rubato-bgw-pw2bgw

name: rubato-bgw-pw2bgw
user-invokable: true
description: Generate pw2bgw.inp for QE → BerkeleyGW format conversion (WFN, RHO, VXC, VSC, VKB)
argument-hint: "[parent:cNNN] [calc_id:cNNN] [options...]"

Generate pw2bgw.inp for the pw2bgw.x executable (Quantum ESPRESSO → BerkeleyGW wavefunction conversion).

Usage

rubato:bgw-pw2bgw [parent:cNNN] [calc_id:cNNN] [options...]

• parent:cNNN — Parent QE nscf calculation. Required to extract prefix, outdir, k-grid (nk1, nk2, nk3), and nbnd.
• calc_id:cNNN — Save pw2bgw.inp to calc_db/{calc_id}/input/. If omitted, save to current directory.
• Any namelist field can be overridden as field=value (e.g., outdir=./out).

Execution

Step 1: Read parent nscf input

If parent:cNNN is given, read calc_db/{parent_dir}/input/pw.in to extract:
- prefix — from &CONTROL prefix = '...'
- outdir — from &CONTROL outdir = '...'
- nk1, nk2, nk3 — from K_POINTS automatic card (first three integers)
- nbnd — from &SYSTEM nbnd = ...

Step 2: Construct pw2bgw.inp

Always write the full namelist:

&input_pw2bgw
  prefix        = '{prefix}'
  outdir        = '{outdir}'
  real_or_complex = 2
  wfng_flag     = .true.
  wfng_file     = 'WFN'
  wfng_kgrid    = .true.
  wfng_nk1      = {nk1}
  wfng_nk2      = {nk2}
  wfng_nk3      = {nk3}
  wfng_dk1      = 0.0
  wfng_dk2      = 0.0
  wfng_dk3      = 0.0
  rhog_flag     = .true.
  rhog_file     = 'RHO'
  vxcg_flag     = .true.
  vxcg_file     = 'VXC'
  vxc_flag      = .true.
  vxc_diag_nmin = 1
  vxc_diag_nmax = {nbnd}
  vscg_flag     = .true.
  vscg_file     = 'VSC'
  vkbg_flag     = .true.
  vkbg_file     = 'VKB'
/

Step 3: Show and save

1. Show the complete pw2bgw.inp to the user.
2. Ask for confirmation or modifications.
3. Save to calc_db/{calc_id}/input/pw2bgw.inp if calc_id is given, or ./pw2bgw.inp otherwise.

Validation

Before saving, check:
- wfng_nk1, wfng_nk2, wfng_nk3 must all be > 0. Die with a clear error if any are zero (parent k-grid not found).
- vxc_diag_nmax must equal nbnd from the parent nscf. Warn if not.

Rules

• Always set real_or_complex = 2. BerkeleyGW GW calculations always use complex wavefunctions.
• Always output all five file types: WFN, RHO, VXC (both vxcg and vxc matrix elements), VSC, VKB. These are all required for the full GW workflow.
• vxc_diag_nmax must equal the parent nbnd. The sigma code reads vxc.dat for all bands.
• outdir must match the parent pw.x outdir exactly so pw2bgw.x can find the QE output files.
• Show the complete pw2bgw.inp before saving. Never write without user confirmation.
• When saving to a calc directory, always use the input/ subdirectory: calc_db/{calc_id}/input/pw2bgw.inp.
• If no parent is given and k-grid is unknown, ask the user for nk1, nk2, nk3 and nbnd explicitly.