First-principles study of full $a$-dislocations in pure magnesium

Full $a$-dislocations on the $(0001)$ basal plane, $(10\bar10)$ prismatic plane, and $(10\bar11)$ and $(10\bar12)$ pyramidal planes in pure magnesium are investigated by using the Peierls–Nabarro model combined with generalized stacking fault (GSF) energies from first-principles calculations. The results show that the $(00\bar11)\langle11\bar20\rangle$ and $(10\bar12)\langle11\bar20\rangle$ slip modes have nearly the same GSF energy barriers, which are obviously larger than the GSF energy barriers of the $(0001)\langle11\bar20\rangle$ и $(10\bar10)\langle11\bar20\rangle$ slip modes. For both edge and screw full dislocations, the maximum dislocation densities, Peierls energies, and stresses of dislocations on the $(10\bar10)$, $(0001)$, $(10\bar11)$, and $(10\bar12)$ planes eventually increase. Moreover, the Peierls energies and the stresses of screw full dislocations are always lower than those of edge full dislocations for all slip systems. Dislocations on the $(10\bar11)$ and $(10\bar12)$ pyramidal planes possess smaller core energies, while the $(10\bar10)$ prismatic plane has the largest ones, implying that the formation of full dislocations on the $(10\bar10)$ plane is more difficult.