Here is my first mail, it may answer most of your questions. I use Forcite Module with Atom based VdW calculations with a 15 A cut off.
Thanks for your response.
I use Materials Studio and LAMMPS simultaneously for a polyimide.
The problem i have is that, while MS Forcite module calculates my structure’s VdW energy as -78.516, in LAMMPS i have -88.7126.
I have checked my pair parameters for so many times and there are no problems in them.
I use pcff as force-field and my input file looks like;
boundary p p p
pair_style lj/class2/coul/long 15
kspace_style ewald 1.0e-004
special_bonds lj 0.0 0.0 1.0 coul 0.0 0.0 1.0
neighbor 2.0 bin
neigh_modify every 1 delay 2 check yes page 100000000 one 100000
velocity all create 308.0 4928459 rot yes dist gaussian
dump 1 all custom 100000 6fdadam760.lammpstrj id type xs ys zs ix iy iz
restart 100000 stblypn.restart
fix 1 all npt temp 308 308 20 iso 1 1 1000.0
I look at the VdW value at step 0.
I suspect that this may be due to the long range VdW truncations, yet could not find a solution for it.