# vasp的分子动力学模拟

vasp做分子动力学的好处，由于vasp是近些年开发的比较成熟的软件，在做电子scf速度方面有较好的优势。

INCAR：
EDIFF 一般来说，用1E-4 或者1E-5都可以，这个参数只是对第一个离子步的自洽影响大一些，对于长时间的分子动力学的模拟，精度小一点也无所谓，但不能太小。
IBRION=0 分子动力学模拟
IALGO=48 一般用48，对于原子数较多，这个优化方式较好。
NSW=1000 多少个时间步长。
POTIM=3 时间步长,单位fs, 通常1到3.
ISIF=2 计算外界的压力.
NBLOCK= 1 多少个时间步长，写一次CONTCAR，CHG和CHGCAR，PCDAT.
KBLOCK=50 NBLOCK*KBLOCK 个步长写一次 XDATCAR.
ISMEAR=-1 费米迪拉克分布.
SIGMA =0.05 单位:电子伏
NELMIN=8 一般用6到8, 最小的电子scf数.太少的话,收敛的不好.
LREAL=A
APACO=10 径向分布函数距离, 单位是埃.
NPACO=200 径向分布函数插的点数.
LCHARG=F 尽量不写电荷密度,否则CHG文件太大.
TEBEG=300 初始温度.
TEEND=300 终态温度。 不设的话，等于TEBEG.
SMASS -3 NVE ensemble;-1 用来做模拟退火。大于0 NVT 系综。

(http://cms.mpi.univie.ac.at/vasp/vasp/node95.html#incar)

This file determines the kind of job which VASP will perform; single point energy calculation (SPE), geometry

optimisation (GO - coarse/fine), molecular dynamics (MD - nve/nvt), spin polarised calculation (mag).

Examples can

be found in /home/cs/model/vasp_util.

Example; INCAR.spe

$system = single point energy calc NELMIN = 4 minimum number of electronic SCF cycles EDIFF = 1E-6 stooping criterion for electronic convergence NSW = 0 number of ionic shifts ISMEAR = 0 treatment of partial occupancies of electronic levels Example; INCAR.coarse$system = coarse geom optimisation

NELMIN = 4

EDIFF = 1E-2

EDIFFG = -1E-2 stopping criterion for forces Fmax < 0.01 eV/A

IBRION = 2 minimisation method, good away from minimum

ISIF = 3 optimise coords and cell pars

LREAL =.TRUE. do calc in real space - quicker

NSW = 20 maximum of 20 ionic shifts

ISMEAR = 0

LCHARG =.FALSE. don't write CHG and CHGCAR files

Example; INCAR.fine

$system = geom optimisation NELMIN = 4 EDIFF = 1E-6 EDIFFG = -1E-4 PREC = high increase energy cut-off by 25% IBRION = 1 minimisation method, good close to minimum ISIF = 3 NSW = 50 ISMEAR = 0 LCHARG=.FALSE. Example; INCAR.mag$system = collinear mag structure calc

IBRION = 1

ISIF = 3

NPAR = 1 forces mag structure to be written in output file

EDIFF = 1E-6

EDIFFG = -1E-3

PREC = high

RWIGS = 1.376 0.900 1.233 1.302 radii for spherical integration of spin density, 1 per atom

ISPIN = 2 do spin polarised calc

MAGMOM = 24*0 5 -5 -5 5 initial mag moments for 28 atoms

NSW = 20

Example; INCAR.nve

$system = molecular dynamics ALGO = V MAXMIX = 40 IBRION = 0 do molecular dynamics NSW = 6000 number of time steps NBLOCK = 1 store structure every time step POTIM = 3.0 time step 3fs TEBEG = 673 target temperature ISYM = 0 turn off symmetry SMASS = -3 NVE ensemble LREAL =.TRUE. LCHARG =.FALSE. NELMIN = 4 PREC = LOW reduce energy cut-off by 25% for MD ISTART = 0 ISMEAR = 0; SIGMA=0.1 Example; INCAR.nvt$system = molecular dynamics

ALGO = V

MAXMIX = 40

IBRION = 0

NSW = 6000

NBLOCK = 1

POTIM = 3.0

TEBEG = 673

ISYM = 0

SMASS = 2 NVT ensemble, value determines frequency of coupling to heat bath

LREAL =.TRUE.

LCHARG =.FALSE.

NELMIN = 4

PREC = LOW

ISTART = 0

ISMEAR = 0; SIGMA=0.1

Example; INCAR.scale

\$system = molecular dynamics quench

ALGO = V

MAXMIX = 40

IBRION = 0

NSW = 50

NBLOCK = 5 rescale temperature every 5 steps

POTIM = 3.0

TEBEG = 683 initial temp

TEEND = 673 final temp

ISYM = 0

SMASS = -1 MD with velocity scaling

LREAL =.TRUE.

LCHARG =.FALSE.

NELMIN = 4

PREC = LOW

ISTART = 0

ISMEAR = 0; SIGMA=0.1

https://blog.sciencenet.cn/blog-671981-612445.html

## 全部精选博文导读

GMT+8, 2024-9-17 04:30