calculating thermal conductivity for liquids

Dear All,

I used to work with Fortran version of Lammps to solve some simple flow problems
in the past, including flow between two FCC walls. I applied fix setforce 0 0 0
for the walls and Langevin thermostat for fluid. The outcome fluid properties,
density/temperature distributions,.. even viscosity were all correct.

I am trying to calculate thermal conductivity of liquid Argon using the C
version. I tried some of the examples provided in Lammps document to calculate
the thermal conductivity for Solid Argon using Green-Kubo method. Now any time I
use my old data file with \ro_wall=2*\ro_fluid, \ro_flui=0.8 (system size
50\sigma*5\sigma*17\sigma), my wall atoms escape the simulation box (z
direction) followed by liquid. I know there is something wrong with my
equilibration process. Could you point out my mistakes, and let me how a correct
input script should look like for successful calculation of thermal conductivity
using first two methods mentioned in the Lammps documentation.

any suggestion is greatly appreciated,
rea

My input script:

# 3-d LJ flow simulation

dimension 3
boundary p p f

atom_style atomic
neighbor 0.3 nsq
neigh_modify delay 5

read_data data_atoms.dat

group liquid type 1
group solidlow type 2
group solidhigh type 3

mass 1 1.0
mass 2 1.0
mass 3 1.0

# LJ potentials

pair_style lj/cut 1.12246
pair_coeff * * 1.0 1.0 1.12246

# velocity liquid create 1.5 123456 mom yes rot yes dist gaussian
# velocity solidlow create 2.0 123457 mom yes rot yes dist gaussian
# velocity solidhigh create 1.0 123458 mom yes rot yes dist gaussian

# fix 2 solidlow nvt temp 2.0 2.0 10 drag 0.2
# fix 3 solidhigh nvt temp 1.0 1.0 10 drag 0.2
# fix 1 liquid nve

fix 4 all nve
fix 5 solidlow setforce 0.0 0.0 0.0
fix 6 solidhigh setforce 0.0 0.0 0.0

dump myDump all custom 1000 dump.atom id type x y z

run 100000

Dear All,

I used to work with Fortran version of Lammps to solve some simple flow problems
in the past, including flow between two FCC walls. I applied fix setforce 0 0 0
for the walls and Langevin thermostat for fluid. The outcome fluid properties,
density/temperature distributions,.. even viscosity were all correct.

I am trying to calculate thermal conductivity of liquid Argon using the C
version. I tried some of the examples provided in Lammps document to calculate
the thermal conductivity for Solid Argon using Green-Kubo method. Now any time I
use my old data file with \ro_wall=2*\ro_fluid, \ro_flui=0.8 (system size
50\sigma*5\sigma*17\sigma), my wall atoms escape the simulation box (z
direction) followed by liquid. I know there is something wrong with my
equilibration process. Could you point out my mistakes, and let me how a correct
input script should look like for successful calculation of thermal conductivity
using first two methods mentioned in the Lammps documentation.

try running fix nve only on the group liquid
or initialize the velocities for the two solid
groups to zero. that should keep the wall atoms in place.

axel.