difference in ReaxFf implementation between standalone and LAMMPS

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1

Dear Sumanthy,

This problem has been resolved already. The inconsistency between lammps and reaxff is because you need to manually provide seed to generate initial velocity in lammps, for temperature of 3000K, a line like this is needed:

velocity all create 3000.0 54912115 dist gaussian sum no rot yes units box

Check the lammps manual for velocity to find more.

Best,
Qing

2

Hi Qing,

To answer your second question (if you have not had the answer
already), you can use fix reax/c/species.

Ray

3

Hi Ray,

Thanks a lot for the hint! I had used fix reax/bond for a while,
really glad lammps added fix species last April, it truly makes things
a lot easier.

Best,
Qing

4

Dear Ray

Just want to know how fix/species works for highly dense system like a box of NO at a density of 1.3 g/cc.

Do you have any experience to share.

Thanking you

With regards
Sumathy

5

Hi Sumathy,

Fix reax/c/species determines bonds and molecules based on
user-defined bond order cutoff values, instead of cutoff distances.
Therefore for dense systems if ReaxFF is still producing the correct
connectivity, hence the correct bond order, there should not be a
problem for fix reax/c/species.

On the other hand, BO values may increase for dense systems due to
shorter bond lengths. It may help to define slightly larger BO cutoff
values in fix reax/c/species for denser systems.

Thanks,
Ray