The construction of electrode has been clearly mentioned by that paper, see below
"The leads are modeled by six layers of Al in the (111) orientation with a graphene monolayer placed at a distance of 0.34 nm away, in the minimal-energy configuration"
The steps to construct it:
i) cleave a (111) surface of Al using VNL. In this step, you can obtain the primitive cell of slab model of Al(111). Other point is that the normal direction of atomic layer in slab had better be chosen along the z direction.
ii) put a monolayer graphene on the top of Al(111). The relative positions of C atoms in graphene with respect to the topmost layer of Al(111) can be found in the Figure 1 of PRL 101, 026803 (2008).
iii) Once the primitive cell of slab for the interface of Al(111) and graphene is obtained in the 2nd step, one should extend it in the x and y upto a certain width that is larger than the width of graphene ribbons mentioned in that paper.
Other steps for the constructions of a two-probe system with above electrode can be performed in the usual way.
