  Improving the high-temperature performance and low-temperature plasticity of
tantalum (Ta) alloys is a significant scientific challenge. We employed
first-principles calculations to study the interaction between screw
dislocations and solute atoms in the body centered cubic (BCC) structure of Ta,
with a particular focus on solid solution softening and strengthening. We
analyzed the impact of various solute elements on the generalized stacking
fault energy (GSFE), energy barriers within the single-atom column displacement
model, and their interaction with screw dislocations. The results indicate that
Hf and Zr, either individually or in combination, exhibit notable solute
softening effects in BCC Ta, significantly reducing GSFE, energy barriers, and
interaction energies. In contrast, Nb shows relative insensitivity to solute
effects, while Mo, W, and Ir demonstrate solute strengthening effects. The
calculations suggest that the interaction energy between screw dislocations and
solute atoms is a reliable indicator for predicting strengthening and softening
effects. Additionally, we extend these predictions to ternary alloys,
demonstrating that the strengthening and softening phenomena in these materials
can be explained through the electronic work function at the electronic level.
