surface-creation

name	surface-creation
description	Workflow and pitfalls for generating crystal surfaces (slabs) from bulk structures.
when_to_use	Use when the user asks for a surface, slab, Miller-indexed face, or surface termination. Read this BEFORE invoking any surface-building tool.

Surface Creation

Instruction-only skill (no entry script). Use it as a checklist when planning a surface-generation task. For deeper material-specific notes, drill down via:

• references/lpscl_and_sio2.md — worked examples for LPSCl (Li6PS5Cl) and α-SiO2 surfaces.
• references/checklist.md — validation checklist and PBC / vacuum / layer-count rules of thumb.

Common Workflow

1. Obtain bulk crystal structure

   • Materials Project search (preferred for real materials), or
   • Manual creation via crystal-builder skill / pymatgen / ASE.

2. Convert to conventional cell (CRITICAL for FCC)

   • MP often returns primitive cells (60° angles for FCC).
   • For surfaces, use the conventional cell. The structure tools accept need_conventional=True.
   • Never hand-roll cell transformations — use proper tools.

3. Generate surface using SlabGenerator

   • Specify Miller indices.
   • Layers: 4–8 (5 is a good default for DFT).
   • Vacuum: ≥ 10–15 Å.

4. Build supercell for desired adsorbate coverage

   • Periodic images of any adsorbate must be > 10 Å apart.

5. Validate (Miller indices, termination, surface coordination, PBC=(T,T,F), structural-unit integrity).

6. Save and document (.extxyz preferred; record MP ID, orientation, layers, vacuum thickness).

Key Considerations

Miller indices and stability

• BCC: (100), (110), (111). (110) often most stable.
• FCC: (111) most stable, (100) common.
• Perovskites: (001) common, multiple terminations.
• Oxides: (001), (100), (101), (110).

Primitive vs. conventional cell

Cell type	Angles	Use case
Primitive	60° (rhombohedral)	Bulk calculations
Conventional	90° (cubic)	Surface generation

Common pitfalls

Pitfall	Fix
Primitive vs. conventional cell	Convert to conventional BEFORE surface generation.
Wrong surface termination	Check all terminations, pick one preserving units.
Insufficient vacuum	Increase to ≥ 10 Å.
Too many layers for DFT	Reduce to 5; verify properties hold.
Adsorbate periodic images < 10 Å	Enlarge supercell.
Broken structural units (PS4, dimers)	Test all terminations; see lpscl_and_sio2 reference.