Chen Yangmei, Yan Xiaozhen, Geng Huayun, Sheng Xiaowei, Zhang Leilei, Wang Hao, Li Jinglong, Cao Ye, Pan Xiaolong
School of Science, Jiangxi University of Science and Technology, Ganzhou 341000, Jiangxi, People's Republic of China.
National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, CAEP, P.O. Box 919-102, Mianyang 621900, Sichuan, People's Republic of China.
Inorg Chem. 2021 Jan 4;60(1):124-129. doi: 10.1021/acs.inorgchem.0c02506. Epub 2020 Dec 22.
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 ( , 10, 3006) predicted an interesting pressure-induced decomposition-recombination behavior of the NaK compound over a pressure range of 10-500 GPa. However, a subsequent experiment ( , 101, 224108) reported the formation of NaK rather than NaK at pressures above 5.9 GPa. To address this discordance, we study the chemical stability of different stoichiometries of NaK ( = 1/4, 1/3, 1/2, 2/3, 3/4, 4/3, 3/2, and 1-4) by an effective structure searching method combined with first-principles calculations. NaK is calculated to be unstable at 5-35 GPa due to the decomposition reaction NaK → 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 NaK and NaK are uncovered. NaK is a typical metallic alloy, while NaK is an electride with strong interstitial electron localization.
