VASP几何优化INCAR文件简单介绍

Global Parameters
System = silicon
ISTART =  1            (Read existing wavefunction; if there)
ISPIN =  2             (Spin polarised DFT默认值1-non spin)
MAGMOM = INO*1         (ISPIN=2时，MAGMOM=原子个数*1；非线性磁性系统MAGMOM=3*原子个数*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)必须大于体系元素最大的ENMAX-POTCAR文件里查找)
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            (部居数-1-Fermi, 0-Gaussian; metals:1;phonon frequencies:1-N-Methfessel-Paxton;total energy:-5-Blochl corrections;Avoid using ISMEAR>0 for semiconductors and insulators)
SIGMA  =  0.05         (Smearing value in eV; metals:0.2)
NELM   =  60           (Max electronic SCF steps)电子迭代最大步数200 500 等等
NELMIN =  6            (Min electronic SCF steps)电子迭代最小步数
EDIFF  =  1E-08        (SCF energy convergence; in eV)EDIFF 控制电子步(自洽)的收敛标准，在大多数的情况下,1E-4足以胜任,建议1E-5即可。
# GGA  =  PS           (PBEsol exchange-correlation,LDA的赝势进行GGA计算。默认-读取POTCAR，GGA = 91或 PE 或 RP或 PS或 AM)

Ionic Relaxation
NSW    =  100          (Max ionic steps)NSW 控制几何结构优化的步数。也就是VASP进行多少离子步。100、200及以上，视体系结构。
IBRION =  2            (Algorithm: 0-MD分子动力学; 1-Quasi-New准牛顿法离子弛豫-接近稳态结构时; 2-CG共轭梯度法-常用; 3-DMD振荡分子动力学-结构非常差时; 5,6-Hessian matrix and phono frequencies; 7,8-密度泛函微扰理论计算导数)这个参数决定了结构的优化过程
POTIM  =  0.5          (离子移动步距 IBRION=0时必须手动设置; IBRION=1,2,3时，默认0.5 )0.2, 0.3 ,0.5等等 
ISIF   =  3            (决定移动优化的种类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 控制几何优化过程的收敛情况,当结构前后变化达到我们的要求时,便停止优化。对于优化,我们可以使用力作为收敛标准
,此时EDIFFG为负值。一般来说取值在-0.01到-0.05之间(-0.01对于力收敛来说已经是一个很严格的要求了)。
当然,我们也可以使用能量作为标准:此时,EDIFFG 为正值,一般为0.001-0.0001
%%
# ISYM =  2            (Symmetry: 0=none; 2=GGA; 3=hybrids)