wrong density of water with reaxffo

Hello

I simulated 900 waters with Reaxff by lammps (version Feb 1 2014) . The simluation was performed in a NPT ensemble.

here is the input script

units real
atom_style full
dimension 3
neighbor 2.0 bin
boundary p p p

read_data watermar62.data

#pair potentials
pair_style reax/c lmp_control safezone 1.6 mincap 100
pair_coeff * * ffield.reax.cho O H

fix 0 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c
fix 1 all npt temp 300.0 300.0 100.0 iso 1.0 1.0 1000.0

minimize 1.0e-4 1.0e-6 100 1000

but when it is stable , the density is about 1.8g/ml . I am very confused why it happen,and is reaxff suitable to simulate the pure water?

I’d appreciate if you can tell me the reason why errors happen and how to fix them !

sincerely

watermar62.data (125 KB)

reax.in (857 Bytes)

ffield.reax (7.78 KB)

lmp_control (1005 Bytes)

log.lammps (72.6 KB)

2016-03-07 5:04 GMT+01:00 ChangEgbert <[email protected]>:

Hello

I simulated 900 waters with Reaxff by lammps (version Feb 1 2014) . The
simluation was performed in a NPT ensemble.

here is the input script

units real
atom_style full
dimension 3
neighbor 2.0 bin
boundary p p p

read_data watermar62.data

#pair potentials
pair_style reax/c lmp_control safezone 1.6 mincap 100
pair_coeff * * ffield.reax.cho O H

fix 0 all qeq/reax 1 0.0 10.0 1.0e-6 reax/c
fix 1 all npt temp 300.0 300.0 100.0 iso 1.0 1.0 1000.0

minimize 1.0e-4 1.0e-6 100 1000

but when it is stable , the density is about 1.8g/ml . I am very confused
why it happen,and is reaxff suitable to simulate the pure water?

You should check whether the *specific parameters* you use are suitable for
liquid water. The C/H/O force field is intended for hydrocarbon combustion,
so liquid water was not part of the training set. However, there are other
ReaxFF parameterizations that are designed for systems containing liquid
water. There are quite a few, and I don't know how they relate to each
other, so this is a thing you have to check for yourself. As a logical
starting place, have look here:
http://authors.library.caltech.edu/62239/1/9781849734905-00223.pdf

Kristof