solute atoms as strong pinning centers. Labusch [@Labusch1970_PSS; @Labusch1972_AM] developed a statistical model to consider describe the interaction between dislocations and solute atoms where the solute atoms act as weak pinning centres atoms. The Fleischer model is appropriate to dilute solid solutions, where spacings between solute atoms are large, whereas the Labusch model is suitable for concentrated solid solutions and has been also applied to high entropy alloys (HEAs) [@Toda2015_AM; @Wu2016_AM; @Varvenne2016_AM; @Varvenne2017_AM]. Note that the concepts of ’strong’ vs ’weak’ pinning do not relate to the magnitude of the CRSS: In highly dilute solid solutions, the CRSS is low but pinning may be ’strong’ in the above defined technical sense, whereas in HEA the CRSS is high but pinning may be technically ’weak’.

Theoretical approaches to dislocation pinning, envisaged as elastic manifold pinning, often rely on a line tension approximation. This idea may be problematic in HEA where the atomic scale disorder may be strong and cause roughening of dislocations down to the nanometre scale, such that the minimal dislocation ’wavelength’ is no longer small compared to the dislocation core radius. Here we investigate systematically the corrections that need to be applied to standard pinning theories as a consequence. 