OD (order–disorder) interpretation and diffuse scattering analysis of an organic polytype with allotwin character: a detailed how-to

2,3-Dihydroxy-1,3,4-trimethyl-6-oxo-1,4-cyclohexadiene-1-carboxylic acid crystallizes in an order-disorder (OD) structure with a high stacking fault probability. The diffraction pattern features diffuse scattering and broad peaks, which can be attributed to fragments of two polytypes of a maximum degree of order (MDO). Additional weak peaks indicate existence of a non-MDO polytype. A detailed step-by-step instruction is given on how to develop an OD description and interpret the diffuse scattering using a stochastic growth model.