themostatting wall in a couette shear flow

Hello all,

I have read couple of emails existing in the mailing list on the topic of thermostatting rigid walls. I haven’t yet been able to summarize the proper method for my purpose. I want to simulate the couette flow of water confined between two sliding rigid walls. I want to thermostat wall atoms at 300 K and let the generated viscous heat in the fluid be conducted out through the walls. This is what being recommended in the literature as opposed to thermostatting the fluid, since the former method resembles more the actual rheological experiments.

Before applying Couette flow, I first equilibrated the system. I used the “fix spring/self” to let wall atoms fluctuate around their initial position and then used “fix langevin” to thermostat walls. This is what being recommended in the mailing list. However, I get the following error:

Step PotEng TotEng Press Temp temp_wat temp_wal
0 -47396.54 -47396.54 176691.6 0 0 0
1 -97958.228 -nan -nan -nan -nan 14537232
ERROR on proc 0: Out of range atoms - cannot compute PPPM (…/pppm.cpp:1904)

Could anyone please give me any advice as how to solve this problem?

Regards,

Farshad

PS. My input file is as follows:

units metal
dimension 3
boundary p p p
atom_style full

read geometry

read_data mixed-waterslab.dat
neighbor 3.0 bin
neigh_modify delay 0 every 10 check yes

set potential function and parameters

Create Groups

group hy type 5 # H_water
group ox type 6 # O_water
set group ox charge -0.8476
set group hy charge 0.4238

pair_style hybrid/overlay rebo lj/cut 7.5 lj/cut/coul/long 8.5
pair_coeff * * rebo CH.airebo C H C H NULL NULL
pair_coeff * * lj/cut 0.0 0.0
pair_coeff * * lj/cut/coul/long 0.0 0.0
pair_coeff 1 6 lj/cut 0.013 2.71
pair_coeff 2 6 lj/cut 0.0036 1.7753

pair_coeff 3 6 lj/cut 0.013 2.71

pair_coeff 4 6 lj/cut 0.0036 1.7753

pair_coeff 6 6 lj/cut/coul/long 0.0067 3.166

bond_style harmonic
bond_coeff 1 7.669 1.0

angle_style harmonic
angle_coeff 1 1.829 109.47
kspace_style pppm 1.0e-5 #final npt relaxation

group water type 5 6 # water
group slab type 1 2 3 4 # slab
compute temp_water water temp
compute temp_wall slab temp
thermo 1
thermo_style custom step pe etotal press temp c_temp_water c_temp_wall

timestep 0.001

fix tether slab spring/self 3.0
fix NVE all nve
fix WTEMP slab langevin 10.0 150.0 0.1 786467
fix shake_1 water shake 1e-5 20 0 b 1 a 1

dump dcd_1 all dcd 500 equil_10K_150K.dcd
run 30000
write_restart restart.equil_10K_150K.*
unfix WTEMP
unfix shake_1
undump dcd_1
fix WTEMP slab langevin 150.0 298.0 0.1 786467
fix shake_2 water shake 1e-5 20 0 b 1 a 1
dump dcd_2 all dcd 500 equil_150K_298K.dcd
run 30000
write_restart restart.equil_150K_298K.*
unfix WTEMP
unfix shake_2
undump dcd_2
fix WTEMP slab langevin 298.0 298.0 0.1 786467
fix shake_3 water shake 1e-5 20 0 b 1 a 1
dump dcd_3 all dcd 500 equil_nvt_298K.dcd
run 40000
write_restart restart.equil_nvt_298K.*
unfix WTEMP
unfix shake_3
undump dcd_3

ERROR on proc 0: Out of range atoms - cannot compute PPPM (…/pppm.cpp:1904)
Could anyone please give me any advice as how to solve this problem?

This error and question comes up often. Please read the manual
which explains it (doc/Section_errors.html), and search the mail
list if you have further Qs.

Steve