α-γ transition in Ce. II. A detailed analysis of the Kondo volume-collapse model

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Abstract
The Kondo volume-collapse (KVC) model of the α-γ transition in Ce metal is examined quantitatively using Anderson impurity Hamiltonian parameters obtained from electron spectroscopy. After the hybridization from spectroscopy is scaled by 1.12 to reproduce exactly the experimental zero-temperature susceptibility, the calculation, with no further adjustable parameters, predicts a phase boundary in good agreement with experiment. It is found that the cohesive energy contribution from the hybridization of unoccupied f states and conduction states is quantitatively important in Ce, with a value much larger than the Kondo energy. This contribution is equally large and important for La and Pr, for which the hybridization is often ignored. It is, however, almost spin independent, so that it does not contribute directly to the Kondo energy. Thus the 4f cohesive energy contribution is large in both the α and γ phases, while only the Kondo spin fluctuation energy (and entropy) causes the α-γ transition. This distinguishes the KVC model from the Mott transition model. The Anderson-Hamiltonian-based KVC model is also distinguished from the Kondo-Hamiltonian-based spin-only version of the KVC model in that the latter approach cannot make direct contact with spectroscopic data because charge degrees of freedom are ignored from the outset. This work provides a quantitative confirmation that a unified understanding of the high-energy spectroscopic and low-energy thermodynamic properties of Ce metal has been achieved at the quantitative level.

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