  The interaction between screw dislocations and oxygen interstitial atoms is
studied with ab initio calculations in hexagonal close-packed titanium. Our
calculations evidence a strong repulsion when the solute atoms are located in
the dislocation glide plane, leading to spontaneous cross-slip, which allows
the dislocation to bypass the atomic obstacle. This avoidance process explains
several experimental observations in titanium in presence of oxygen: (1) a
larger lattice friction against screw dislocation motion, (2) a reduction of
the dislocation glide distance in prismatic planes and (3) an enhancement of
cross-slip in pyramidal planes.
