We propose to use high resolution neutron powder diffraction for the study of the nuclear structure of Pb(CD3COO)2.3D2O in its low-temperature phase and to characterise with high-precision the evolution of the cell parameters and vibrational frequencies through the transition. The high resolution data will allow us to index uniquely the unit cell of the low temperature phase and solve the structure via ab-initio methods from the powder data. We also propose to use the experiment to commission the HRPD/Raman powder cell.