Vasp

Quick Parameter Guide

Essential INCAR Parameters

Energy Cutoff (ENCUT):

ENCUT = 520  # eV, typical for PAW potentials

• Default: 1.3 × ENMAX from POTCAR
• Recommendation: 1.3-1.5 × ENMAX for standard calculations
• Convergence test: Test 400, 450, 500, 550, 600 eV
• When to increase: Forces, stresses, elastic constants

k-Point Sampling:

# Method 1: Automatic mesh
KSPACING = 0.5  # Å⁻¹, automatic generation

# Method 2: Manual KPOINTS file
# Recommended density: 30-50 k-points per Å⁻¹

Precision (PREC):

PREC = Accurate  # High, Normal, Accurate

• Low: Fast, testing only
• Normal: Standard calculations
• Accurate: Forces, phonons, production

Electronic Convergence (EDIFF):

EDIFF = 1E-6  # eV, energy convergence

• Standard: 1E-6 eV
• Tight: 1E-8 eV (forces, phonons)
• Loose: 1E-4 eV (quick testing)

Input File Templates

INCAR: Control Parameters

# System description
SYSTEM = Cu bulk FCC

# Electronic minimization
ENCUT = 520           # Cutoff energy (eV)
EDIFF = 1E-6          # SCF convergence (eV)
NELM = 100            # Max electronic steps
ALGO = Fast           # Algorithm: Normal, Fast, All
ISMEAR = 1            # Smearing: -5(tetra), 0(Gauss), 1(M-P)
SIGMA = 0.2           # Smearing width (eV)

# Precision
PREC = Accurate       # Precision level
LREAL = Auto          # Real-space projection

# Ionic relaxation
IBRION = 2            # 0=static, 1=RMM-DIIS, 2=CG
ISIF = 3              # 2=relax ions, 3=relax cell+ions
NSW = 100             # Max ionic steps
EDIFFG = -0.02        # Force convergence (eV/Å)

# Output
LWAVE = .FALSE.       # Write WAVECAR
LCHARG = .FALSE.      # Write CHGCAR

POSCAR: Atomic Structure

Cu FCC bulk
1.0                    # Universal scaling
  3.61  0.00  0.00     # Lattice vectors
  0.00  3.61  0.00
  0.00  0.00  3.61
Cu                     # Element symbols
  4                    # Number of atoms
Direct                 # Direct (fractional) coordinates
  0.00  0.00  0.00
  0.50  0.50  0.00
  0.50  0.00  0.50
  0.00  0.50  0.50

Key Points:

• Line 1: Comment (system description)
• Line 2: Universal scaling factor
• Lines 3-5: Lattice vectors (Å)
• Line 6: Element symbols (must match POTCAR order)
• Line 7: Number of atoms per element
• Line 8: Coordinate type (Direct or Cartesian)
• Lines 9+: Atomic positions

KPOINTS: k-Point Sampling

Gamma-Centered Mesh (most common):

Automatic mesh
0                      # 0=automatic
Gamma                  # Gamma or Monkhorst-Pack
  8  8  8              # k-point grid
  0  0  0              # Shift

Monkhorst-Pack:

Automatic mesh
0
Monkhorst-Pack
  8  8  8
  0  0  0

Band Structure Path:

k-points for band structure
10                     # Number of points between high-symmetry points
Line-mode              # Line mode for band structure
Reciprocal
  0.0  0.0  0.0   !Γ
  0.5  0.0  0.5   !X

  0.5  0.0  0.5   !X
  0.5  0.25 0.75  !W

POTCAR: Pseudopotentials

Generation:

# Concatenate POTCARs in same order as POSCAR
cat ~/vasp/potpaw_PBE/Cu/POTCAR > POTCAR

# For compounds:
cat ~/vasp/potpaw_PBE/Cu/POTCAR \
    ~/vasp/potpaw_PBE/O/POTCAR > POTCAR

Choosing POTCARs:

• Standard: potpaw_PBE/Element/POTCAR
• GW calculations: potpaw_PBE.52/Element/POTCAR or potpaw_PBE.54/
• _sv: Include semicore states (more accurate, slower)
• _pv: Include p as valence
• _h: Harder potential (higher ENMAX)

