Dislocation loop implementation

Faulted dislocation loops are implemented in DADOS as round-shaped structures of immobile interstitials, oriented in one of the four {111} planes. The orientation is randomly taken (from these four) when the dislocation loop is created.

The density of atoms in the dislocation loop is given by this expression:

By simplicity, DADOS implements the dislocation loop using a square in-plane lattice with planar density r.

In consequence, the distance between consecutive atoms is:

And the radius can be calculated by:

Emission

Dislocation loops emit interstitials from their edge end and they release them as a point defect from a randomly consen orientation of its surface.

The emission frequency is given by the expression:

Where:

• λ is the jump distance.

• D0DLoopProp is proportional to the prefactor.
• n is the dislocation loop size.
• Eb is the binding energy.
• Em is the migration energy of the released point defect.
• See symbol list.

Growth

When a mobile neutral interstitial is near enough to the dislocation loop (closer than the capture distance), it is captured by it and inserted into the edge.

Formation energy

Formation energy for faulted dislocation loops as a function of the radius is (Cristiano et al. 2000):

Where:

• r is the radius of the defect.

• g is the stacking fault energy per unit area.

• m is the shear modulus.

• n is the Poisson's ratio.

• r₀ is the dislocation core radius, where b is the modulus of the Burgers vector.

• See symbol list.

Shrinkage

As dislocation loops are relevant near equilibrium conditions (low supersaturation), the following process is not implemented:

V + I_n -> I_n-1

Complementary emission

Vacancy emission from dislocation loop (generation of a vacancy and a bound interstitial) is not currently implemented because it is not likely to occur.