During his PhD thesis prepared within the RheoMan project, S. Mahendran has performed atomistic modelling of the cores of screw dislocations with  Burgers vectors. It is found that at low pressure, the core tends clearly to spread in (010) leading to a well defined (010) slip system.
At higher pressure (i.e. above ca. 2 GPa), the situation is more complex with several configurations spreading in different planes and corresponding to different relative stabilities.
This complex energy landscape leads potentially to complex glide paths which leads, at the macroscopic planes to “non-crystallographic” glide also called “pencil glide” as observed experimentally.
See the orieginal reference (open access):
S. Mahendran, P. Carrez, P. Cordier (2019) On the glide of  dislocations and the origin of “pencil glide” in Mg2SiO4 olivine. Philosophical Magazine, 99(22), 2751-2769, https://doi.org/10.1080/14786435.2019.1638530