rubato-qe-plotbands

name: rubato-qe-plotbands
user-invokable: true
description: Plot band structure from Quantum Espresso bands.x XML output
argument-hint: " [--labels \"G M K G\"] [--erange -4 4] [--out bands.png] [--title \"Title\"] [--spin 0]"

Plot band structure from a Quantum ESPRESSO bands.x XML output file.

Prerequisites

pip install numpy matplotlib

Usage

rubato:qe-plotbands <xml_file> [--labels "G M K G"] [--erange -4 4] [--out bands.png] [--title "Title"] [--spin 0]

Arguments

Label shorthand

G or GAMMA → Γ. All standard k-point symbols are supported as-is (M, K, A, L, H, X, …).

Execution

Run the bundled Python script:

python {skill_dir}/qe_plotbands.py <xml> [options]

Workflow

When the user asks to plot a band structure:

1. Identify the XML file (look for *.xml in the current directory if not specified; prefer files in bands/ or */bands.save/)
2. Ask the user for k-path labels if not provided (e.g., "G M K G")
3. Run:
   bash python {skill_dir}/qe_plotbands.py <xml> --labels "<labels>" [--erange <emin> <emax>] [--out <png>] [--title "<title>"]
4. Report the output PNG filename

Examples

# Basic — no labels
python {skill_dir}/qe_plotbands.py bands/pwscf.xml

# With k-path labels
python {skill_dir}/qe_plotbands.py bands/pwscf.xml --labels "G M K G A L H A"

# Custom energy window and output
python {skill_dir}/qe_plotbands.py bands/pwscf.xml --labels "G M K G" --erange -6 4 --out ws2_bands.png --title "2H-WS2"

# Spin-down channel
python {skill_dir}/qe_plotbands.py bands/pwscf.xml --labels "G M K G" --spin 1

Output

Saves a <name>_bands.png figure (200 dpi, 3.3×3.3 in) with:
- Bands aligned to Fermi energy (E − E_F)
- Vertical lines at high-sym k-points
- Dashed horizontal line at E = 0

Rules

• Always ask for k-path labels if not provided. The plot is much more useful with labeled high-symmetry points.
• Show the output PNG path after plotting so the user can open it.
• If the XML file is not found, search for *.xml in common locations (bands/, */bands.save/, ./out/).
• For spin-polarized calculations, inform the user that --spin 0 (up) is default and --spin 1 plots down channel.
• If calc_id context is available, look for the XML file in calc_db/{calc_id}/output/ or similar paths.