Dear Lammps users ,
Greetings .
i am trying to get an equilibrated system that has a molecule ( I call it " A " ) inside of around 1000 SPC water molecules .
Unfortunately the pressure more time is negative with big fluctuation .
I checked the lammps mail archive but It could not help me .
I will be grateful if you can let me know what the problem is .
This is a part of my input file :
group A type 1
group SPC type 2 3
thermo 100
fix 1 all shake 0.0001 10 100 a 3 b 2
fix 2 A setforce 0 0.0 0.0
velocity SPC create 1000.0 12345689 dist uniform
thermo_style multi
#-Energy Equilibration---------------------------------------------------
reset_timestep 0
fix 3 all nve
fix 4 all temp/rescale 10 300.0 300.0 1.0 0.5
dump 1 all custom 5000 dump.equilibrate.* id type x y z
run 100000
unfix 3
unfix 4
#-Pressure equilibration ----------------------------------------
fix 5 all npt temp 300.0 300.0 100.0 iso 1.0 1.0 100.0
##################### a part of my results :
SHAKE stats (type/ave/delta) on step 98800
2 1 1.08445e-06 9600
3 109.47 8.78948e-05
---------------- Step 98800 ----- CPU = 4381.3822 (sec) ----------------
TotEng = -13251.5328 KinEng = 2921.1675 Temp = 300.7030
PotEng = -16172.7003 E_bond = 61.3090 E_angle = 0.3973
E_dihed = 160.5680 E_impro = 0.0000 E_vdwl = 3151.6636
E_coul = 58629.4088 E_long = -78176.0471 Press = -375.5735
SHAKE stats (type/ave/delta) on step 98900
2 1 1.17644e-06 9600
3 109.47 8.65054e-05
---------------- Step 98900 ----- CPU = 4385.9652 (sec) ----------------
TotEng = -13336.6735 KinEng = 2912.1722 Temp = 299.7771
PotEng = -16248.8457 E_bond = 61.3090 E_angle = 0.3973
E_dihed = 160.5680 E_impro = 0.0000 E_vdwl = 3088.2252
E_coul = 58614.1221 E_long = -78173.4673 Press = -497.7609
SHAKE stats (type/ave/delta) on step 99000
2 1 1.0725e-06 9600
3 109.47 8.50438e-05
---------------- Step 99000 ----- CPU = 4390.5032 (sec) ----------------
TotEng = -13368.4105 KinEng = 2905.0340 Temp = 299.0423
PotEng = -16273.4445 E_bond = 61.3090 E_angle = 0.3973
E_dihed = 160.5680 E_impro = 0.0000 E_vdwl = 3042.5168
E_coul = 58631.3294 E_long = -78169.5651 Press = -540.4235
SHAKE stats (type/ave/delta) on step 99100
2 1 1.01246e-06 9600
3 109.47 0.000101034
---------------- Step 99100 ----- CPU = 4394.7845 (sec) ----------------
TotEng = -13388.2428 KinEng = 2935.1475 Temp = 302.1421
PotEng = -16323.3902 E_bond = 61.3090 E_angle = 0.3973
E_dihed = 160.5680 E_impro = 0.0000 E_vdwl = 3106.3059
E_coul = 58512.6608 E_long = -78164.6313 Press = -492.4609
Thanks for your attention.
Regards
Saeed.