yambo Documentation

PWscf to yambo interface (p2y): indirect approach

This approach makes use of the pw_export.x executable, and the low-level IOTK library routines of Giovanni Bussi, both part of the standard Quantum-ESPRESSO distribution.

Step 1: Configuring p2y

Make sure you have access to the library $ESPRESSO/iotk/src/libiotk.a in your Quantum-ESPRESSO distribution. You may have to create it with make libiotk.
Configure p2y, specifying BOTH the location of the iotk directory as well as the export option:
```
./configure --with-iotk='$ESPRESSO/3.2/iotk' --with-p2y=export
```
We strongly recommend that you install and link with a netCDF library.
```
        --with-netcdf='/usr/local/'
```
Check that configure found the links properly. You should see:
```
# [X] PW (export) support
# [X ] NETCDF/Large Files
```
Make the p2y executable in $yambo/bin:
```
make interfaces
```

Step 2: Create the unformatted pw.x datafiles.

Perform a self consistent run with PWscf (pw.x) in the usual manner.
Perform a non-self-consistent calculation with pw.x (bands or nscf), making sure to
- include many unoccupied bands,
- converge well the unoccupied states,
- generate a set of k-points that spans the full (or half) BZ, according to the symmetries
For example:
```
 &control
    calculation = 'bands'
 /
 &system
   nosym = .false.
   nbnd  = 200,
 /
 &electrons
    diago_thr_init = 1.0e-6
    diago_full_acc = .true.
 /
 K_POINTS {automatic}
 8 8 8 1 1 1
```
You should now have various .save/.pot/.rho/.wfc files.

Step 3: Export data from PWscf into XML-like format

In your Quantum-ESPRESSO distribution, make sure that the executable pw_export.x has been compiled (make pw_export).

Make an input file for pw_export.x, e.g.:

 heaven % cat export.in
 &inputpp
    prefix='cheese-out'
    outdir='./',
    single_file=.false.,
    ascii = .false.
    pseudo_dir = '/home/cdhogan/Research/PSEUDO/UPF',
    psfile(1)='H.pz-bhs.UPF'
    psfile(2)='S.pz-bhs.UPF'
/

Run the pw_export.x code in the directory containing the .save/.pot/.rho file:
```
 ./pw_export.x < export.in > export.out 
```
There should now be a (e.g.) cheese-out.export directory containing the index.xml/grid.*/wfc.* files.

Step 4: Convert data to the yambo format with p2y

Enter the [prefix].export directory, and run p2y with the required options, e.g.
```
cd cheese-out.export
$yambo/bin/p2y -S -N
```
Check the databases that are now in the SAVE directory. If you have linked to netCDF, you can inspect the files directly, e.g.:
```
ncdump SAVE/ns.db1 | less
```
See this page for a description of the yambo database format.
Otherwise you can ask yambo to report on the contents:
```
$yambo/bin/yambo -D -N
```
All ok? Well done: you are now ready to try the full yambo experience!

Still having problems? Try:

Tips and troubleshooting advice.