The phase-field method is suitable for simulations of structural changes with characteristic lengths of hundreds of nm and characteristic times from microseconds to miliseconds. This method is therefore useful for simulations of x-ray scattering data, where the coherence lengths/widths of the primary x-ray beam is of the same order. I will present first results of simulations of single-phase (mixed halide perovskites) and two-phase systems (growth of ω-Ti particles in β-Ti matrix). In the former case the method is capable to describe demixing of halide anions driven by free carriers, the aim of the latter topic is to describe the kinetics of beta to omega transition at low temperatures.