Electronic structure and oxidation states in high-pressure synthesized isostructural CeCN$_5$ and TbCN$_5$
Abstract
Understanding the behavior of 4 electrons in materials containing rare earth elements is one of the fundamental questions within condensed matter physics. In this work the electronic properties of isostructural CeCN and TbCN, both recently synthesized at extreme pressure, are investigated using Density Functional Theory (DFT) calculations. We include the on-site Coulomb repulsion between localized 4 states within the static DFT+U framework; the DFT+U results are cross-checked with DFT+dynamical mean-field theory (DMFT) calculations within the quasi-atomic (Hubbard-I) approximation. Despite CeCN and TbCN being isostructural compounds Ce and Tb show different oxidation states, 4+ and 3+ respectively. This leads to distinctly different electronic properties: the former compound is an insulator, while the latter is a metal. An extra electron which is donated by Ce to the polymeric C-N network is distributed across the network. This leads to a modification of the bond length in CeCN compared to TbCN. Still, the polymeric C-N networks can accommodate the different oxidation states in isostructural lanthanide-carbon-nitrogen (LnCN) compounds. Our results underline that LnCN compounds under high pressure offer a unique platform for probing the interplay between 4-electron behavior and structural complexity.
Keywords
Cite
@article{arxiv.2604.19629,
title = {Electronic structure and oxidation states in high-pressure synthesized isostructural CeCN$_5$ and TbCN$_5$},
author = {Amanda Ehn and Florian Trybel and Talha Bin Masood and Leonid V. Pourovskii and Igor A. Abrikosov},
journal= {arXiv preprint arXiv:2604.19629},
year = {2026}
}