Mott vs Kondo: Influence of Various Density Functional Based Methods on the Ce Isostructural Phase Transition Mechanism

TL;DR

This study evaluates how different density functional theory approaches—GGA, MetaGGA, and Hybrid functionals—predict the gamma to alpha iso-structural transition in Ce under hydrostatic compression at zero Kelvin. By systematically varying exchange-correlation treatment and an on-site f-electron Hubbard term, the authors identify two mechanistic regimes: a Mott-like localization favored by hybrid functionals and high $U_{ff}$, and a Kondo-volume-collapse picture favored by moderate $U_{ff}$ in PBE+$U$ and MetaGGA functionals. The Kondo-like results better reproduce the experimental ordering of phases and equilibrium volumes, suggesting the transition may involve overlapping Mott and Kondo physics rather than a single pure mechanism. The findings offer guidance for selecting cost-effective DFT methods and for generating training data for machine-learning interatomic potentials in Ce and related lanthanides, balancing accuracy and computational expense.

Abstract

The cerium iso-structural phase transition (gamma to alpha) is dominated by f-electron localization changes that results in a magnetic ordering change and a volume collapse. Generally, these physics are difficult to capture with ab initio and first principles methods. However, previous works have shown various methods to be successful in predicting at least some of the physics of the gamma to alpha phase transition. Therefore, here, we perform a broad survey of density functional based methods across three levels of theory and types of functions (GGA, MetaGGA, and Hybrid functionals) and compare the results, focusing on hydrostatic compression across the phase boundary at zero Kelvin. For the methods that best reproduce experimental results, we directly probe the predicted mechanisms and frame the results in the Mott/Kondo debate, assessing how the underlying methods and assumptions of different functionals can assess the physical drivers in the phase transition, providing insight into the governing dynamics of this unique phase transition.

Figures (6)

• Figure 1: The energy in reference to the minimum as a function of lattice parameter for PBE and PBE+U with four values for U.
• Figure 2: Total magnetization as a function of lattice parameter for PBE and PBE+$U_{ff}$ with several values for $U_{ff}$.
• Figure 3: The energy in reference to the minimum as a function of lattice parameter for the MetaGGA functionals.
• Figure 4: The energy in reference to the minimum as a function of lattice parameter for all Hybrid functionals used here.
• Figure 5: The energy in reference to the minimum as a function of lattice parameter for most accurate functionals from each level of theory.