  The accuracy of a single s-orbital representation of Cu towards enabling
multi-thousand atom ab initio calculations of electronic structure is evaluated
in this work. If an electrostatic compensation charge of approximately 0.3
electrons per atom is used in this basis representation of copper, the
electronic transmission in bulk and nanocrystalline Cu compares accurately to
that obtained with a Double Zeta Polarized basis set. The use of this
representation is analogous to the use of single band effective mass
representation for semiconductor electronic structure. With a basis of just one
s-orbital per Cu atom, the representation is extremely computationally
efficient and can be used to provide much needed ab initio insight into
electronic transport in nanocrystalline Cu interconnects at realistic
dimensions.
