Calculating stored bond energies

Submitted by SHUBHAM AGARWAL on Fri, 07/16/2021 - 23:17

Hello
I am using "LIGGGHTS-flexible fibres"
For my study, I need to calculate energy stored in bonds such as normal, shear and bending. Is there a command to directly calculate that ?
If not, is there a way to find bond forces in normal, shear, moment, so that I can find energies by integration? As I can see the 'compute property/local ' can give bond forces in X, Y, Z not in normal and shear.

Thanks
Shubham

Forums:

mschramm | Mon, 07/19/2021 - 16:40

Hello,
total bond energy is calculated each step and can be accessed as a thermo command (like kinetic energy) via
thermo_style custom step atoms numbonds ke bondEnergy

This is the total potential energy in the bonds added together.
If you need them to be separated, you will need to use a "compute property/local" command.
compute bc all property/local batom1x batom1y batom1z batom2x batom2y batom2z batom1 batom2 btype bforceX bforceY bforceZ btorqueX btorqueY btorqueZ beqdist

Here you can calculate the potential energy in a bond by (bforceX*bforceX/Kn) to calculate the normal bond force energy.

SHUBHAM AGARWAL | Mon, 07/19/2021 - 21:04

Hell0
Thanks a lot
The above compute style gives bond force in X,Y and Z direction. I think I need to resolve those in normal and shear direction to calculated energy stored in normal and shear modes.
Also I also want to calculate the energy in bending, for that I need to store rotation of each atom, is there any command for that?

Shubham