|  |  | ###### Perform SOC calculations {#perform_soc_calculations} | 
|  |  |  | 
|  |  | 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 | 
|  |  | new solver. \_\_Note that the new solver works only for spin-polarized | 
|  |  | full potential calculations.\_\_ The features of the old solver like for | 
|  |  | example [DOS](jumu:density_of_states "wikilink"), | 
|  |  | [QDOS](jumu:qdos "wikilink"), or [decimation](jumu:deci "wikilink") work | 
|  |  | 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. | 
|  |  | 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 | 
|  |  | SOC may break some symmetries. In addition some parameters for the | 
|  |  | newsolver have to be set. These are //NPAN\_LOG//, //NPAN\_EQ//, | 
|  |  | //NCHEB// and //R\_LOG//. Also do not forget to do spin-polarized | 
|  |  | calculations for full potential (//NSPIN=2, KSHAPE=2//). If you started | 
|  |  | with a calculation without spin-polarization, i.e. *NSPIN=1*, you can | 
|  |  | [adopt your already converged | 
|  |  | potential](change_nspin_1_to_2 "wikilink"). <code> RUNOPT NEWSOSOL \... | 
|  |  | \... | 
|  |  | +\-\-\-\-\-\--+\-\-\-\-\-\--+\-\-\-\-\-\--+\-\-\-\-\-\--+\-\-\-\-\-\--+ | 
|  |  |  | 
|  |  | `     ***test options*** (2 lines) ` | 
|  |  |  | 
|  |  | TESTOPT fullBZ | 
|  |  | +\-\-\-\-\-\--+\-\-\-\-\-\--+\-\-\-\-\-\--+\-\-\-\-\-\--+\-\-\-\-\-\--+ | 
|  |  |  | 
|  |  | \... | 
|  |  |  | 
|  |  | NSPIN=2 | 
|  |  |  | 
|  |  | \... | 
|  |  |  | 
|  |  | KSHAPE=2 | 
|  |  |  | 
|  |  | \... | 
|  |  |  | 
|  |  | HFIELD= 0.0 VCONST= 0.0d0 NPAN\_LOG= 15 NPAN\_EQ= 5 NCHEB= 12 R\_LOG= | 
|  |  | 1.0d0 | 
|  |  |  | 
|  |  | BZDIVIDE= 30 30 30 | 
|  |  |  | 
|  |  | \... </code> If the new solver without SOC should be used the test | 
|  |  | option //NOSOC// has to be added. | 
|  |  |  | 
|  |  | ##### additional input files {#additional_input_files} | 
|  |  |  | 
|  |  | 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 | 
|  |  | in the file [nonco\_angle.dat](jumu:nonco_angle.dat_file "wikilink"). If | 
|  |  | this file is not given then the angles are fixed to theta=phi=0 (i.e. | 
|  |  | the z-direction). | 
|  |  |  | 
|  |  | ##### 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 | 
|  |  | 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 | 
|  |  | the calculation. | 
|  |  | `{{:jumu:examples:au_bulk_nosoc_cos.tar.gz|Here}}`{=mediawiki} the input | 
|  |  | files of both cases with the different inputcards can be found. Using | 
|  |  | the [QDOS](jumu:qdos "wikilink") the change in the band structure can be | 
|  |  | 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 | 
|  |  | states using a half-infinite Au(111) crystal (using the | 
|  |  | [decimation-technique](jumu:deci "wikilink")) and the | 
|  |  | [QDOS](jumu:qdos "wikilink") option. \<WRAP center round todo 60%\> Add | 
|  |  | example files with instructions, also to [examples | 
|  |  | page](jumu:examples_and_tips "wikilink"). </WRAP> |