Precision x-ray data on the electronic structure of fluorite

Two precision x-ray diffraction-data sets obtained on different instruments have been used to examine the details in the electron-density distribution for a natural fluorite crystal whose total YF3 + LnF3 impurity content was not more than 0.05 mole %. The main details from the two measurements coincide. The differences in the deformation electron density δρ do not exceed 3σ. There is excess δρ (about 0.1 e·angstrom-3) near the center of the octahedral cavity, which indicates that there are interstitial fluorine atoms. SrF2 + BaF2 contents were determined by chemical analysis, and those of YF3 + LnF3 by neutron activation