Dear LAMMPS Users,

I am trying to calculate the 21 elastic constants of a nanowire. The example case in the LAMMPS package, ELASTIC, computes the 21 elastic constants. The system in this example does not have any interfaces. In other words, it’s modeling bulk material. Can I use the same method to calculate the elastic constants for a nanowire including the nanowire-air interfaces?

Thanks for your help!

Sincerely,

Han Hu

The biggest complication in using an interface is not specific to LAMMPS or even MD, it is just that the volume enclosing the material is not the volume of the unit cell.

If you have a reasonably precise way to define the nanowire’s geometrical shape and volume, you can correct the stress computed assuming a bulk volume to account for just the part that is filled by atoms. Most engineering mechanics textbooks should be able to help you find the correct mathematical expressions for e.g. a cylindrical rod.

Giacomo