VASP(1)_参数测试_K点测试

KPOINTS 或 KSPACING 测试

必要输入文件：

k_test.sh
POTCAR
INCAR和POSCAR可在k_test.sh中设置，也可独立给出

脚本1(k_test.sh): KPOINTS测试

#!/bin/bash

#生成vasp静态计算的INCAR
cat > INCAR_static <<!
Global Parameters
  ISTART =  0            (Read existing wavefunction; if there)
  ICHARG =  2            (Non-self-consistent: GGA/LDA band structures)
  LREAL  = .FALSE.       (Projection operators: automatic)
  ENCUT  =  500           (Cut-off energy for plane wave basis set, in eV)
  PREC   =  Accurate     (Precision level)  
  LWAVE  = .FALSE.       (Write WAVECAR or not)
  LCHARG = .FALSE.       (Write CHGCAR or not) 
  ADDGRID= .TRUE.        (Increase grid; helps GGA convergence)

Electronic Relaxation
  ISMEAR =  -5           (Gaussian smearing; metals:1)
  #SIGMA  =  0.05        (Smearing value in eV; metals:0.2)
  NELM   =  60           (Max electronic SCF steps)  
  NELMIN =  4            (Min electronic SCF steps)
  EDIFF  =  1E-06        (SCF energy convergence; in eV)
  GGA  =  PE             (PBEsol exchange-correlation)

Ionic Relaxation
  ISIF   =  2            (Stress/relaxation: 2-Ions, 3-Shape/Ions/V，4-Shape/Ions)
  EDIFFG = -0.001        (Ionic convergence; eV/AA)
  KSPACING = 0.10
!

cp INCAR_static INCAR

#产生计算所需POSCAR
cat > POSCAR<<!
Si8
1.0000000000
    5.4687280000        0.0000000000        0.0000000000
    0.0000000000        5.4687280000        0.0000000000
    0.0000000000        0.0000000000        5.4687280000
Si
8
Direct
    0.0000000000        0.0000000000        0.0000000000
    0.2500000000        0.7500000000        0.7500000000
    0.5000000000        0.0000000000        0.5000000000
    0.0000000000        0.5000000000        0.5000000000
    0.5000000000        0.5000000000        0.0000000000
    0.7500000000        0.2500000000        0.7500000000
    0.7500000000        0.7500000000        0.2500000000
    0.2500000000        0.2500000000        0.2500000000
!


for i in $(seq 6 3 15) #K点从6-24，步数为3
do

#生成KPOINTS文件，K点类型：Monkhorst-Pack (M) 或者 Gamma (G)
cat > KPOINTS <<!
Automatic mesh
0
Monkhorst-Pack
$i $i $i
0  0  0
!

echo "KPOINTS = $i" ; time mpirun -n 16 vasp_std #vasp并行运行命令，根据系统自行修改

rm KPOINTS
#提取计算得到的能量
E=$(grep "TOTEN" OUTCAR | tail -1 | awk '{printf "%12.9f \n", $5 }')
echo $i $E >>kpoints_energy.out
done

提交脚本任务运行，成功结束后可以得到输出文件kpoints_enengy.out
可以使用OriginPro等画图工具画出kpoints-能量关系

Si的KPOINTS测试

根据收敛性，大概选择KPOINTS为$9\times9\times9$9×9×9

脚本2(k_test.sh): KSPACING测试

#!/bin/bash

#产生计算所需POSCAR
cat > POSCAR<<!
Si8
1.0000000000
    5.4687280000        0.0000000000        0.0000000000
    0.0000000000        5.4687280000        0.0000000000
    0.0000000000        0.0000000000        5.4687280000
Si
8
Direct
    0.0000000000        0.0000000000        0.0000000000
    0.2500000000        0.7500000000        0.7500000000
    0.5000000000        0.0000000000        0.5000000000
    0.0000000000        0.5000000000        0.5000000000
    0.5000000000        0.5000000000        0.0000000000
    0.7500000000        0.2500000000        0.7500000000
    0.7500000000        0.7500000000        0.2500000000
    0.2500000000        0.2500000000        0.2500000000
!

for i in $(seq 0.5 -0.05 0.1) #K点密度从0.5-0.1，步数为0.05
do

#生成vasp静态计算的INCAR
cat > INCAR_static <<!
Global Parameters
  ISTART =  0            (Read existing wavefunction; if there)
  ICHARG =  2            (Non-self-consistent: GGA/LDA band structures)
  LREAL  = .FALSE.       (Projection operators: automatic)
  ENCUT  =  500           (Cut-off energy for plane wave basis set, in eV)
  PREC   =  Accurate     (Precision level)  
  LWAVE  = .FALSE.       (Write WAVECAR or not)
  LCHARG = .FALSE.       (Write CHGCAR or not) 
  ADDGRID= .TRUE.        (Increase grid; helps GGA convergence)

Electronic Relaxation
  ISMEAR =  -5           (Gaussian smearing; metals:1)
  #SIGMA  =  0.05        (Smearing value in eV; metals:0.2)
  NELM   =  60           (Max electronic SCF steps)  
  NELMIN =  4            (Min electronic SCF steps)
  EDIFF  =  1E-06        (SCF energy convergence; in eV)
  GGA  =  PE             (PBEsol exchange-correlation)

Ionic Relaxation
  ISIF   =  2            (Stress/relaxation: 2-Ions, 3-Shape/Ions/V，4-Shape/Ions)
  EDIFFG = -0.001        (Ionic convergence; eV/AA)
  KSPACING = $i 
  KGAMMA = .FALSE.       #(true: GAMMA; false: Monkhorst-Pack )
!

cp INCAR_static INCAR
echo "KPOINTS = $i" ; time mpirun -n 16 vasp_std #vasp并行运行命令，根据系统自行修改

rm INCAR_static
rm INCAR
#提取计算得到的能量
E=$(grep "TOTEN" OUTCAR | tail -1 | awk '{printf "%12.9f \n", $5 }')
echo $i $E >>kspace_energy.out
done

注：Auto mesh模式下。 $KPONITSnumber = max(1,|\vec{b}|/(2\pi\times{KSPACING}))$KPONITSnumber=max(1,∣b∣/(2π×KSPACING))
另外，后续介绍中，主要使用的是KPOINTS文件，KSPACING可以根据自行需要选择使用。

提交脚本任务运行，成功结束后可以得到输出文件kspace_enengy.out
可以使用OriginPro等画图工具画出k点密度-能量关系。

Si的KSPACE测试

根据能量收敛判断，选择K点密度为0.15较为合适。