Stefania,
Please send to the LAMMPS mailing list not to me, thanks.
Dear Dr. Ray,
I have a problem to run this calculation (Urea) with LAMMPS
Urea_NVT
variable f index Urea_NVT
units real
atom_style charge
boundary p p p
neighbor 2.5 bin
neigh_modify every 10 delay 0 check no
# read restart from geometry optimization
read_restart Urea.rst
pair_style reax 6.0 1 0 0.0000001
pair_coeff * * ffield.reax 1 2 3 4
I recommend you use reax/c that is faster and more flexible and reliable.
group mobile union all
velocity mobile create 800 1330944125 mom yes rot yes dist gaussian
timestep 0.01
A time step size of 0.01 fs is somewhat too small.
fix 1 mobile nvt temp 500 500 50
Your tdamp constant should be approximately 100 times the time step size.
fix rffbonds all reax/bonds 100 $f.bonds
dump 1 all atom 100 $f.dump
dump_modify 1 scale no image yes
compute reax1 all pair reax
thermo_style custom etotal ke pe temp
thermo_modify line multi
thermo 10
thermo_modify flush yes
restart 1 $f_a.rst $f_b.rst
run 100000
write_restart $f.rst
I want to run this calculation at 500K, but when I look the output file with MAPS (attached) I think that I’m not at this temperature and in fact the reactions that offers have not sense.
How can fix Temperature?
fix 1 mobile nvt temp 500 500 50 is not correct?
Change your damping factor and if it does not help, then you might have bad dynamics from bad force field and/or bad structure.
Field.reax correctly describes nitrogen?
We don’t know which force field description you are using…
Ray