I am trying to reproduce a paper titled-"Adsorption of the water molecule on monolayer graphene surface" and for that purpose I am using castep tool from material studio software.I have created a layer of graphine manually but castep takes periodic cell as input.So it didn't work.Now I am looking for the procedure to generate 4x4x1 monolayer graphene from graphite crystal.I have read the tutorial of MS software named 'Adsorption of CO onto a Pd(110) surface'.But I have some confusion like weather I have to cleave the graphite cell or not.