Decomposition and Recombination of Binary Interalkali Na2K at High Pressures

Lihua Yang; Xin Qu; Xin Zhong; Dandan Wang; Yanli Chen; Jinghai Yang; Jian Lv; Hanyu Liu

doi:10.1021/acs.jpclett.9b00882

Decomposition and Recombination of Binary Interalkali Na₂K at High Pressures

J Phys Chem Lett. 2019 Jun 6;10(11):3006-3012. doi: 10.1021/acs.jpclett.9b00882. Epub 2019 May 22.

Authors

Lihua Yang^{1

2

3}, Xin Qu^{1

2

3}, Xin Zhong^{1

2

3}, Dandan Wang^{1

2

3}, Yanli Chen^{1

2

3}, Jinghai Yang¹, Jian Lv⁴, Hanyu Liu⁴

Affiliations

¹ Key Laboratory of Functional Materials Physics and Chemistry of the Ministry of Education , Jilin Normal University , Changchun 130103 , P. R. China.
² College of Physics , Jilin Normal University , Siping 136000 , China.
³ National Demonstration Center for Experimental Physics Education , Jilin Normal University , Siping 136000 , China.
⁴ State Key Laboratory of Superhard Materials, College of Physics , Jilin University , Changchun 130012 , China.

PMID: 31117694
DOI: 10.1021/acs.jpclett.9b00882

Abstract

Under compression, "'simple'" alkali metals and their alloys exhibit complex structural and electronic properties, leading to fundamental interest in their high-pressure behaviors. Here, the swarm-intelligence structure-searching method was employed to identify the high-pressure phases of binary interalkali Na₂K, which has long been known to possess a MgZn₂-Laves phase at ambient pressure, but the high-pressure behavior remains elusive. We uncovered four new structures over a pressure range of 10-500 GPa, although the compound was found to become unstable upon decomposition into Na and K from 37 to 273 GPa. In phases before decomposition, the electrons were gradually delocalized with an increase in pressure and there was charge transfer from K to Na, whereas in phases after recombination, the electrons were gradually localized into the interstitials of the crystals, showing the unexpected opposite trend of charge transfer from Na to K, remarkably, where K was found to exhibit an oxidation state beyond the -1 valence state. The results can improve our understanding of the interaction and evolution of s electrons under compression.