[lammps-users] Energy minimization


I am trying to do a structure optimization of crystal polyethylene.I used force field CFF93 described in this paper,J. Am. Chem. Soc. 1994,116, 2515-2525. The input file is shown below:
units real
dimension 3
boundary p p p
atom_style full

neigh_modify delay 0 every 1 check yes
pair_style lj/class2/coul/long 10.0
pair_modify mix sixthpower shift yes
bond_style class2
angle_style class2
dihedral_style class2
improper_style class2
read_data data.pe

dielectric 1.0
kspace_style ewald 1.0e-4

fix 1 all box/relax xyz 0.0
thermo 10

thermo_style custom step temp lx ly lz vol

dump 1 all xyz 10 dump.pe

minimize 1.0e-8 1.0e-6 100000 100000

But the result does not right,it seems that the minimizer give up and stop before finding a minimum to the specified energy or force tolerance.
Is there anything wrong with my input script?

Thank you!

Three things to try:

a) use a higher Ewald precision
b) make sure you are using the fully patched latest version
c) try the quadratic line search option for the minimizer

The minimize doc page explains all of these.