Abstract: AlPO₄-5 molecular sieve is one of typical aluminophosphates molecular sieves,which has a main porous system of 12 member rings. It belongs to hexagonal system. Now we had found the structure can be derived into a lot of orthogonal framework structures. In this paper, the 64 topological framework structures of analogues correlated to AlPO₄-5 in the orthorhombic system have been designed by the computer modelling technique. Their theoretical X-ray powder diffraction patterns have beem calculated, and the probability of their existence has been discussed. The X-ray powder diffraction patterns of a synthesized orthogonal AlPO₄-5 are in good agreement with the theoretical ones, It proves the existence of materials of orthogonal AlPO₄-5.

Key words: AlPO₄-5, Orthorhombic system, Framework topological structure