hiMihail here is the input file
input file for polymer nanocomposite
units lj
atom_style full
neighbor 0.36 bin
neigh_modify delay 10
pair_style lj/cut 1.12246
bond_style fene
read_data …/data.ncomp
timestep 0.005
pair_coeff 1 1 1.0 1.0 1.12246
pair_coeff 2 2 1.0 1.0 1.12246
pair_coeff 1 2 1.0 1.0 2.5
bond_coeff 1 30.0 1.5 1.0 1.0
thermo_style custom step eng pe ke temp press
thermo 10
fix 1 all nvt 1.0 1.0 1.0
dump 2 all custom 1000 ncomp.trj tag type x y z
dump_modify 2 format “%5d %5d %8.4f %8.4f %8.4f”
run 100000
thanks
venkat
I’m don’t know what is going on. If you have only one bond type with these parameters LAMMPS should not complain about a bond distance of around 1.0 as it does. It seems to me the bond potential does not have the right R0 and I dont see why (I assume the Bond section in the input file is correctly written…)
Try to put “bond_coeff * 30.0 1.5 1.0 1.0” in the input script.
If it still does not work make LAMMPS print the bond potential parameters adding a line or two in the bond_fene.cpp file around the error message to see what exactly goes wrong.
hope this works
Mihail
If it still does not work make LAMMPS print the bond potential parameters
adding a line or two in the bond_fene.cpp file around the error message to
see what exactly goes wrong.
These are the relevant lines from bond_fene.cpp:
rlogarg = 1.0 - rsq/r0sq;
// if r -> r0, then rlogarg < 0.0 which is an error
// issue a warning and reset rlogarg = epsilon
// if r > 2*r0 something serious is wrong, abort
if (rlogarg < 0.1) {
char str[128];
sprintf(str,"FENE bond too long: %d %d %d %g",
update->ntimestep,atom->tag[i1],atom->tag[i2],sqrt(rsq));
error->warning(str);
if (rlogarg <= -3.0) error->one("Bad FENE bond");
rlogarg = 0.1;
}
Like Mihail, I don't see why LAMMPS would complain if
r = 0.98 and r0 = 1.5, as it appears to from your emails.
Why don't you add some more quantities to the sprintf(), like
r0 and rlogarg, i1 and i2, the coords of those 2 atoms, etc and
see if it all makes sense and matches your input data file.
Steve