Prediction of open-framework aluminophosphate structures using the automated assembly of secondary building units method with Lowenstein's constraints

In this paper, we describe an approach to generate hypothetical open-framework aluminophosphate structures with specified Al/P stoichiometry using the automated assembly of secondary building units method. For each specified Al/P stoichiometry, all the possible combinations of Al and P atoms with different coordination states could be calculated according to the Lowenstein's rule. The Al and P atoms of different coordination states, together with the clusters constructed by them, could be selected as the building units for the structure generation. To satisfy the Lowenstein's rule, additional constraints are introduced into the simulation. The force field which controls the assembly of the building units is parametrized to favor the formation of Al-O-P linkages while avoiding the formation of Al-O-Al or P-O-P linkages. This method will not only aid the prediction of hypothetical aluminophosphate frameworks but also serve as a tool to set up the initial structural models for the solution of unknown aluminophosphate structures.