First-Principles Design of a Deep-Ultraviolet Nonlinear-Optical Crystal from KBe₂BO₃F₂ to NH₄Be₂BO₃F₂

KBe₂BO₃F₂ (KBBF) is so far the sole nonlinear-optical (NLO) material that can be practically applied in the deep-ultraviolet (DUV) region. For the purpose of overcoming its layering tendency in crystal growth, herein a computer-assisted material design system is employed to design a new KBBF analogue, ammonia beryllium fluoroborate (NH₄Be₂BO₃F₂, ABBF). The first-principles calculations demonstrate that ABBF possesses NLO properties very close to those of KBBF, thus exhibiting good DUV NLO capability. Moreover, owing to the relatively strong chemical binding between layers, ABBF would have a better growth habit compared with KBBF. Upon synthesis, ABBF would be a very promising DUV NLO material