  We present a generalized approach for computing electron conductance and I-V
characteristics in multiterminal junctions from first-principles. Within the
framework of Keldysh theory, electron transmission is evaluated employing an
O(N) method for electronic-structure calculations. The nonequilibrium Green
function for the nonequilibrium electron density of the multiterminal junction
is computed self-consistently by solving Poisson equation after applying a
realistic bias. We illustrate the suitability of the method on two examples of
four-terminal systems, a radialene molecule connected to carbon chains and two
crossed carbon chains brought together closer and closer. We describe charge
density, potential profile, and transmission of electrons between any two
terminals. Finally, we discuss the applicability of this technique to study
complex electronic devices.
