[Wien] Spin-orbit coupling SCF not converging

[Luigi Maduro - TNW]

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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