Elastic constants for monoclinic NiTi B19'

Dear All,

I am trying to calculate the elastic constants of NiTi crystal for benchmarking with the published values using the script provided in the lammps example directory (/lammps-12Dec18/examples/ELASTIC). For cubic B2 (Austenite), I am getting the exact values but for monoclinic B19’ NiTi (martensite), the offset in the elastic constants produced in way higher than the published values.

Could you please tell me if the script is equally good for calculating elastic constants for non-orthogonal (monoclinic) systems or do I need to change something to make it accurately working for these systems.

Thank you

Meghnath

Dear All,

I am trying to calculate the elastic constants of NiTi crystal for
benchmarking with the published values using the�script provided in
the lammps exampledirectory (/lammps-12Dec18/examples/ELASTIC). For
cubic B2�(Austenite),�I�am getting the exact values but for monoclinic
B19' NiTi (martensite), the offset in the elastic constants
produced�in way higher than the published values.

Could you please tell me if the script is equally good for calculating
elastic constants for non-orthogonal (monoclinic) systems or do I need
to change something to�make it accurately working for these systems.

What I have seen, is that this script is very "unstable" when the system
is not simple (complex crystallography, multi-element,...). I suppose it
come from the force-field energies/forces that become more difficult to
properly minimize while applying a tiny homogeneous deformation. But I
might be completely wrong...

What I do usually, is to increase the number of particles in my system,
and vary the jiggle (move way from an already-almost-relaxed state) and
strain-factor (as already mentioned in the comments of the script)
parameters until I'm getting "stable" elastic constant.

Julien