28: Diamond — plotting of MLWFs using Gaussian cube format and VESTA¶

Outline: Obtain MLWFs for the valence bands of diamond and output them in Gaussian cube format
Directory: tutorials/tutorial28/ The input files for this tutorials are the same as the ones in Tutorial 5 and can be downloaded here
Input Files
- diamond.scf The pwscf input file for ground state calculation
- diamond.nscf The pwscf input file to obtain Bloch states on a uniform grid
- diamond.pw2wan The input file for pw2wannier90
- diamond.win The wannier90 input file
Run pwscf to obtain the ground state of diamond
Terminal
```
pw.x < diamond.scf > scf.out
```
Run pwscf to obtain the Bloch states on a uniform k-point grid
Terminal
```
pw.x < diamond.nscf > nscf.out
```
Run wannier90 to generate a list of the required overlaps (written into the diamond.nnkp file).
Terminal
```
wannier90.x -pp diamond
```
Run pw2wannier90 to compute the overlap between Bloch states and the projections for the starting guess (written in the diamond.mmn and diamond.amn files).
Terminal
```
pw2wannier90.x < diamond.pw2wan > pw2wan.out
```
When the lattice vectors are non-orthogonal, not all the visualisation programs are capable to plot volumetric data in the Gaussian cube format. One program that can read volumetric data for these systems is VESTA. To instruct wannier90 to output the MLWFs data in Gaussian cube format you need to add the following lines to the .win file
Input file
```
wannier_plot           = .true.
wannier_plot_supercell = 3
wannier_plot_format    = cube
wannier_plot_mode      = crystal
wannier_plot_radius    = 2.5
wannier_plot_scale     = 1.0
```
Run wannier90 to compute the MLWFs and output them in the Gaussian cube file.
Terminal
```
wannier90.x diamond
```
Plot the first MLWF with VESTA vesta diamond_00001.cube

Extra: Instead of using wannier_plot_mode = crystal try to use the molecule mode as wannier_plot_mode = molecule (see the user guide for the definition of this keyword). Add the following line to the .win file:

Input file

restart = plot

and re-run wannier90. Use VESTA to plot the resulting MLWFs, do you see any difference from the crystal mode case? Can you explain why? Try to change the size of the supercell from 3 to 5, do you expect the results to be different? (Hint: When using the Gaussian cube format the code outputs the WF on a grid that is smaller than the super unit-cell. The size of the grid is specified by wannier_plot_scale and wannier_plot_radius.)