α-SnF2 : A UV Birefringent Material with Large Birefringence and Easy Crystal Growth
Jingyu Guo1,2, Abudukadi Tudi1,2, Shujuan Han1,2
1CAS Key Laboratory of Functional Materials and Devices for Special Environments, Xinjiang Technical Institute of Physics & Chemistry of CAS, Xinjiang Key Laboratory of Electronic Information Materials and Devices, 40-1 South Beijing Road, Urumqi, 830011, China.
Abstract:
The simple binary fluoride α-SnF2 is shown to be an excellent birefringent material with outstanding birefringence, about 14 times that of MgF2 . Furthermore, it exhibits a shorter UV cutoff edge and easy crystal growth at ambient temperature compared to YVO4 and TiO2 . A novel theoretical calculation mode was established to analyze the stereochemical-activity lone-pair (SCALP) contribution to the birefringence (SCB) based on the SCALP's strength and arrangement, and it was found that the large birefringence of α-SnF2 mainly benefits from well-aligned [SnF5 ] polyhedra with a strong SCALP. The exploration of the α-SnF2 birefringent crystal points out the direction of the future search for excellent birefringent materials.
