vasp

name vasp description Expert assistant for VASP (Vienna Ab initio Simulation Package) calculations - input file generation, parameter selection, workflow setup, and best practices for accurate DFT calculations allowed-tools ["*"] VASP Calculation Setup Skill You are an expert assistant for setting up VASP (Vienna Ab initio Simulation Package) calculations. Help users generate correct input files (INCAR, POSCAR, KPOINTS, POTCAR), select optimal parameters for their calculation type, and follow best practices for accurate and efficient DFT calculations. Overview VASP is a plane-wave DFT code widely used in materials science and computational chemistry. This skill covers: Input Files: INCAR: Control parameters POSCAR: Atomic positions and lattice KPOINTS: k-point sampling POTCAR: Pseudopotentials Calculation Types: Structure relaxation Static calculations (single-point energy) Band structure and DOS Molecular dynamics Phonons and elastic properties Advanced: GW, hybrid functionals, DFPT Parameter Selection: Accuracy vs efficiency trade-offs System-specific recommendations Convergence testing strategies 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 First: Converge ENCUT (fix k-points at moderate density) Second: Converge k-points (use converged ENCUT) Document: Save convergence test results Smearing Methods (ISMEAR) ISMEAR Method Use Case -5 Tetrahedron Static calcs, DOS, accurate energies -4 Tetrahedron+Blöchl Like -5, slightly different -1 Fermi smearing Metals 0 Gaussian General purpose 1+ Methfessel-Paxton order N Relaxations, metals 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 Always Converge: Test k-points and ENCUT before production runs Use Symmetry: Let VASP detect symmetry (speeds up calculations) Check OUTCAR: Verify "reached required accuracy" message Monitor: Check OSZICAR during run for convergence Save Everything: Keep all outputs (OUTCAR, vasprun.xml) for analysis Consistent Pseudopotentials: Use same POTCAR set for all related calculations Document Settings: Record all INCAR parameters used Calculation Workflows Full Relaxation → Properties Relaxation: Optimize structure (ISIF=3, IBRION=2) Static: Accurate energy (ISMEAR=-5, dense k-points) Band Structure: Non-SCF with line-mode k-points DOS: Dense k-mesh with ISMEAR=-5 Properties: Phonons, elastic, etc. Convergence Testing Workflow Rough optimization: Low ENCUT, coarse k-points