Why UFexAl12−x phase does not crystallize with ThMn12-structure type, when x = 2?

The crystallographic structure of recently reported orthorhombic UFe2Al10 phase, which belongs to the YbFe2Al10-structure type is different from the well known tetragonal UFexAl12−x (3 < x < 8) having ThMn12-structure type. Comparative Density Functional Theory (DFT) study of the relative stability of the orthorhombic UFe2Al10 phase with respect to different models of tetragonal ThMn12-type structures with the same composition is carried out to explain this unusual phenomenon. It is shown that the fine interplay between the overlapping of 3d-states of Fe and 5f-states of U in the region −2.5 ÷ −0.3 eV below the Fermi energy dictates the lower total energy of orthorhombic UFe2Al10 phase in comparison with tetragonal UFe2Al10 phase crystallized in ThMn12 structure. On the example of UFe2Al10 it is also directly demonstrated that DFT calculations in the framework of the Full Potential + Linear Augmented Plane Wave method within the local density approximation may be used for refining the structure of complicate compounds. The calculated equilibrium volume, lattice parameters and atomic Wyckoff positions of UFe2Al10 intermetallic compound are in very good agreement with experimental data.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Crystallographic structure UFe2Al10 is different from UFexAl12−x (3 < x < 8). ► Comparative DFT used to explain this unusual phenomenon. ► Energy, density of states and crystallography were considered. ► Calculated physical properties well agree with experiments.