Hi. I am trying to use fix_deform to strain a system at constant volume, as was done by the old fix_uniaxial. The key part of my script is
pair_style lj/cut 2.5
pair_modify shift yes
pair_coeff 1 1 1.0 1.0 2.5
fix 1 all nve
fix 2 all langevin 1 1 1 1299709
fix 3 all deform 1 x erate .001 y volume z volume
thermo_style custom step temp epair ebond pxx pyy pzz lx ly lz
timestep .01
thermo 100
restart 10000 extend.res
run 50
Then, when I run LAMMPS, I get the following error.
LAMMPS (22 Jun 2007)
Reading restart file ...
orthogonal box = (-11.3768 -11.3768 -11.3768) to (11.3768 11.3768 11.3768)
1 by 1 by 1 processor grid
10013 atoms
478686 bonds
Finding 1-2 1-3 1-4 neighbors ...
969 = max # of 1-2 neighbors
969 = max # of special neighbors
Setting up run ...
Memory usage per processor = 255.132 Mbytes
Step Temp E_pair E_mol TotEng Press Volume
0 1.0062064 -2.66439 -2.4201556 -3.5753867 -0.30668561 11780.137
ERROR: Cannot use neighbor bins - box size << cutoff
This is confusing, since the box size (~22.75) is much larger than the cutoff (2.5). The small strain I am trying to apply to the system, .0005, does not change this. I also tried replacing the ".001" in fix_deform with "0", so the fix should not do anything, but got the same error. However, when I commented out the fix deform command, the simulation ran fine.
Thoughts?
Thanks,
Rob