alpha-SnF2: A UV Birefringent Material with Large Birefringence and Easy Crystal Growth

摘要

The simple binary fluoride alpha-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 alpha-SnF2 mainly benefits from well-aligned [SnF5] polyhedra with a strong SCALP. The exploration of the alpha-SnF2 birefringent crystal points out the direction of the future search for excellent birefringent materials.