Vasp Geometric Optimization Incar File Brief Introduction

Global Parameters System = silicon ISTART = 1 (Read existing wavefunction if there) ISPIN = 2 (Spin polarised DFT default value 1-non spin) MAGMOM = INO*1 (ISPIN=At 2 o'clock, MAGMOM=Number of atoms*1 non-linear magnetic system MAGMOM=3*number of atoms*1) # ICHARG = 11 (Non-self-consistent: GGA/LDA band structures) LREAL = .FALSE. (Projection operators: automatic) ENCUT = 400 (Cut-off energy for plane wave basis set, in eV,130% * max(ENMAX)Must be larger than the largest system element to find in the ENMAX-POTCAR file) PREC = Normal (Precision level) LWAVE = .TRUE. (Write WAVECAR or not) LCHARG = .TRUE. (Write CHGCAR or not) ADDGRID= .TRUE. (Increase grid helps GGA convergence) # LVTOT = .TRUE. (Write total electrostatic potential into LOCPOT or not) # LVHAR = .TRUE. (Write ionic + Hartree electrostatic potential into LOCPOT or not) # NELECT = (No. of electrons: charged cells be careful) # LPLANE = .TRUE. (Real space distribution supercells) # NPAR = 4 (Max is no. nodes don't set for hybrids) # NWRITE = 2 (Medium-level output) # KPAR = 2 (Divides k-grid into separate groups) # NGX = 500 (FFT grid mesh density for nice charge/potential plots) # NGY = 500 (FFT grid mesh density for nice charge/potential plots) # NGZ = 500 (FFT grid mesh density for nice charge/potential plots) Electronic Relaxation ISMEAR = 0 (Partial population-1-Fermi, 0-Gaussian metals:1phonon frequencies:1-N-Methfessel-Paxtontotal energy:-5-Blochl correctionsAvoid using ISMEAR>0 for semiconductors and insulators) SIGMA = 0.05 (Smearing value in eV metals:0.2) NELM = 60 (Max electronic SCF steps)Maximum number of electronic iteration steps 200 500 etc. NELMIN = 6 (Min electronic SCF steps)Minimum steps of electronic iteration EDIFF = 1E-08 (SCF energy convergence in eV)EDIFF control electronic step(Self-consistent)In most cases, 1E-4 is sufficient for the convergence standard, and 1E-5 is recommended. # GGA = PS (PBEsol exchange-correlation, LDA pseudopotential for GGA calculation. Default-read POTCAR, GGA = 91 or PE or RP or PS or AM) Ionic Relaxation NSW = 100 (Max ionic steps)NSW controls the number of steps in geometry optimization. That is, how many ion steps VASP performs. 100, 200 and above, depending on the architecture. IBRION = 2 (Algorithm: 0-MD Molecular Dynamics 1-Quasi-New quasi-Newton method ion relaxation-when close to the steady state structure 2-CG conjugate gradient method-commonly used 3-DMD oscillatory molecular dynamics-when the structure is very poor 5,6-Hessian matrix and phono frequencies 7,8-Density functional perturbation theory calculation derivative)This parameter determines the optimization process of the structure POTIM = 0.5 (Ion moving step IBRION=Must be set manually at 0 IBRION=1,2,3, the default is 0.5 )0.2, 0.3, 0.5, etc. ISIF = 3 (Determine the type of mobile optimization Stress/relaxation: 0-Force/relax, 1-0+total pressure, 2-stress/Ions, 3-Shape/Ions/Volume, 4-Shape/Ions, 5-Force/stress/shape, 6-no ions, 7-6-shape) EDIFFG = -2E-02 (Ionic convergence eV/AA) %% EDIFFG controls the convergence of the geometric optimization process, and stops the optimization when the structure changes before and after meet our requirements. For optimization, we can use force as the convergence criterion , EDIFFG is negative at this time. Generally speaking, the value is between -0.01 and -0.05(-0.01 is already a very strict requirement for force convergence)。 Of course, we can also use energy as a standard: at this time, EDIFFG is a positive value, generally 0.001-0.0001 %% # ISYM = 2 (Symmetry: 0=none 2=GGA 3=hybrids)