Anharmonic temperature factors up to sixth order and atomic potentials in the fast ionic conductor α-Ag 3SI

Abstract

The electron density of the fast ionic conductor α-Ag 3SI was investigated by single crystal X-ray data measured at 573 K. The silver ions in this bcc structure are distributed along bands parallel to 〈100〉. Symmetry-independent reflections could be refined to an R-value of 0.7% with partial occupancy of octahedral and tetrahedral sites. Anharmonic temperature factors up to the sixth order were applied to describe the smeared-out electron density. By means of the probability density functions calculated from these temperature factors the relevance of the refined parameters is discussed. From the experimentally determined atomic potentials an activation energy of 0.03 eV is estimated.