Periodic Boundary condition in a multiphysics.

Hello everyone,

I am new to COMSOL, and I was in a confusion about the boundary conditions applied to the multiphysics. I am working on a piezoelectric model and want to apply periodic BC to the model. Do I need to apply it from both physics (solid mechanics and electrostatics) or it is fine if I apply it from just solid mechanics. I also want to know about how to apply initial or external strains on points rather than domain.

Thanks