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A3Sc(PO4)2 (A = Li, Na): rare earth cations effectively regulate phosphate structures for enhanced birefringence
Hongheng Chen1, Xudong Leng1, Mei Hu1
1Xinjiang Key Laboratory of Solid State Physics and Devices, School of Physical Science and Technology, and Key Laboratory of Oil & Gas Fine Chemicals, Ministry of Education and Xinjiang Uyghur Autonomous Region, School of Chemical Engineering and Technology, Xinjiang University, Urumqi 830017, China. qunjing@xju.edu.cn.
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Phosphates possessing a rich variety of structural types and intriguing properties are widely used in fields such as ionic conductors, phosphors, and nonlinear optical materials. In this paper, two novel rare earth phosphates, A3Sc(PO4)2 (A = Li, Na), were successfully predicted using the artificial bee colony (ABC) algorithm along with ab initio total-energy calculations. The results of electronic structure and optical property calculations indicate that A3Sc(PO4)2 (A = Li, Na) not only retains the advantage of the large bandgap (Eg) of phosphates but also ameliorates the defects of the smaller birefringence (Δn) of phosphates (Li3Sc(PO4)2: Eg = 6.077 eV and Δn = 0.046@1064 nm; Na3Sc(PO4)2: Eg = 5.085 eV and Δn = 0.058@1064 nm). The real-space atom-cutting (RSAC) results show that the birefringence of A3Sc(PO4)2 (A = Li, Na) is mainly derived from the ScO6 group. This study enriches the variety of rare earth phosphates and confirms that the introduction of rare earth cations is an effective strategy for obtaining phosphates with a balance of a large bandgap and suitable birefringence.
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