Abstract
The results of X-ray diffraction measurements of a lead magnoniobate single crystal-PbMg13/Nb23/O3, performed on a four-circle diffractometer with Mo K alpha radiation, are described. It is confirmed that even at relatively high temperatures lead ions are shifted from the high-symmetry position. It is shown that these shifts are random both in length and direction. A spherical layer model is proposed for the adequate description of the experimental data. The correspondence between the crystal structure and the physical properties of the crystal is discussed.