Theoretical investigation of structural stability and lattice vibrations of U6Fe16Si7 and its interstitial carbide U6Fe16Si7C

A series of lattice inversion pair potentials are used to evaluate the phase stability and site preference for uranium intermetallics U6Fe16Si7 and its interstitial carbide U6Fe16Si7C. The calculated preferentially occupation site of the Si atom is found to be the 4a site. Interstitial C atom can only be located on the 4b site. Calculated lattice constants are found to agree with a report in the literature. It is noted that the total and partial phonon densities of states are first evaluated for the U6Fe16Si7 and U6Fe16Si7C compounds. The analysis for the inverted potentials explains qualitatively the contributions of different atoms to the vibrational modes.