24小时热门版块排行榜

返回列表

当前只显示满足指定条件的回帖，点击这里查看本话题的所有回帖

Mayerss

新虫 (小有名气)

应助: 0 (幼儿园)
金币: 115
帖子: 63
在线: 22小时
虫号: 3218673
注册: 2014-05-19
专业: 工程热物理相关交叉领域

[求助] 关于Green-Kubo方法模拟水的粘度已有3人参与

求问有没有大神用lammps做过水的模拟？
我现在改编了一下manual里面计算液氩粘度的那个算例，来模拟水的粘度，300k下得到的结果是0.2mPa.s，查得的标准值是0.8mPa.s，请路过的大神帮忙看一下是哪里出了问题，多谢！

in文件贴在下面，data文件和log文件在附件中。

#  LAMMPS input script for viscosity of purewater

units       real
variable    T equal 300
variable    V equal vol
variable    dt equal 0.4
variable    p equal 400 # correlation length
variable    s equal 5 # sample interval
variable    d equal $p*$s # dump interval

# convert from LAMMPS real units to SI

variable    kB equal 1.3806504e-23 # [J/K/ Boltzmann
variable    atm2Pa equal 101325.0
variable    A2m equal 1.0e-10
variable    fs2s equal 1.0e-15
variable    convert equal ${atm2Pa}*${atm2Pa}*${fs2s}*${A2m}*${A2m}*${A2m}

# setup problem

dimension    3
boundary    p p p
atom_style    full
bond_style    harmonic
angle_style harmonic

pair_style    lj/cut/tip4p/long 1 2 1 1 0.125 12 15
kspace_style pppm/tip4p 1e-6
read_data    sketch.data

pair_coeff  1 2  0.0 0.0 # O-H
pair_coeff  2 2  0.0 0.0 # H-H
pair_coeff  1 1  0.16275 3.16435 # O-O

timestep    ${dt}
thermo       $d

# equilibration and thermalization

velocity    all create $T 102486 mom yes rot yes dist gaussian
fix          NVT all nvt temp $T $T 40 drag 0.2
run          100000

# viscosity calculation, switch to NVE if desired

#unfix       NVT
#fix          NVE all nve

reset_timestep 0
variable    pxy equal pxy
variable    pxz equal pxz
variable    pyz equal pyz
fix          SS all ave/correlate $s $p $d &
            v_pxy v_pxz v_pyz type auto file S0St.dat ave running
variable    scale equal ${convert}/(${kB}*$T)*$V*$s*${dt}
variable    v11 equal trap(f_SS[3])*${scale}
variable    v22 equal trap(f_SS[4])*${scale}
variable    v33 equal trap(f_SS[5])*${scale}
thermo_style custom step temp press v_pxy v_pxz v_pyz v_v11 v_v22 v_v33
run          200000
variable    v equal (v_v11+v_v22+v_v33)/3.0
variable    ndens equal count(all)/vol
print       "average viscosity: $v [Pa.s/ @ $T K, ${ndens} /A^3"

回复此楼