and high-entropy alloys. Such disorder is, at low to intermediate temperatures, time independent (’quenched disorder’) and creates spatially fluctuating internal stresses and ensuing forces on the dislocations which depend on position and have zero average value. We use a simple model where a random force at the point $(x,y)$ is created by the superposition of forces from randomly located pinning points, each of which creates a Gaussian pinning potential: $$f(x,y)=\hat{f}\sum_{i=1}^{N}\frac{(x-x_{i})}{\xi}e^{-\frac{(x-x_{i})^{2}+(y-y_{i})^{2}}{2\xi^{2}}}.$$ Here $x_{i},y_{i}$ are the coordinates of pinning center $i$; $N$ is total number of randomly distributed pinning centers; $\xi$=$\sqrt{A/N}$ is the range of the pinning potential which also determines the correlation length of the random pinning force, and $\hat{f}$ defines the characteristic magnitude of the spatial force field.

![Top: determination of the pinning length, simulation with $\hat{f} = 0.04$N/m at zero applied stress; bottom: dependence of pinning length on amplitude $\hat{f}$ of the pinning field.[]{data-label="fig:pinlength"}](pinlength.pdf){width="3.3in"}

To quantify the action of the pinning force on the dislocation, we again consider the structure factor $R(d)$ which we evaluate for an ensemble of initially straight dislocations interacting with a pinning potential of range $\xi = 20 b$ and variable strength. During relaxation at zero applied stress, the dislocations develop local roughness as they 