... A new method is proposed that makes it possible to determine the parameters of the three-dimensional (3D) multiwell potential of off-center atoms from extended X-ray absorption fine-structure (EXAFS) data. ... The parameters of the multiwell potential for Ge atoms in the Sn 1-x Ge x Te solid solution as functions of temperature and composition (77<T<300 K, x>0.4) were obtained in the classical approximation. ...