Set up

All BGW examples should be run from your scratch folder. First, copy the tutorial bundle to your scratch folder:

cd /lustre/scratch5/<moniker>
cp -rP /usr/projects/laccmss2025/bgw_tutorial ./
ls

There are 4 important folders here:

1a-silicon_mfs
1a-silicon_mfs-run
3a-silicon_bse
3a-silicon_bse-run

• 1a-silicon_mfs folder contain the instructions to run the the GW calculations

The 3a-silicon_bse contain the instructions to run the the BSE calculations. They require the output from 1a-silicon_mfs .

The *-run folders are the prebuilt examples, including all binary output.

Because we are focusing on the BSE calculations and have limited time, we suggest you run directly the BSE calculations. Still, you have two options

Option 1 (recommended): skip the GW calculation

You don’t need to do anything. The default behavior of this tutorial is to reuse prebuilt GW calculations, and some prebuilt DFT calculations. Still, you’ll need to rerun the DFT calculations.

<aside>

⚠️ FIX

We just updated the 1a-silicon_mfs-run folder! Go to your main scratch folder, get rid of the previous 1a-silicon_mfs-run folder, and copy the updated version

rm -rf 1a-silicon_mfs-run
cp -rP /usr/projects/laccmss2025/bgw_tutorial/1a-silicon_mfs-run ./

</aside>

Option 2: explicitly run the DFT or GW calculation (do it later)

If you wish to do the GW calculation yourself, including the underlying DFT calculations, then first go the 1a-silicon_mfs folder and run the example. The example allows you to use several DFT codes. Only Quantum ESPRESSO was tested in this computer.

Afterwards, before you run the BSE calculations in the 3a-silicon_bse folder, you will need to slightly modify linking scripts, because you want to reuse data from your own calculations, from 1a-silicon_mfs, instead of the premade ones in 1a-silicon_mfs-run:

• For the mean-field part: go to 3a-silicon_bse/1-mf folder and, under each subdirectory (e.g., 1-scf), you will find a 01-reuse_files.sh script. Open each of these scripts, replacing the variable src from 1a-silicon_mfs-run to 1a-silicon_mfs.
• Do a similar change in the 3a-silicon_bse/2-bgw folder.

Running the BSE example

To run the BSE example, simply go to the 3a-silicon_bse folder and follow the instructions in the README.md file.

Important: Always read the README.md files before running anything! They contain the required steps for the calculations and questions to make sure you understand the process to run a GW-BSE calculation.