4.4 Color plot of the Fermi velocity and the orbital character on Fermi surfaces

You can plot any quantity on Fermi surfaces as a color plot by using fermisurfer program¹. fermi_velocity.x and fermi_proj.x are used to generate an input file for fermisurfer from the output of pw.xor projwfc.x.

fermi_velocity.x generates a color-plot of Fermi velocity. You use it as follows:

1. Run pw.xwith K_POINT automatic.
2. Run

   $ fermi_velocity.x -in {pw.x input file}
   

3. vfermi.frmsf is generated

fermi_proj.x generates a color plot of an orbital character. You use it as follows:

1. Run pw.xwith K_POINT automatic.
2. Run projwfc.x just to generate {prefix}.save/atomic_proj.*.
3. Run

   $ fermi_proj.x -in {input file}
   

   Input-file format is as follows:

   &PROJWFC
    {The same as the input of projwfc.x}
   /
   {Number of target wavefunctions}
   {Index of target WFC1} {Index of target WFC2} {Index of target WFC3} ...
   

   It generates $\sum_{{i=1}}^{{n_{\rm target}}}$|$\langle$$\varphi_{{{\rm target}(i)}}^{{\rm atom}}$|$\varphi_{{n k}}^{}$$\rangle$|², where n_s and target(i) are the number of the target wavefunctions and the indices of target wavefunctions, respectively.
4. The above quantity is written into "proj.frmsf", which can be read by FermiSurfer program.

There is an example of fermi_velocity.x and fermi_proj.x in PP/example/fermisurf_example/.