dos-analysis

name	dos-analysis
description	Use when the user asks about density of states (DOS), projected DOS (PDOS), d-band center, spin-resolved DOS, or electronic structure analysis from completed DFT calculations.

DOS and Electronic Structure Analysis

Overview

Density of states (DOS) analysis extracts electronic structure information from completed DFT calculations. Key quantities:

• Total DOS: overall electronic structure, band gap identification
• PDOS: orbital-resolved contributions from specific atoms
• d-band center: catalytic activity descriptor (higher = stronger binding)
• Spin-resolved DOS: magnetic ordering, spin polarization

MCP Tool: catgo_analyze

Total DOS

{"tool": "catgo_analyze", "arguments": {
  "action": "dos",
  "workflow_id": "wf_abc",
  "task_id": "task_sp",
  "dos_type": "total"
}}

Projected DOS (PDOS)

{"tool": "catgo_analyze", "arguments": {
  "action": "dos",
  "workflow_id": "wf_abc",
  "task_id": "task_sp",
  "dos_type": "projected",
  "atom_indices": [0, 1, 2, 3],
  "orbitals": ["d"]
}}

d-Band Center

{"tool": "catgo_analyze", "arguments": {
  "action": "dos",
  "workflow_id": "wf_abc",
  "task_id": "task_sp",
  "dos_type": "dband",
  "atom_indices": [0, 1, 2, 3]
}}

Returns:

• d_band_center: energy relative to Fermi level (eV)
• d_band_width: standard deviation of d-band (eV)
• d_band_filling: fraction of d-band occupied (0-1)

Workflow for DOS Analysis

DOS requires a completed single_point or geo_opt calculation with appropriate VASP settings.

VASP Settings for DOS

{"tool": "catgo_workflow_engine", "arguments": {
  "action": "add_task", "workflow_id": "wf_dos",
  "task_type": "single_point",
  "params": {
    "software": "vasp",
    "ENCUT": 520,
    "ISMEAR": -5,
    "NEDOS": 3001,
    "LORBIT": 11,
    "system_name": "DOS calculation"
  }
}}

Key VASP parameters:

• ISMEAR = -5: tetrahedron method with Blochl corrections (accurate DOS)
• NEDOS = 3001: number of DOS grid points (default 301 is too coarse)
• LORBIT = 11: write projected DOS (DOSCAR with atom/orbital decomposition)

Two-Step Pattern: Relax then DOS

{"tool": "catgo_workflow_engine", "arguments": {
  "action": "add_task", "workflow_id": "wf_dos",
  "task_type": "geo_opt",
  "params": {"software": "vasp", "ENCUT": 520, "system_name": "relax"}
}}

{"tool": "catgo_workflow_engine", "arguments": {
  "action": "add_task", "workflow_id": "wf_dos",
  "task_type": "single_point",
  "depends_on": "task_relax",
  "params": {
    "software": "vasp", "ENCUT": 520,
    "ISMEAR": -5, "NEDOS": 3001, "LORBIT": 11,
    "system_name": "DOS"
  }
}}

Python API

from catgo.workflow import Workflow

wf = Workflow("DOS analysis - Pt(111)")

inp = wf.add_task("structure_input", structure=pt_slab_json)

# Step 1: Geometry optimization
opt = wf.add_task("geo_opt",
    structure=inp.output.structure,
    software="vasp", ENCUT=520)

# Step 2: DOS single-point on relaxed structure
dos_sp = wf.add_task("single_point",
    structure=opt.output.structure,
    software="vasp", ENCUT=520,
    ISMEAR=-5, NEDOS=3001, LORBIT=11)

# Step 3: Post-process DOS
dos = wf.add_task("dos_analysis",
    doscar=dos_sp.output.doscar,
    atom_indices=[0, 1, 2, 3],
    orbitals=["d"],
    compute_dband=True)

wf.submit()

d-Band Center Theory

The d-band model (Hammer-Norskov) relates catalytic activity to the d-band center position relative to the Fermi level:

epsilon_d = integral(E * rho_d(E) dE) / integral(rho_d(E) dE)

Integrated over occupied states (up to Fermi level).

d-band center	Adsorbate binding	Catalytic implication
Higher (closer to E_F)	Stronger	More reactive, may over-bind
Lower (further from E_F)	Weaker	Less reactive, may under-bind

Surface vs Bulk d-Band

Surface atoms have narrower d-bands (fewer neighbors) and higher d-band centers than bulk atoms. Always select surface atom indices for catalysis analysis.

Spin-Resolved DOS

For magnetic systems (Fe, Co, Ni, oxides), enable spin polarization:

{"tool": "catgo_workflow_engine", "arguments": {
  "action": "add_task", "workflow_id": "wf_dos",
  "task_type": "single_point",
  "params": {
    "software": "vasp", "ENCUT": 520,
    "ISPIN": 2, "ISMEAR": -5, "NEDOS": 3001, "LORBIT": 11,
    "system_name": "spin-DOS"
  }
}}

Spin-resolved DOS returns separate up/down channels. The magnetic moment per atom equals the integral of (rho_up - rho_down) up to E_F.

Orbital Channels

Available orbital projections for PDOS:

Channel	Orbitals	Use Case
"s"	s	Main group elements
"p"	px, py, pz	O, N, C, S
"d"	dxy, dyz, dxz, dz2, dx2-y2	Transition metals
"f"	7 f-orbitals	Lanthanides, actinides

Specific sub-orbitals: "dz2", "dx2-y2", "dxy", "dxz", "dyz"

Common Pitfalls

1. Never use ISMEAR=1 (Methfessel-Paxton) for DOS -- it produces negative DOS artifacts. Use ISMEAR=-5 (tetrahedron) for static DOS calculations.
2. NEDOS=301 (VASP default) gives very coarse DOS. Use at least 2001-3001.
3. LORBIT=11 is required for PDOS. Without it, only total DOS is available.
4. Always do DOS as a separate single_point after geo_opt. The DOS from a relaxation run uses the smearing from NSW>0 and is unreliable.
5. For d-band center, select only surface layer atoms. Including bulk atoms averages out the surface electronic signature.
6. Band gap from DOS can be noisy -- compare with the band structure if precise gap values are needed.