Heteroanionic [VOxS4-x] Groups: Tetrahedral Units with Large Birefringence for Mid-infrared Nonlinear Optical Crystals

Tetrahedral groups comprising [VO x S 4− x ] ( x = 0–4) units have the potential to enhance birefringence characteristics. Their balanced mid-IR NLO attributes make them a promising avenue of investigation for the exploration of NLO materials.