Command findinter

Command: findinter

findinter builds PAIPAI struc.in files from a metal-only POSCAR.

Basic Usage

findinter \
  --input POSCAR_metal_only \
  --inter B,O \
  --internum 4,5 \
  --gn 100 \
  --min-void-factor 0.9 \
  --max-void-factor 1.2 \
  --output struc.in \
  --site-poscar interstitial_sites.vasp

radii.dat is an input file. If it is missing, findinter creates a default template and exits before generating struc.in. Inspect or edit radii.dat, then rerun the same command.

Required Options

Option	Default	Meaning
--inter B,O	required	Comma-separated interstitial element names.
--internum 4,5	required	Comma-separated number of occupied interstitial atoms for each interstitial species. Must match --inter length.
one grid mode	required	Exactly one of --gn, --gnx --gny --gnz, or --gstep.

Although --input has an internal default of POSCAR, the command-line help expects an explicit metal-only POSCAR.

File Options

Option	Default	Meaning
--input POSCAR	POSCAR	Metal-only input POSCAR.
--output FILE	struc.in	Output PAIPAI structure file.
--site-poscar FILE	empty	Optional POSCAR containing metal atoms plus H markers at candidate interstitial sites.
--radii FILE	radii.dat	Input file containing effective hard-sphere radii. If missing, a default template is created and the program exits.
-h, --help	-	Show help.

radii.dat Input Format

The radii file is plain text with one key-value pair per line:

# PAIPAI findinter hard-sphere radii in Angstrom
Nb 1.428
Ta 1.428
Ti 1.428
Hf 1.428
Interstitial 0.55

Each metal species in the input POSCAR must have a radius entry. The special Interstitial entry is required and controls the effective size used for candidate interstitial sites.

Parameter meaning:

Entry	Meaning
Metal symbol, e.g. Nb 1.428	Effective hard-sphere radius for that metal species. Larger values exclude more nearby grid points.
Interstitial 0.55	Effective interstitial search radius. Smaller values permit denser candidate-site placement; larger values suppress nearby candidate sites more strongly.

These radii are site-search parameters, not fixed tabulated atomic radii. They work together with --min-void-factor and --max-void-factor.

Grid Options

Exactly one grid mode must be provided.

Option	Default	Meaning
--gn N	unset	Same grid count along x, y, and z. Values are clamped to at least 1.
--gnx N --gny N --gnz N	unset	Explicit grid counts along x, y, and z. All three must be provided together. Values are clamped to at least 1.
--gstep X	unset	Target Cartesian grid step in Angstrom. Must be positive.

Site Selection Options

Option	Default	Meaning
--max-sites N	0	Maximum number of candidate sites to write. 0 means no limit.
--min-void-factor X	1.0	Require nearest-metal distance at least X * (r_metal + r_interstitial). Must be positive.
--max-void-factor X	2.0	Reject points farther than X * (r_metal + r_interstitial) from the nearest metal. Must be positive.
--merge-distance X	0.0	Optional extra merge distance for nearly duplicate selected sites. Negative values are clamped to 0.

--min-void-factor must be less than or equal to --max-void-factor.

Output

Typical outputs:

File	Meaning
struc.in	PAIPAI input structure with metal and interstitial candidate sites.
interstitial_sites.vasp	Optional visualization POSCAR.

radii.dat is not considered a successful-run output. It is an input file. The automatic creation behavior is only a template-generation step for missing radii files.