Total energy not conservative under NVE

Hi all,

I have a problem when I tried to do NVE simulation in an organic system. From the manual, the total energy should be conservative under NVE, however in our case the total energy fluctuation was about 50~80kcal/mol for the system contains 98 atoms (two chains, each chain contains 5-ring thiophene with a –C3H6COOH group attached to it’s tail ). We also did tests such as more atoms and smaller tiemsteps, but there’s no apparent improvement. Follows are the main commands


units real

dimension 3

atom_style full

pair_style lj/class2/coul/long 10.0

bond_style class2

angle_style class2

dihedral_style class2

improper_style class2

boundary p p p

kspace_style ewald 1E-05

atom definition

read_data struct2.lammps05


neighbor 2.0 bin

neigh_modify delay 0 every 1 check yes

timestep 1.0

min_style cg

neigh_modify every 2 delay 10 check yes one 10000 page 100000

run_style verlet

thermo 1

thermo_style custom step etotal temp pe ke

dump mydump all atom 1 dump.out

minimize 1.0e-11 1.0e-12 5000 10000

velocity all create 230 4928459 dist gaussian

fix 1 all nve

run 100000

unfix 1

We thanks very much for any suggestions!



You're cutting off the Vdwl interaction, so I wouldn't
expect perfect energy conservation, just stability over time.
Did you try shifting the potential or using a tail correction?


Hi Steve,

Tnanks very much for your reply. I will do some tests under your suggestions. Thanks again.