# Work Function Problem

2D materials (such as graphene) are mostly exfoliated from their 3D bulk counterpart. I am wondering how we can calculate work function for a 2D material? Normally electrostatic potential in the out-of-plane direction is required to obtain E$$_{\rm{vac}}$$, which is later used in the definition of work function (WF=E$$_{\rm{vac}}$$-E$$_{\rm{Fermi}}$$).

Do we need electrostatic potential for both bulk and 2D system to compute work function or is it only the 2D material for which it should be computed?