Dear WIEN2k Users, I am trying to calculate the electronic structure (DOS, LDOS) of magnetic impurity/add on atom (Co) on the surface of silicene (i.e. Si graphene). While checking the convergence vs. the supercell size I've noticed the following artifact: the size of the magnetic moment on Co stays roughly constant (about 0.8 \mu_B) up until certain size of the supercell (say 9x9) and then starts growing, in some cases up to the atomic values (~3 \mu_B). I don't see how this could be physical, as the Co-silicene distance and the local geometry around impurity stays the same, however I was not able to find any obvious errors in my calculations.
The calculations for bulk silicene work well. I'm running 14.2 version, the vertical separation between silicene sheets is 14 Angst, the lattice constant is a=3.86 Angst. I've used rKmax between 3 and 7. The k-mesh was generated using (3,3,1) divisions but I've also tested with denser 2D meshes and the automatically generated meshes. The symmetry, determined during the initialization phase was the same in all the cases, e.g.: H LATTICE,NONEQUIV.ATOMS: 61 156 P3m1 I've started these calculations by extracting the geometry of local Co neighborhood from the relaxed calculations with 4x4 supercell and embedding it into bulk silicene when running larger supercells. The calculations were then performed with thus fixed geometry. However the same trends can be observed with unrelaxed geometry. In the latter case I fashioned the supercell out of bulk unit cell and then attached Co atom at arbitrary height. I'd be happy to provide further informations (structure files) and grateful for any hints you may give me. Kind Regards Maciej Zwierzycki PS. At the moment I'm trying to establish to what extent the results are sensitive to separation between silicene sheets. _______________________________________________ Wien mailing list Wien@zeus.theochem.tuwien.ac.at http://zeus.theochem.tuwien.ac.at/mailman/listinfo/wien SEARCH the MAILING-LIST at: http://firstname.lastname@example.org/index.html