Electronic Correlation Strength of Inorganic Electrides from First Principles

Strongly correlated electron systems, generally recognized as d- and f-electron systems, have attracted attention as a platform for the emergence of exotic properties such as high-Tc superconductivity. However, correlated electron behaviors have been recently observed in a group of novel materials, electrides, in which s-electrons are confined in subnanometer-sized spaces. Here, we present a trend of electronic correlation of electrides by evaluating the electronic correlation strength obtained from model parameters characterizing effective Hamiltonians of 19 electrides from first principles. The calculated strengths vary in the order 0D ≫ 1D > 2D ∼ 3D electrides, which corresponds to experimental trends, and exceed 10 (a measure for the emergence of exotic properties) in all of the 0D and some of the 1D electrides. We also found the electronic correlation depends on the cation species surrounding the s-electrons. The results indicate that low-dimensional electrides will be new research targets for studies of strongly correlated electron systems.