some questions in reax/c?

Dear all
I am using reax/c during the NEMD simulation with wall/reflection.The system is RDX crystal.I have some questions about the reax/c:

  1. how to calculate the bond energy, such as C-C, C-H, C-N et al. bong energy?
    I saw the manual and found the compute bond/local command may calculate the bond energy.

compute 2 all bond/local dist engpot
dump 1 all local 1000 tmp.dump index c_2[*]

ERROR: Compute bond/local used when bonds are not allowed.

How to modify it?

  1. how to subtract the center-of-mass velocity?

compute myTemp all temp/com
compute RDXX hot chunk/atom bin/2d x 0 5 y 0 5 units box

fix 6 hot ave/chunk 100 1 1000 RDXX vx vy vz temp density/mass bias myTemp norm sample file tmp_RDX.out

The temp in fix command is the real temperature, is it right?

  1. how to calculate the real press?

In lammps, the press is computed by the formula


compute peratom hot stress/atom NULL
variable meanpress1 atom -(c_peratom[1]+c_peratom[2]+c_peratom[3])/3

fix 7 hot ave/chunk 100 1 1000 RDXX v_meanpress1 norm sample file tmp_RDX_press.out

Is the v_meanpress1 in fix command the real press?

Hello, I also use ReaxFF potential file.

Question 1. You need to make particular program to analyze bond energy in ReaxFF. As far as I know, LAMMPS can not obtain such data by its integrated commands.

Question 2. Please check “fix momentum” command.

Question 3. Please check “compute stress/atom” command in manual. There is an example to calculate the pressure you want.


Compute bond/local works for models with fixed explicit bond topology,

e.g. see the bond_style command. ReaxFF (and other bond-order

potentials) have implicit bonds.