Structure Builder

Loading Structures

From Online Databases

• catgo_fetch_crystal — Load crystal by formula or structure_id from OPTIMADE providers (mp=Materials Project, mc3d, alexandria, twodmatpedia, omdb)
• catgo_search_crystals — Search and list multiple matches. Use this first when browsing, then catgo_fetch_crystal with a specific structure_id.
• catgo_fetch_molecule — Fetch molecules from PubChem by name, formula, or SMILES.

Provider heuristics:

• General inorganic crystals: mp (largest database)
• 2D materials: twodmatpedia
• Organic molecules: use catgo_fetch_molecule, not OPTIMADE

From Current Viewer

Call catgo_structure_info to inspect the loaded structure. All structure-modifying tools auto-fetch the current viewer structure — no need to pass structure dicts.

Atom-Level Operations

Tool	Use When
catgo_add_atom / catgo_add_atoms	Adding atoms at Cartesian positions (Angstroms)
catgo_delete_atoms	Removing atoms by 0-based index
catgo_replace_atom	Changing element at a site
catgo_move_atom / catgo_move_atoms	Repositioning atoms

Lattice and Cell Operations

Tool	Use When
catgo_supercell	Expanding unit cell by [na, nb, nc] or 3x3 matrix
catgo_set_lattice	Adding/changing periodic cell (wraps molecules in a box)
catgo_merge	Combining two structures at a given position

Defect Engineering

Tool	Use When
catgo_build_defect	Point defects: vacancy, substitution, interstitial
catgo_doping	Substitutional doping (replace host with dopant)
catgo_substitution	Combinatorial multi-site substitution
catgo_intercalation	Insert species (Li, Na) into layered structures
catgo_build_strain	Apply strain/deformation (Voigt notation or 3x3 matrix)

Nanostructures

Tool	Use When
catgo_nanotube_build	Carbon or BN nanotubes from chiral indices (n, m)
catgo_nanotube_info	Compute nanotube geometry before building

Common Recipes

Doped supercell

1. catgo_fetch_crystal → 2. catgo_supercell → 3. catgo_doping → 4. catgo_structure_info

Defective structure for DFT

1. Fetch bulk → 2. catgo_supercell (large enough to avoid defect-defect interaction) →
2. catgo_build_defect → 4. catgo_structure_info

Intercalated battery material

1. catgo_fetch_crystal (e.g. MoS2) → 2. catgo_intercalation (species="Li") → 3. Verify