Dear Sahil, 

you can draw model using GausView. Or more simply if you want you can use:

Avogadro (it is freeware)

http://avogadro.cc/wiki/Main_Page

and export the model as a  .pdb file

Kind regards,

Avni

Thanks Dr. Avni Berisha

                                    Although I have Gauss view and avagadro....but i am not finding any demo video so that i can draw specifically graphene composite....anyways thanks....let me try..

With Regards

Send me a hand drawn photo of your structure, to see if a can help you.

Kind regards,

Avni