Crystal structure and optical properties of a new nickel magnesium diphosphate

•Pure Nickel diphosphate MgNiP2O7 synthesized by coprecipitation method.•Structural determination/refinement of this compound revealed that both Mg and Ni atoms are located in the two octahedral and square pyramid sites.•Relationship between structural refinement and UV analysis are studied.•Two optical band gaps were obtained for the sample suggesting direct allowed transitions which are in good agreement with MgNiP2O7 structure.