Parameter Selection by Calculation Type

1. Structure Relaxation

INCAR:

IBRION = 2            # Conjugate gradient
ISIF = 3              # Relax cell + ions
NSW = 100
EDIFFG = -0.02        # Force convergence
ISMEAR = 1            # Methfessel-Paxton
SIGMA = 0.2

Convergence Criteria:

• EDIFFG < 0: Force-based (recommended: -0.01 to -0.05 eV/Å)
• EDIFFG > 0: Energy-based (less common)

2. Static Calculation (Single-Point)

INCAR:

IBRION = -1           # No ionic updates
NSW = 0
ISMEAR = -5           # Tetrahedron (accurate DOS)
# OR
ISMEAR = 0            # Gaussian (if tetra not converged)
SIGMA = 0.05

3. Band Structure

Step 1: Self-consistent calculation

ICHARG = 2            # From atoms
LCHARG = .TRUE.       # Write CHGCAR

Step 2: Non-self-consistent band structure

ICHARG = 11           # Read CHGCAR, no update
LORBIT = 11           # Write PROCAR
# Use line-mode KPOINTS

4. Density of States (DOS)

INCAR:

ISMEAR = -5           # Tetrahedron method
LORBIT = 11           # Projected DOS
NEDOS = 3000          # DOS resolution
# Use dense k-point mesh

5. Molecular Dynamics

INCAR:

IBRION = 0            # MD
NSW = 1000            # MD steps
POTIM = 1.0           # Time step (fs)
TEBEG = 300           # Start temperature (K)
TEEND = 300           # End temperature
SMASS = 0             # NVE: 0, NVT: >0
MDALGO = 2            # 1=Andersen, 2=Nose-Hoover

6. Phonons (DFPT)

INCAR:

IBRION = 6            # DFPT for phonons
NFREE = 2             # Central differences
POTIM = 0.015         # Displacement (Å)
EDIFF = 1E-8          # Tight convergence!

7. Elastic Constants

INCAR:

IBRION = 6            # DFPT
ISIF = 3
NFREE = 4             # For elastic constants

Advanced Parameters

Hybrid Functionals (HSE06, PBE0)

HSE06:

LHFCALC = .TRUE.      # Activate hybrid
HFSCREEN = 0.2        # HSE screening parameter
AEXX = 0.25           # Exact exchange fraction
ALGO = All            # Or Damped
TIME = 0.4            # Damping for convergence

GW Calculations

Step 1: DFT (PBE)

ALGO = Exact
NBANDS = 200          # Many empty bands
LOPTICS = .TRUE.

Step 2: GW

ALGO = GW0  # Or EVGW
NOMEGA = 50

DFT+U (Correlated Systems)

INCAR:

LDAU = .TRUE.
LDAUTYPE = 2          # Dudarev
LDAUL = 2 -1          # l quantum number (d, s/p)
LDAUU = 5.0 0.0       # U value (eV)
LDAUJ = 0.0 0.0       # J value

van der Waals Corrections

DFT-D3:

IVDW = 11             # DFT-D3 (Grimme)

vdW-DF:

GGA = MK              # optPBE-vdW
LUSE_VDW = .TRUE.
AGGAC = 0.0000

Convergence Testing Strategy

1. k-Point Convergence

# Test sequence
KPOINTS: 4x4x4, 6x6x6, 8x8x8, 10x10x10, 12x12x12

# Converged when ΔE < 1 meV/atom between successive grids

2. Energy Cutoff Convergence

# Test ENCUT
ENCUT: 400, 450, 500, 550, 600 eV

# Converged when ΔE < 1 meV/atom
# Forces may need higher cutoff

3. Systematic Approach

1. First: Converge ENCUT (fix k-points at moderate density)
2. Second: Converge k-points (use converged ENCUT)
3. Document: Save convergence test results

Smearing Methods (ISMEAR)

Recommendations:

• Metals, relaxation: ISMEAR=1, SIGMA=0.2
• Semiconductors, relaxation: ISMEAR=0, SIGMA=0.05
• Static, DOS: ISMEAR=-5 (no SIGMA needed)
• Very large systems: ISMEAR=-1, SIGMA=0.1

Common Parameter Combinations

Standard Relaxation (Metals)

