Quantum charge density fluctuations and the gamma-alpha phase transition in Ceстатья
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Дата последнего поиска статьи во внешних источниках: 18 декабря 2013 г.
Аннотация:We have calculated the quantum quadrupolar interaction due to charge density fluctuations
of localized 4f-electrons in gamma−Ce by taking into account the angular dependence, the degeneracy of the localized 4f−orbitals and the spin-orbit coupling. The calculated crystal eld of 4f electronic states is in good agreement with neutron diraction measurements. We show that orientational ordering of quantum quadrupoles drives a Fm3m - Pa3 phase transition at 86 K which we assign with the gamma − alpha transformation.
In the Pa3 phase the centers of mass of the Ce atoms still form a face centered cubic lattice. The theory accounts for the rst 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 signicant process for the phase transition.