We propose a low-temperature diffraction study at POLARIS of Prussian blue analogues (PBAs) of general formula NaxMM'(CN)6, where 1 < x 2. These systems currently attract intense research interest due to their potential applications as electrodes in sodium ion batteries. In order to fully understand the electrochemical processes, accurate structural models are vital. At present, the most favourable position of Na in the framework is debated and we believe that this diffraction study will be...