First-principles investigations of the structural and mechanical stability of lanthanide intermetallics LnTl 3 (Ln = La, Ce, Pr, Gd, Dy and Lu)

In this study, we used first-principles simulations to investigate the electronic and elastic properties and structural and mechanical stability of lanthanide-based intermetallic LnTl 3 (Ln = La, Ce, Pr, Gd, Dy, Lu). Exchange-correlation effects were treated by generalized gradient approximation (GGA) and the GGA-Sol functional. The 4f peaks of LnTl 3 are located in the unoccupied states above the Fermi level, with a prominent peak around 2.48eV. The strong overlapping of orbitals due to the decrease in ionic radii of the Ln strengthens the interatomic bonding. The C[Formula: see text] of the understudy intermetallics gradually increases from La to Dy due to the lanthanide contraction effect. The phonon dispersion spectra of LnTl 3 (Ln = La, Ce, Pr, Gd, Dy and Lu) show the absence of imaginary frequencies across the entire Brillouin zone, confirming that the understudy intermetallics are dynamically stable in their optimized structures. The lanthanide contraction effect, in which the heavier Ln atoms produce lower vibrational frequencies because of their greater mass and shorter interatomic distances, is consistent with the phonon frequencies gradually moving as the atomic mass of the lanthanide element increases.