  We present a computational method to quantitatively describe the
linear-response conductance of nanoscale devices in the Kondo regime. This
method relies on a projection scheme to extract an Anderson impurity model from
the results of density functional theory and non-equilibrium Green's functions
calculations. The Anderson impurity model is then solved by continuous time
quantum Monte Carlo. The developed formalism allows us to separate the
different contributions to the transport, including coherent or non-coherent
transport channels, and also the quantum interference between impurity and
background transmission. We apply the method to a scanning tunneling microscope
setup for the 1,3,5-triphenyl-6-oxoverdazyl (TOV) stable radical molecule
adsorbed on gold. The TOV molecule has one unpaired electron, which when
brought in contact with metal electrodes behaves like a prototypical single
Anderson impurity. We evaluate the Kondo temperature, the finite temperature
spectral function and transport properties, finding good agreement with
published experimental results.
