We then used HPPXRD, using the same methodology, to determine B as a function of x (Fig. ). Within standard errors, we observe an increasing B as a function of x in [PEP]1-x[DPP]xNi(C2N3)3 (Tables and). This points at a close to ideal solid solution behaviour and suggests the absence of strong coupling effects, 57 e.g. behaviour that could arise from the ordering of [PEP] + and [DPP] + .