Uncovering a Vital Band Gap Mechanism of Pnictides

Pnictides are superior infrared (IR) nonlinear optical (NLO) material candidates, but the exploration of NLO pnictides is still tardy due to lack of rational material design strategies. An in-depth understanding structure-performance relationship is urgent for designing novel and eminent pnictide NLO materials. Herein, this work unravels a vital band gap mechanism of pnictides, namely P atom with low coordination numbers (2 CN) will cause the decrease of band gap due to the delocalization of non-bonding electron pairs. Accordingly, a general design paradigm for NLO pnictides, ionicity-covalency-metallicity regulation is proposed for designing wide-band gap NLO pnictides with maintained SHG effect. Driven by this idea, millimeter-level crystals of MgSiP2 are synthesized with a wide band gap (2.34 eV), a strong NLO performance (3.5 x AgGaS2), and a wide IR transparency range (0.53-10.3 mu m). This work provides an essential guidance for the future design and synthesis of NLO pnictides, and also opens a new perspective at Zintl chemistry important for other material fields.

Automated summary

This work unravels a vital band gap mechanism of pnictides and proposes a general design paradigm for wide-band gap nonlinear optical pnictides. The synthesis of millimeter-level crystals of MgSiP2 with a wide band gap and strong nonlinear optical performance demonstrates the effectiveness of this method. This research provides essential guidance for the future design and synthesis of pnictide materials.