The local structure of ferroelectric Pb1-xGexTe

The narrow band-gap semiconductor Pb1-xGexTe has a low-temperature ferroele ctric rhombohedral phase whose average structure is a distorted rock salt s tructure. We have measured the Extended X-ray Absorption Fine-Structure spe ctra of Pb1-xGexTe with x approximate to 0.3 at the Ge and Te K edges and a t the Pb-III edge. Guided by first-principles calculations, we create a mod el for the the local structure as a distortion from the ideal rock salt str ucture. By co-refining the spectra from these three edges, we demonstrate t hat the data are consistent with our fitting model. Our results show the po wer of using first-principles calculations in conjunction with EXAFS measur ements to determine local structures in complex materials.