Prediction of Stable Ground-State Binary Sodium-Potassium Interalkalis under High Pressures
Abstract
The complex structures and electronic properties of alkali metals and their alloys provide a natural laboratory for studying the interelectronic interactions of metals under compression. A recent theoretical study (J. Phys. Chem. Lett. 2019, 10, 3006) predicted an interesting pressure-induced decomposition-recombination behavior of the Na2K compound over a pressure range of 10 - 500 GPa. However, a subsequent experiment (Phys. Rev. B 2020, 101, 224108) reported the formation of NaK rather than Na2K at pressures above 5.9 GPa. To address this discordance, we study the chemical stability of different stoichiometries of NaxK (x = 1/4, 1/3, 1/2, 2/3, 3/4, 4/3, 3/2 and 1 - 4) by effective structure searching method combined with first-principles calculations. Na2K is calculated to be unstable at 5 - 35 GPa due to the decomposition reaction Na2K-> NaK + Na, coinciding well with the experiment. NaK undergoes a combination-decomposition-recombination process accompanied by an opposite charge-transfer behavior between Na and K with pressure. Besides NaK, two hitherto unknown compounds NaK3 and Na3K2 are uncovered. NaK3 is a typical metallic alloy, while Na3K2 is an electride with strong interstitial electron localization.
Keywords
Cite
@article{arxiv.2101.03459,
title = {Prediction of Stable Ground-State Binary Sodium-Potassium Interalkalis under High Pressures},
author = {Yangmei Chen and Xiaozhen Yan and Huayun Geng and Xiaowei Sheng and Leilei Zhang and Hao Wang and Jinglong Li and Ye Cao and Xiaolong Pan},
journal= {arXiv preprint arXiv:2101.03459},
year = {2021}
}
Comments
19 pages, 4 figures, with supporting information