Structural progression between aragonite and postaragonite forms of nitride; a comparative study.

The BO3, B=C, N, Cl, ... systems all demonstrate aragonite and (where described) postaragonite structure types. The structural sequences exhibited by these different chemistries; however, differs in the detail: several intermediate forms and a host of metastable intermediates are identified. We wish to investigate their origin and rationalise their occurrence to give a better generalised view of the aragonite-postaragonite region of p, T structure-space.