Determination of the crystallographic structure of the new U ₆Fe₅Al₈Si₉ compound

The crystal structure of a new quaternary U₆Fe ₅Al₈Si₉ orthorhombic compound described by Immm space group was solved and refined on the basis of X-ray powder diffraction data. The unit cell parameters (a = 12.2407(2) , b = 18.3614(3) , c = 4.0662(1) ) and the atomic coordinates were optimized through Rietveld refinement procedure with the reliability factors R_p = 8.1%, R_b = 6.2% and R_wp = 11.4%. Density Functional Theory calculations were used to distinguish between positions of Si and Al atoms in the final model of the structure. The positions of heavy atoms observed in high-resolution TEM-images fit their positions on the respective projections of the proposed structural model.