  We present current-voltage (I-V) curves computed using all-electron basis
sets on the conducting molecule. The all-electron results are very similar to
previous results obtained using effective core potentials (ECP). A hybrid
integration scheme is used that keeps the all-electron calculations cost
competitive with respect to the ECP calculations. By neglecting the coupling of
states to the contacts below a fixed energy cutoff, the density matrix for the
core electrons can be evaluated analytically. The full density matrix is formed
by adding this core contribution to the valence part that is evaluated
numerically. Expanding the definition of the core in the all-electron
calculations significantly reduces the computational effort and, up to biases
of about 2 V, the results are very similar to those obtained using more
rigorous approaches. The convergence of the I-V curves and transmission
coefficients with respect to basis set is discussed. The addition of diffuse
functions is critical in approaching basis set completeness.
