A New KBBF-Family Nonlinear Optical Material with Strong Interlayer Bonding

A new beryllium-free borate Rb3Ba3Li2Al4B6O20F features a layered structure analogous to that of the solely available deep-ultraviolet nonlinear optical (NLO) material KBe2BO3F2 (KBBF), and thus preserves its outstanding linear and nonlinear optical properties to a great extent. Furthermore, the interlayer bonding in Rb3Ba3Li2Al4B6O20F is significantly reinforced, with a magnitude of more than 15.6 times that of KBBF. As a result, a bulk Rb3Ba3Li2Al4B6O20F crystal is successfully grown in the preliminary experiments. The result demonstrates that the Rb3Ba3Li2Al4B6O20F crystal may have no (or only a tiny) layering growth habit, which severely hinders the practical applications of KBBF. Notably, Rb3Ba3Li2Al4B6O20F overcomes the structural instability problem present in the notable KBBF-family member Sr2Be2B2O7. These results make Rb3Ba3Li2Al4B6O20F a promising candidate for the next generation of deep-ultraviolet NLO materials. First-principles calculations are performed to elucidate the optical properties and structural stability.