Issue 1, 2024

Unconventional stoichiometric two-dimensional potassium nitrides with anion-driven metallicity and superconductivity

Abstract

The design of compounds with interesting coordination geometries, exotic oxidation states, and intriguing properties is of fundamental interest in physics, chemistry, and materials science. Herein, first-principle swarm-intelligence structure search calculations identify two unconventional stoichiometric KN2 and KN4 monolayers, in which the coordination number of K atoms increases from 6 to 12, becoming two-dimensional (2D) metal nitrides with the highest coordination number. Nitrogen motifs in stable K–N monolayers depend on the nitrogen content (e.g., N2 dimer in KN2 and N20.5− dimer in KN4), and are accompanied by an electronic transition from superconducting to metallic. Intriguingly, the KN2 monolayer shows a unique superconducting energy gap with a calculated critical temperature (Tc) of 4.3 K under ambient conditions. The superconductivity is mainly derived from strong electron–phonon coupling (EPC) of the N 2p electrons and low- and mid-frequency K and N atomic vibrational modes. Our work provides key insight into 2D metal-bearing nitrides and the correlation between non-stoichiometry and conductivity mechanisms.

Graphical abstract: Unconventional stoichiometric two-dimensional potassium nitrides with anion-driven metallicity and superconductivity

Supplementary files

Article information

Article type
Paper
Submitted
12 ១០ 2023
Accepted
23 ១១ 2023
First published
23 ១១ 2023

J. Mater. Chem. C, 2024,12, 103-109

Unconventional stoichiometric two-dimensional potassium nitrides with anion-driven metallicity and superconductivity

Q. Yang, Y. Zhao, X. Jiang, B. Wang and J. Zhao, J. Mater. Chem. C, 2024, 12, 103 DOI: 10.1039/D3TC03718E

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