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# Perform SOC calculations # Perform SOC calculations
To include spin-orbit coupling (SOC) into the system of study we take To include spin-orbit coupling (SOC) into the system of study we take
the scalar-relativistic Hamiltonian and add SOC in the Pauli-form $`\mathcal{H}_\mathrm{SO} = \xi \, L \cdot S`$. This is done by the the scalar-relativistic Hamiltonian and add SOC in the Pauli-form $`\mathcal{H}_\mathrm{SO} = \xi \, L \cdot S`$. This is done by the
new solver. **Note that the new solver works only for spin-polarized new solver. **Note that the new solver works only for spin-polarized
full potential calculations.** The features of the old solver like for full potential calculations.** The features of the old solver like for
example [DOS](jumu/density_of_states), example [DOS](jumu/density_of_states),
[QDOS](jumu/qdos), or [decimation](jumu/deci) work [QDOS](jumu/qdos), or [decimation](jumu/deci) work
as usual. The following steps are needed: as usual. The following steps are needed:
## Changes in the inputcard ## Changes in the inputcard
The options *NEWSOSOL* and *fullBZ* have to be set in the inputcard. The options `NEWSOSOL` and `fullBZ` have to be set in the inputcard.
This tells the program to use the new solver and to forget about all This tells the program to use the new solver and to forget about all
symmetries previously found for the current setup. This is needed since symmetries previously found for the current setup. This is needed since
SOC may break some symmetries. In addition some parameters for the SOC may break some symmetries. In addition some parameters for the
newsolver have to be set. These are *NPAN_LOG*, *NPAN_EQ*, newsolver have to be set. These are `NPAN_LOG`, `NPAN_EQ`,
*NCHEB* and *R_LOG*. Also do not forget to do spin-polarized `NCHEB` and `R_LOG`. Also do not forget to do spin-polarized
calculations for full potential (*NSPIN=2, KSHAPE=2*). If you started calculations for full potential (`NSPIN= 2, KSHAPE= 2`). If you started
with a calculation without spin-polarization, i.e. *NSPIN=1*, you can with a calculation without spin-polarization, i.e. `NSPIN= 1`, you can
[adopt your already converged potential](change_nspin_1_to_2). [adopt your already converged potential](change_nspin_1_to_2).
``` ```
RUNOPT RUNOPT
NEWSOSOL ... ... NEWSOSOL ... ...
+-------+-------+-------+-------+-------+ +-------+-------+-------+-------+-------+
` ***test options*** (2 lines) ` ` ***test options*** (2 lines) `
TESTOPT fullBZ TESTOPT fullBZ
+-------+-------+-------+-------+-------+ +-------+-------+-------+-------+-------+
... ...
NSPIN=2 NSPIN=2
... ...
KSHAPE=2 KSHAPE=2
... ...
HFIELD= 0.0 VCONST= 0.0d0 NPAN_LOG= 15 NPAN_EQ= 5 NCHEB= 12 R_LOG= HFIELD= 0.0 VCONST= 0.0d0 NPAN_LOG= 15 NPAN_EQ= 5 NCHEB= 12 R_LOG=
1.0d0 1.0d0
BZDIVIDE= 30 30 30 BZDIVIDE= 30 30 30
... ...
``` ```
If the new solver without SOC should be used the test If the new solver without SOC should be used the test
option *NOSOC* has to be added. option *NOSOC* has to be added.
## additional input files ## additional input files
Since the new solver does also deal with non-collinear calculations we Since the new solver does also deal with non-collinear calculations we
have to specify the non-collinear angles of each atom in the inputcard have to specify the non-collinear angles of each atom in the inputcard
in the file [nonco_angle.dat](nonco_angle.dat_file). If in the file [nonco_angle.dat](nonco_angle.dat_file). If
this file is not given then the angles are fixed to theta=phi=0 (i.e. this file is not given then the angles are fixed to theta=phi=0 (i.e.
the z-direction). the *z*-direction).
## Examples ## Examples
### Example 1: bulk Au with and without SOC ### Example 1: bulk Au with and without SOC
As an example the difference between bulk Au with and without SOC should As an example the difference between bulk Au with and without SOC should
be calculated. The test system consists of bulk Au (fcc lattice) with a be calculated. The test system consists of bulk Au (fcc lattice) with a
LMAX cutoff set to 2 and a k-mesh of 15x15x15, for the sake of speed of `LMAX= 2` cutoff and a *k*-mesh of 15x15x15, for the sake of speed of
the calculation. the calculation.
`{{:jumu/examples:au_bulk_nosoc_cos.tar.gz|Here}}`{=mediawiki} the input [Here](uploads/c9fb791a2f0f81c59ce73e77346fddbf/au_bulk_nosoc_cos.tar.gz) the input
files of both cases with the different inputcards can be found. Using files of both cases with the different inputcards can be found. Using
the [QDOS](jumu/qdos) the change in the band structure can be the [QDOS](jumu/qdos) the change in the band structure can be
investigated. investigated.
### Example 2: bulk Au with and without SOC ### Example 2: bulk Au with and without SOC
The second example is the SOC-induced splitting of Au(111) surface The second example is the SOC-induced splitting of Au(111) surface
states using a half-infinite Au(111) crystal (using the states using a half-infinite Au(111) crystal (using the
[decimation-technique](jumu/deci)) and the [decimation-technique](jumu/deci)) and the
[QDOS](jumu/qdos) option. [QDOS](jumu/qdos) option.
## TODO ## TODO
Addexample files with instructions, also to [examples page](jumu/examples_and_tips). Addexample files with instructions, also to [examples page](jumu/examples_and_tips).