University of Antwerp, UIA, 2610 Antwerpen, Belgium
² Institute of Physical Chemistry of RAS, Leninskii prospect 31, Moscow, 117915, Russia

Corresponding author: ^a alex@uia.ua.ac.be

Received: 19 October 1998
Published online: 15 June 1999

Abstract

We have calculated the quantum quadrupolar interaction due to charge density fluctuations of localized 4f-electrons in Ce by taking into account the angular dependence, the degeneracy of the localized 4orbitals and the spin-orbit coupling. The calculated crystal field of 4f electronic states is in good agreement with neutron diffraction measurements. We show that orientational ordering of quantum quadrupoles drives a phase transition at K which we assign with the transformation. In the phase the centers of mass of the Ce atoms still form a face centered cubic lattice. The theory accounts for the first order character of the transition and for the cubic lattice contraction which accompanies the transition. The transition temperature increases linearly with pressure. Our approach does not involve Kondo spin fluctuations as the significant process for the phase transition.