The obtained structure after relaxation, which is similar to the tetrahedral configuration, exhibits a formation energy equal to the one given by the authors for the hexagonal one.
Obviously, the authors did not check the relaxed structure still assuming a hexagonal configuration.
The actual structure is equal to the tetrahedral configuration, which is slightly displaced along the three coordinate axes.
Variations exist with displacements along two or a single \hkl<1 0 0> direction indicating a potential artifact.
However, finite temperature simulations are not affected by this artifact due to a low activation energy necessary for a transition into the energetically more favorable tetrahedral configuration.
The obtained structure after relaxation, which is similar to the tetrahedral configuration, exhibits a formation energy equal to the one given by the authors for the hexagonal one.
Obviously, the authors did not check the relaxed structure still assuming a hexagonal configuration.
The actual structure is equal to the tetrahedral configuration, which is slightly displaced along the three coordinate axes.
Variations exist with displacements along two or a single \hkl<1 0 0> direction indicating a potential artifact.
However, finite temperature simulations are not affected by this artifact due to a low activation energy necessary for a transition into the energetically more favorable tetrahedral configuration.