[Wien] Spin-orbit coupling SCF not converging

[Peter Blaha]

lapwso should work for surface slabs.

Is it a magnetic system ??  Probably not.

My guess: these slabs get metallic and you used TETRA ??? The 
additionally degeneracy may cause problems.
For a 2D system always use TEMP(S) and some smearing (conservative: 2 
mRy; to get improved scf-convergence increase it (temporarily) to 10 mRy

For such large cells I'd start with a small Emax (NBAND) and after 
convergence recheck with a larger value (it depends what quantities do 
you want to calculate with SO).



On 11/26/19 2:21 PM, Luigi Maduro - TNW wrote:
> Hello there WIEN2k users,
> 
> I am having a convergence problem with a supercell calculation of a slab 
> of MoS2 including Spin-Orbit Coupling (SOC). The supercell is made by 
> cutting in the plane of MoS2 which leads to either only edge Mo atoms or 
> edge S atoms. A vacuum parallel to the edges is introduced (about 18 
> angstroms) that separates the repeating images. Converged SCF 
> calculations without SOC were found with this type of geometry for 
> various widths. These converged SCF calculations were then used as input 
> for an SCF calculation with SOC for the different widths. However, when 
> including SOC only the smallest width gave a converged SCF calculation, 
> albeit after doubling the amount of k-points and increasing nbands(more 
> than twice what was originally suggested when running init_so). The 
> larger widths do not result in a converged SCF calculation, even after 
> substantially increasing nbands. Is the solution to just keep on 
> increasing the amount of k-points until I do get converged SCF 
> calculations or is the inclusion of the vacuum giving problems for lapwso?
> 
> As a side not, I have a general question on how to relate Emax and 
> nbands in case.in1. Up until recently I have been using SCALAPACK in 
> WIEN2k and now I have switched to using ELPA. In the case of MoS2, a 
> system with large spin-orbit coupling, the userguide recommends to 
> increase the value of Emax to up to 10 Ry for large SOC systems when 
> running the init_so script. If one is using ELPA then nbands should be 
> increased. In the case of ELPA should nbands be increased to twice the 
> amount given in case.in1 when initially running init_so?
> 
> PhD candidate
> Kavli Institute of Nanoscience
> 
> Department of Quantum Nanoscience
> 
> Faculty of Applied Sciences
> 
> Delft University of Technology
> 
> 
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-- 

                                       P.Blaha
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Peter BLAHA, Inst.f. Materials Chemistry, TU Vienna, A-1060 Vienna
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Email: blaha at theochem.tuwien.ac.at    WIEN2k: http://www.wien2k.at
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