1 Institute of Atomic and Molecular Physics, College of Physical Science and Technology, Sichuan University, Chengdu 610065, China;
2 National Key Laboratory of Shock Wave and Detonation Physics, Institute of Fluid Physics, China Academy of Engineering Physics, Mianyang 621900, China;
3 School of Science, Jiangxi University of Science and Technology, Ganzhou 341000, China
The application of high pressure can fundamentally modify the crystalline and electronic structures of elements as well as their chemical reactivity, which could lead to the formation of novel materials. Here, we explore the reactivity of lithium with sodium under high pressure, using a swarm structure searching techniques combined with first-principles calculations, which identify a thermodynamically stable Li-Na compound adopting an orthorhombic oP8 phase at pressure above 355 GPa. The formation of Li-Na may be a consequence of strong concentration of electrons transfering from the lithium and the sodium atoms into the interstitial sites, which also leads to open a relatively wide band gap for LiNa-oP8. This is substantially different from atoms sharing or exchanging electrons in common compounds and alloys. In addition, lattice-dynamic calculations indicate that LiNa-oP8 remains dynamically stable when pressure decompresses down to 70 GPa.
Project supported by the National Natural Science Foundation of China (Grant Nos. 11672274, 11274281, and 11174214), the China Academy of Engineering Physics Research Projects (Grant Nos. 2012A0101001 and 2015B0101005), the Joint Fund of the National Natural Science Foundation of China and the China Academy of Engineering Physics (NSAF) (Grant No. U1430117), and the Fund of National Key Laboratory of Shock Wave and Detonation Physics of China (Grant No. 6142A03010101).
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