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)
PREC  =  Normal      (Precision level)
LWAVE  = .TRUE.        (Write WAVECAR or not)
LCHARG = .TRUE.        (Write CHGCAR or not)
ADDGRID= .TRUE.        (Increase grid; helps GGA convergence)
polarised# 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 ISM EAR>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/stre ss/shape, 6-no ions, 7-6-shape)
EDIFFG = -2E-02        (Ionic convergence; eV/AA)
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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
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# ISYM =  2            (Symmetry: 0=none; 2=GGA; 3=hybrids)

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