The prospect of beryllium–oxygen anionic group, especially (BeO3)4− anionic group, as the basic structural unit to search for new nonlinear optical (NLO) crystals is evaluated by anionic group theory and density functional theory. Our calculations reveal that the birefringence of the crystals containing only beryllium–oxygen anionic group is too small to satisfy the conditions of good NLO crystals for vacuum ultraviolet (VUV) applications, although the microscopic NLO coefficients of coplanar (BeO3)4− group is comparable to that of (BO3)3− group.
