# 21.6: Change in the Misfit Energy of a Dislocation as it Moves

- Page ID
- 31771

The dislocation remains fixed (at the origin) and the lattice moves around it, therefore the initial positions of atoms xA and xB are given by

\[x_{A}=n b-\alpha b\]

\[x_{B}=n b-b / 2-\alpha b\]

We use the same method as for the α = 0 case to determine the in-plane displacement and misalignment. As a result, the potentials for different α values can be determined. The following animation (which is a magnified version of the strain energy graph on the previous page) demonstrates how changing the parameter alpha affects the position of the energy minimum and the dislocation width.

By calculating the misfit energy for each value of alpha, we can determine the change in misfit energy ΔUT(α) as the dislocation moves.

- ΔU
_{T}(x) is the difference in total energy from α = x and α = 0. - At first, as the dislocation moves across the unit cell 0<|α|<0.25, ΔU
_{T}increases to a maximum. - At the maximum (α = 0.25), the value of ΔU
_{T}is the Peierls energy, ΔU_{P} - Then for 0.25<|α|<0.5, ΔU
_{T}decreases. At α = 0.5, ΔU_{T}= 0. - w also changes as the dislocation moves across the cell as seen. This is because the configuration of the dislocation changes as the dislocation moves across the unit cell. For the energy maxima, the dislocation width is also a maximum.