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

Abstract

Full a-dislocations on the (0001) basal plane, $$(10\bar 10)$$ prismatic plane, and $$(10\bar 11)$$ and $$(10\bar 12)$$ 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 $$\left( {10\bar 11} \right)\left\langle {11\bar 20} \right\rangle$$ and $$\left( {10\bar 12} \right)\left\langle {11\bar 20} \right\rangle$$ slip modes have nearly the same GSF energy barriers, which are obviously larger than the GSF energy barriers of the $$\left( {0001} \right)\left\langle {11\bar 20} \right\rangle$$ and $$\left( {10\bar 10} \right)\left\langle {11\bar 20} \right\rangle$$ slip modes. For both edge and screw full dislocations, the maximum dislocation densities, Peierls energies, and stresses of dislocations on the $$(10\bar 10)$$ , (0001), $$(10\bar 11)$$ , and $$(10\bar 12)$$ 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 $$(10\bar 11)$$ and $$(10\bar 12)$$ pyramidal planes possess smaller core energies, while the $$(10\bar 10)$$ prismatic plane has the largest ones, implying that the formation of full dislocations on the $$(10\bar 10)$$ plane is more difficult.