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Fabricating van der Waals Heterostructures with Precise Rotational Alignment
Published on: July 5, 2019
AVP2S7 (A = K, Rb): Dual-Optimized Infrared Nonlinear Optical Thiophosphates via Heterovalent-Substitution-Driven
Shao-Peng Gui1, Zheng-Ren Chen1, Wei-Hua Yan1
1Yunnan Key Laboratory of Electromagnetic Materials and Devices, School of Materials and Energy, Yunnan University, Kunming650500, P. R. China.
Abstract:
Transforming centrosymmetric (CS) materials into noncentrosymmetric (NCS) analogues through rational structural modification is an effective pathway for designing nonlinear optical (NLO) materials. Herein, we demonstrate a heterovalent-substitution-driven symmetry-breaking transformation from CS V2P2S6 (C2/m) to NCS AVP2S7 (A = K, Rb) (C2). The introduction of alkali metal cations reconstructs the staggered checkerboard array of [VS6] octahedra into alternately arranged [AS8] bicapped trigonal prisms and [VS6] octahedra, thereby eliminating the inversion center. Simultaneously, the weak van der Waals interactions between the {[V2P2S6]}∞ neutral layers are replaced by the {[VP2S7]-}∞ polyanionic layers with strong electrostatic ionic bonds of alkali metal cations, significantly enhancing the structural stability. AVP2S7 exhibit a second harmonic generation response of 0.5 × AgGaS2 together with enhanced laser-induced damage thresholds. Theoretical calculations reveal that the NLO activity primarily originates from the cooperative alignment of [P2S7] dimers. This study establishes a heterovalent substitution strategy that simultaneously achieves symmetry breaking and structural stabilization, providing a rational route for developing new infrared NLO materials.
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