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# Restraints

Restraints narrow the database search by pre-filtering cards that do not match specified chemical or crystallographic criteria.

Open Search → Restraints.

## Properties tab

Field | Description
--- | ---
Chemical name | Filter by compound name (partial match)
Color | Filter by crystal color
Density (calc.) | Filter by calculated density ± tolerance
Density (meas.) | Filter by measured density ± tolerance

## Composition tab

Field | Description
--- | ---
Elements | Include/exclude chemical elements
Mode | `Contains` (AND/OR), `Only` (exact composition), `Just` (at least these)

## Symmetry tab

Field | Description
--- | ---
Crystal system | Filter by crystal system (cubic, tetragonal, …)
Space group | Filter by space group symbol
Cell parameters | Filter by unit cell constants a, b, c, α, β, γ ± tolerance

## Entries tab

Paste a list of card IDs (one per line) to restrict the search to those specific entries.

## Subfiles tab

Filter by PDF-2 subfile codes (e.g., `I` = inorganic, `O` = organic).

## Buttons

Button | Action
--- | ---
Load cards | Query the database with the current restraints (replaces results)
Load & Merge | Query and add results to the current list
Search & Match | Run a FOM-ranked search within the restrained subset