Structural instability and ground state of the U2Mo compound

This work reports on the structural instability at T = 0 °K of the U2Mo compound in the C11b structure under the distortion related to the C66 elastic constant. The electronic properties of U2Mo such as density of states (DOS), bands and Fermi surface (FS) are studied to understand the source of the instability. The C11b structure can be interpreted as formed by parallel linear chains along the z-directions each one composed of successive U-Mo-U blocks. Hybridization due to electronic interactions inside the U-Mo-U blocks is slightly modified under the D6 distortion. The change in distance between chains modifies the U-U interaction and produces a split of f-states. The distorted structure is stabilized by a decrease in energy of the hybridized states, mainly between d-Mo and f-U states, together with the f-band split. Consequently, an induced Peierls distortion is produced in U2Mo due to the D6 distortion. It is important to note that the results of this work indicate that the structure of the ground state of the U2Mo compound is not the assumed C11b structure. It is suggested for the ground state a structure with hexagonal symmetry (P6 #168), ∼0.1 mRy below the energy of the recently proposed Pmmn structure.