Dear Muhammad Ali Musarat , I imagine what you call "fractional coordinates" is the fraction of Graphene Nano-Platelets (GNP) in a matrix of PDMS. These "fractional coordinates" can be found quite easily in the literature and this fraction should be adapated to your application, since some applications will require a low fraction of GNP´s and some other a larger one, even a saturated one could be interesting in some cases.

I think you can find the following papers of interest, please have a look to them:

Article A comparative study of two graphene based elastomeric compos...

Article Graphene-nanoplatelet-based photomechanical actuators

Article Characterizing PDMS/MWCNTs and PDMS/GNP composites for biopo...

Article Flexibility and sensitivity of graphene nanoplatelets-polydi...

I hope it helps.

Manuel Gómez Thank you for your detailed answer. I will check these articles.