VASP Router

Route VASP requests to the appropriate sub-skill based on the calculation type.

Routing Table

User intent	Route to
Geometry optimization, relaxation, structural optimization	relax/SKILL.md
Single point energy, SCF calculation	static/SKILL.md
Density of states (DOS, PDOS, d-band center)	dos/SKILL.md
Band structure, electronic bands	band/SKILL.md
Vibrational frequencies, ZPE, thermodynamics	freq/SKILL.md
Ab initio molecular dynamics (AIMD)	md/SKILL.md

VASP-Specific Policies — ALWAYS enforce these

1. POTCAR selection

POTCAR is handled automatically by the HPC engine based on the structure's elements. You do NOT need to specify POTCAR files. The engine uses the recommended POTCARs (e.g., Ti_pv, O, Ru_pv).

If the user requests specific POTCARs (e.g., _sv variants), pass them via:

wf.add_task(geo_opt, structure=s, POTCAR_MAP={"Ti": "Ti_sv", "O": "O"})

2. ENCUT selection

Default: 520 eV (suitable for most oxide catalysts).

Guidelines:

• Bulk metals: 400-520 eV usually sufficient
• Oxides and surfaces: 520 eV recommended
• Convergence tests: test 400, 450, 500, 550, 600 eV
• If user specifies ENCUT, respect it without question

3. K-points

K-points are auto-generated from the structure's cell dimensions. Override with:

wf.add_task(geo_opt, structure=s, KPOINTS=[4, 4, 1])  # Gamma-centered

Slab guideline: use [N, N, 1] where N gives ~0.03 A^-1 spacing in-plane.

4. ISPIN for magnetic systems

Default: ISPIN=1 (non-spin-polarized).

Set ISPIN=2 for:

• Transition metals: Fe, Co, Ni, Mn, Cr
• Their oxides: Fe2O3, CoO, NiO, MnO2
• Any system where user mentions magnetism or spin

wf.add_task(geo_opt, structure=s, ISPIN=2, MAGMOM="5*4.0 10*0.6")

5. Slab calculations — frozen layers

For surface slabs, ALWAYS freeze bottom layers:

# Typical 4-layer slab: freeze bottom 2 layers
wf.add_task(geo_opt, structure=slab,
            ISIF=2,           # Fix cell shape (mandatory for slabs)
            selective_dynamics=True,
            freeze_layers=2)  # Freeze bottom 2 layers

Rules:

• ISIF must be 2 for slabs (never 3 — that allows cell shape change)
• Freeze at least the bottom half of slab layers
• Adsorbate atoms are always free to move

6. Dispersion corrections

For adsorption studies, consider DFT-D3:

wf.add_task(geo_opt, structure=s, IVDW=11, LDAU=False)

Only add if user requests it or the system involves weak interactions (physisorption, vdW heterostructures).

Config Defaults (from ~/.catgo/config.yaml)

These are the system defaults. Only specify parameters that differ:

defaults.vasp:
  ENCUT: 520
  EDIFF: 1e-5
  PREC: Accurate
  ALGO: Fast
  ISMEAR: 0
  SIGMA: 0.05
  LREAL: Auto
  NELM: 200
  ISPIN: 1
  LORBIT: 11
  LWAVE: False
  LCHARG: False
  NCORE: 4

Quick Examples

Bulk relaxation

wf.add_task(geo_opt, structure=bulk_json, ISIF=3, system_name="bulk_TiO2")

Slab relaxation with frozen layers

wf.add_task(geo_opt, structure=slab_json, ISIF=2,
            freeze_layers=2, system_name="TiO2_110_slab")

Single point after relaxation

opt = wf.add_task(geo_opt, structure=s, system_name="opt")
sp = wf.add_task("single_point", structure=opt.output.structure, system_name="SP")

Full OER chain (per adsorbate)

opt = wf.add_task(geo_opt, structure=s, ISIF=2, freeze_layers=2, system_name="*OH")
frq = wf.add_task(freq, structure=opt.output.structure,
                  freeze_mode="layers", freeze_layers=4, system_name="*OH")
gib = wf.add_task(gibbs_energy, energy=opt.output.energy,
                  frequencies=frq.output.frequencies, system_name="*OH")

MCP Workflow Creation

catgo_workflow_engine(action="create", params={"name": "VASP relaxation"})
# → {"workflow_id": "wf_xxx"}

catgo_workflow_engine(action="add_task", params={
  "workflow_id": "wf_xxx",
  "task_type": "geo_opt",
  "software": "vasp",
  "structure": "<json>",
  "ISIF": 2,
  "system_name": "slab_relax"
})

catgo_workflow_engine(action="submit", params={"workflow_id": "wf_xxx"})

Common Mistakes to Avoid

1. Using ISIF=3 for slabs (allows cell to change shape — unphysical for surfaces)
2. Forgetting to freeze bottom slab layers (all atoms relax toward vacuum)
3. Using ISMEAR=0 for metals (should use ISMEAR=1, SIGMA=0.2 for metals)
4. Setting LREAL=.FALSE. for large cells >200 atoms (use LREAL=Auto)
5. Not setting ISPIN=2 for magnetic systems (wrong energetics)