Abstract
We investigated the effect of vacancy formation on brittle (D0
22
) to ductile (L1
2
-like) transition in Al
3
Ti using DFT calculations. The well-known pseudogap on the density of states of Al
3
Ti migrates towards its Fermi level from far above, via a W − M co-doping strategy, where M is Si, Ge, Sn or Pb respectively. In particular, by a W − M co-doping the underline electronic structure of the pseudogap approaches an octahedral (L1
2
: t
2g
, e
g
) from the tetragonal (D0
22
: e
g
, b
2g
, a
1g
, b
1g
) crystal field. Our calculations demonstrated that (1) a W-doping is responsible for the close up of the energy gap between a
1g
and b
1g
so that they tend to merge into an e
g
symmetry, and (2) all M-doping lead to a narrower gap between e
g
and b
2g
(moving towards a t
2g
symmetry). Thus, a brittle to ductile transition in Al
3
Ti is possible by adopting this W − M co-doping strategy. We further recommend the use of W-Pb co-doped Al
3
Ti to replace the less anodic Al electrode in Al-battery, due to its improved ductility and high Al diffusivity. Finally this study opens a new field in physics to tailor mechanical properties by manipulating electron energy level(s) towards higher symmetry via vacancy optimization.