M4LiBe4P7O24and M4Li(Li3P)P7O24(M = Cs, Rb): deep-ultraviolet nonlinear-optical phosphates with a tetrahedra-substituted paracelsian-like framework

New paracelsian-like beryllophosphates M(4)LiBe(4)P(7)O(24)and their tetrahedra-substituted phases M4Li(Li3P)P7O24(MLiP2O6, M = Cs, Rb) were designed and synthesized. Interestingly, two types of phases undergo a structural transformation, resulting from the radius and valence charge number of tetrahedral cations. Four crystals demonstrate potential deep-UV NLO properties such as short absorption edges (<190 nm) and phase-matching SHG response.