Electronic mechanism of shear modulus enhancement in rare earth intermetallics Yb1−xTmxAl3

Rare earth elements doped thermoelectric materials Yb1−xMxAl3 (M = Ho, Er and Tm) demonstrated anomalously enhanced shear modulus [Zhou J et al, Intermetallics, 2010; 18:2394]. However, the origin of the shear modulus enhancement has not yet been understood. In this work, we shed light on this mechanism by systematically analyzing the band structure and charge density near the Fermi energy of Yb1−xTmxAl3 under various shear stresses on the basis of ab initio total energy calculations. We have showed that the valence band maximum (VBM) is very sensitive to shearing and plays an important role for the shear modulus enhancement. Since the valence electron structures of Ho, Er and Tm in Yb1−xMxAl3 (M = Ho, Er and Tm) alloys are very similar, the present results will provide a fundamental understanding on the electronic origin of shear properties in these rare earth intermetallics.

Graphical abstractFigure optionsDownload full-size imageDownload as PowerPoint slideHighlights► Based on DFT calculations, Yb1−xMxAl3 (M = Ho, Er and Tm) compounds have been investigated. ► The shear modulus c44 for the Yb1−xMxAl3 alloys reaches a maximum at x = 0.5. ► The VBM of Yb1−xTmxAl3 is very sensitive to shearing and plays a vital role for understanding the c44 behavior. ► The decomposed charge-density distribution of VBM was studied.