# INCAR
ENCUT = 520
PREC = Accurate
IBRION = 2
ISIF = 3
NSW = 100
EDIFFG = -0.02
ISMEAR = 1
SIGMA = 0.2
ALGO = Fast
LREAL = Auto

# KPOINTS
Gamma-centered
0
Gamma
  8  8  8
  0  0  0

High-Accuracy Static Calculation

# INCAR
ENCUT = 600          # Higher cutoff
PREC = Accurate
IBRION = -1
NSW = 0
EDIFF = 1E-8         # Tight convergence
ISMEAR = -5          # Tetrahedron
ALGO = Normal
LREAL = .FALSE.      # Reciprocal space

# KPOINTS (very dense)
0
Gamma
  12 12 12
  0  0  0

Fast Testing Setup

# INCAR
ENCUT = 400          # Lower cutoff
PREC = Normal
EDIFF = 1E-4         # Loose
ISMEAR = 0
SIGMA = 0.1
ALGO = Fast
LREAL = Auto

# KPOINTS (coarse)
0
Gamma
  4  4  4
  0  0  0

Performance Optimization

Parallelization

INCAR:

NCORE = 4            # Cores per band (orbital parallelization)
# OR
NPAR = 8             # Number of groups for band parallelization
KPAR = 4             # k-point parallelization
LPLANE = .TRUE.      # Plane-wise distribution

Guidelines:

• NCORE ≈ number of cores per node / 2-4
• KPAR = number of k-points (or divisor)
• For large systems (>100 atoms): NCORE=1-4
• For many k-points: Use KPAR

Memory Management

LREAL = Auto         # Reduce memory for large systems
NCORE = 4            # Reduce memory per core

Error Handling

Common Errors and Fixes

"ZBRENT: fatal error in bracketing"

# Fix: Reduce POTIM or use different IBRION
POTIM = 0.2

"EDDDAV: X eigenvalues not converged"

# Fix: Increase NELM, change ALGO
NELM = 200
ALGO = All

"Sub-Space-Matrix is not hermitian"

# Fix: Reduce POTIM, check structure
POTIM = 0.1
SYMPREC = 1E-8

SCF not converging:

# Try sequential fixes:
1. ALGO = All
2. Increase NELM = 200
3. AMIX = 0.2, BMIX = 0.0001
4. Check initial structure (too close atoms?)

Best Practices

1. Always Converge: Test k-points and ENCUT before production runs
2. Use Symmetry: Let VASP detect symmetry (speeds up calculations)
3. Check OUTCAR: Verify "reached required accuracy" message
4. Monitor: Check OSZICAR during run for convergence
5. Save Everything: Keep all outputs (OUTCAR, vasprun.xml) for analysis
6. Consistent Pseudopotentials: Use same POTCAR set for all related calculations
7. Document Settings: Record all INCAR parameters used

Calculation Workflows

Full Relaxation → Properties

1. Relaxation: Optimize structure (ISIF=3, IBRION=2)
2. Static: Accurate energy (ISMEAR=-5, dense k-points)
3. Band Structure: Non-SCF with line-mode k-points
4. DOS: Dense k-mesh with ISMEAR=-5
5. Properties: Phonons, elastic, etc.

Convergence Testing Workflow

1. Rough optimization: Low ENCUT, coarse k-points
2. Test ENCUT: Fixed k-points, vary ENCUT
3. Test k-points: Converged ENCUT, vary k-mesh
4. Production: Use converged parameters

Subskills

Invoke specific subskills for detailed guidance:

• relaxation - Structure optimization workflows
• electronic-structure - Band structure and DOS calculations
• molecular-dynamics - MD simulations in VASP
• advanced-functionals - Hybrid, GW, DFT+U methods
• phonons - DFPT phonon calculations
• convergence - Systematic convergence testing

Quick Decision Guide

What type of calculation?

References

• VASP Manual: https://vasp.at/wiki/The_VASP_Manual
• VASP Tutorials: https://vasp.at/tutorials/latest/
• Parameter Index: https://vasp.at/wiki/index.php/Category:INCAR

See Also

• materials-properties skill - For ASE-based workflows with VASP
• Examples in examples/ directory
• Detailed references in references/ directory