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[lammps-users] Temperature and Energy increases with "nve/limit" command
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[lammps-users] Temperature and Energy increases with "nve/limit" command


From: surendra jain <jainsk.iitkgp@...24...>
Date: Sat, 5 Aug 2017 11:10:21 +0530

Dear Lammps users,

  I am working on dynamics of fluids in carbon models. The carbon
model remains fixed during simulation. I am using "NVE/limit 0.05" for
 the fluid molecules for equilibration and to remove any high energy
configurations. However, the temperature and energy (both KE and PE)
increase during the simulation.

I am attaching the input script . Any help will be appreciated.

-----------------------------------------------------------------------------------

dimension       3
units           real
boundary        p p p

kspace_style    pppm 1.0e-4
kspace_modify   order 3
atom_style      full
pair_style      lj/cut/coul/long 10.0 12.0
bond_style      harmonic
angle_style     harmonic
pair_modify     mix arithmetic


read_data       lammps_data.dat

pair_coeff      * *  0.0      0.0
pair_coeff      1 8  0.0546   3.08
pair_coeff      2 8  0.00     1.4
pair_coeff      3 8  0.0744   3.275
pair_coeff      4 8  0.00     1.4
pair_coeff      5 8  0.106    2.88
pair_coeff      6 8  0.0955   2.9
pair_coeff      7 8  0.04     2.610

pair_coeff      1 9  0.0934   3.205
pair_coeff      2 9  0.00     1.525
pair_coeff      3 9  0.127    3.4
pair_coeff      4 9  0.00     1.525
pair_coeff      5 9  0.181    3.005
pair_coeff      6 9  0.163    3.025
pair_coeff      7 9  0.0685   2.735

pair_coeff      8 8  0.053654  2.8
pair_coeff      8 9  0.0917    2.925
pair_coeff      9 9  0.1569    3.05


group   matrix type 1 2 3 4 5 6 7
group   fluid type 8 9


neighbor   2.0  bin
neigh_modify    delay 0 every 1 check yes
neigh_modify   exclude molecule fluid

fix             11 matrix setforce 0.0 0.0 0.0
fix             1 fluid nve/limit 0.05
compute          mytemp fluid temp

timestep        0.050

thermo_style    custom  step c_mytemp pe ke fmax evdwl ecoul  epair
ebond eangle elong etail
thermo          10
run             100000
unfix 1

fix             22 fluid nve
fix             2  fluid langevin 100.0 100.0 100.0 498094

thermo      10
run         100000

unfix 2
fix             29  fluid langevin 300.0 300.0 100.0 498094

reset_timestep  0

compute     2 fluid vacf
fix        14 fluid ave/time 1 1 1 c_2[4] file tmp.vacf
fix         5 fluid vector 1 c_2[4]
variable    diff equal dt*trap(f_5)

compute          CCRDF all rdf 200  8 8
fix              3 all ave/time 100 1 1000 c_CCRDF[*] file cc.rdf mode vector
compute          CMRDF all rdf 200  1 8
fix             32 all ave/time 100 1 1000 c_CMRDF[*] file cm.rdf mode vector

compute         13 fluid msd com yes
variable        twopoint equal c_13[4]/4/(step*dt+1.0e-6)
fix             9 all vector 10 c_13[4]
variable        fitslope equal slope(f_9)/4/(10*dt)


thermo_style    custom step temp pe ke etotal fmax c_13[4] c_mytemp
evdwl ecoul  epair ebond eangle elong etail

restart         10000 temp.restart

dump            108 all xyz 10 tmp.xyz
dump            109 fluid custom 10 tmp5.xyz id mol type xu yu zu ix iy iz
dump            110 fluid custom 10 tmp6.xyz id mol type x y z
dump            311 fluid custom 10 tmp7.xyz id mol type xu yu zu

timestep        0.05

thermo          10
run             100000

-----------------------------------------------------------------------------------

Best Regards,
Surendra