how to calculate the strain energy for polymers

Thank you for reply.

Running my huge system of epoxy twice is not very efficient but if there is not any other way to extract the strain energy I guess I have to do it.

I was wondering if you have another suggestion for calculating the Young’s modulus of an polymeric system.

Best regards,

Shahin

That was just a suggestion. You can also run, while pulling slowly,
and measure energy, stress, etc. It's up to you. You need to
translate "measure strain energy" into something meaningful
at an atomic level in a molecular simulation.

Steve