1D Crystalline Assemblies Exhibiting Large Second Harmonic Generation Susceptibilities and Stacking‐/Polarization‐Driven Tunability

Abstract Nonlinear optical (NLO) van der Waals (vdW) crystals containing 1D building blocks exhibit large NLO coefficients and birefringence that are crucial for their applications. In this work, 21 NLO 1D building blocks with large second harmonic generation (SHG) susceptibility from the Computational 1D Materials Database (C1DB) are screened. Among them, 14 are hitherto unreported and have SHG susceptibilities approaching theoretical upper limits. Forty‐five new vdW NLO crystals are then constructed by stacking one or two of the 21 building blocks. Eighteen of them inherit the large SHG susceptibilities of their corresponding 1D building blocks. Three stable crystals exhibit large SHG susceptibilities and birefringence, while one stable crystal possesses ferroelectricity. Interestingly, the SHG susceptibilities of the newly constructed NLO crystals are inversely proportional to the third power of their bandgaps. Further calculations show that the SHG susceptibilities of the vdW NLO crystals can be tuned either by stacking order or by reversing electric polarization, providing possibilities for their application in tunable nonlinear optics and NLO switches.