High-pressure polymorphs of LiPN2: A first-principles study
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In this work, high-pressure phase behavior of LiPN2 within 0–300 GPa was studied by using an unbiased structure searching method in combination with first-principles calculations. Three pressureinduced phase transitions were predicted, as tI16 → hR4 → cF64 → oP8 at 44, 136, and 259 GPa, respectively. The six-fold coordination environments were found for all high-pressure polymorphs, which are substantially different from the four-fold coordination environments observed in the tI16 structure. The hR4 and cF64 structures consist of close-packed PN6 and LiN6 octahedra connected by edge-sharing, whereas the oP8 structure is built up from edge- and face-sharing PN6 and LiN6 octahedra with N lying in the center of the trigonal prisms. The electronic structure analysis reveals that LiPN2 is a semiconductor within the pressure range studied and P-N and Li-N bonds are covalent and ionic, respectively. The results obtained are expected to provide insight and guidance for future experiments on LiPN2 and other alkali metal nitridophosphates.
Keywordslithium nitridophosphates phase transition high pressure first principles
The authors acknowledge funding support from the National Natural Science Foundation of China (Grant Nos. 11474128 and 11534003), Science Challenge Project (Grant No. TZ2016001), National Key Research and Development Program of China (Grant Nos. 2016YFB0201200, 2016YFB0201201, and 2016YFB0201204), and Program for JLU Science and Technology Innovative Research Team. Parts of the calculations were performed in the high-performance computing center of Jilin University.
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