# Calculating bond energy of specific bond (reaxff)

Hello,

I am trying to calculate the bond dissociation energy (using ReaxFF) of a specific bond in a system. I am aware that the following command gives the different energy components, including the bond energy.

compute varname all pair reax/c

However, I am not able to use this command with any other group except “all”. So if I want to calculate the bond dissociation energy (or the bond energy) for a specific group of atoms, is there another command (or a more indirect approach) to do this?

Thank you!

2015-01-27 8:14 GMT+01:00 Nithya Subramanian <[email protected]...>:

Hello,

I am trying to calculate the bond dissociation energy (using ReaxFF) of a
specific bond in a system. I am aware that the following command gives the
different energy components, including the bond energy.

compute varname all pair reax/c

However, I am not able to use this command with any other group except
"all". So if I want to calculate the bond dissociation energy (or the bond
energy) for a specific group of atoms, is there another command (or a more
indirect approach) to do this?

First, be aware of the fact that Ebond term in ReaxFF is not the bond
dissociation energy, in the sense that it's just one of the many terms that
contribute to the energy difference between a bound and an unbound state
(torsion interactions, the repulsive vdw term, angle term etc. also change
during dissociation).

Typically, obtaining the correct (according to the potential) bde will only
be possible from two calculations: one of the bound, and one of the unbound
system. You probably can get an approximation by using compute pe/atom to
get an idea of how every atom contributes.

Kristof

Yes, I am trying to compare the bond energy of a specific group of atoms in a bound state and an unbound state. the difference is used to calculate the BDE. To generate the unbound state, I am applying atom forces to break specific bonds in the group. However, even with the compute pe/atom command, the bond interactions cannot be extracted because I am using a reactive force field (which does not contain any explicit bond information).

Is there another way to compute BDE?