  We elucidated the core structure of screw dislocations in ordered B2 FeCo
using a recent magnetic bond-order potential (BOP) [Egorov et al., Phys. Rev.
Mater. 7, 044403 (2023)]. We corroborated that dislocations in B2 FeCo exist in
pairs separated by antiphase boundaries. The equilibrium separation is about 50
A, which demands large-scale atomistic simulations - inaccessible for density
functional theory but attainable with BOP. We performed atomistic simulations
of these separated dislocations with BOP and predicted that they reside in
degenerate core structures. Also, dislocations induce changes in the local
electronic structure and magnetic moments.
