Atomic scale modeling of {110} twist grain boundaries in -iron: Structure and energy properties

Atomic scale modeling was used to study the structure and energy of {110} twist grain boundaries (TWGBs) with various coincidence-site-lattice misorientations in α-iron. The small angle {110} TWGB contains a hexagonal dislocation network of two sets of 1/2 〈111〉 and one set of 〈001〉 dislocation segments. The 〈001〉 segments are almost pure screw dislocations and the angle between the two 1/2111 segments varies from 83 to 109° for the rotation angle from 0.25 to 5.40°. This TWGB dislocation structure agrees well with an experimental observation that was not explained adequately so far. The large-angle TWGBs consist of periodic patterns rather than a dislocation network. The variation of the boundary energy with the rotation angle can be well fitted to the Read-Shockley equation in the low-angle range. An apparent cusp in the curve of the boundary energy against the rotation angle has been found and discussed.