  We present, here, advanced DFT-NEGF techniques that we have implemented in
our ATOmistic MOdelling Solver, ATOMOS, to explore transport in novel materials
and devices and in particular in van-der-Waals heterojunction transistors. We
describe our methodologies using plane-wave DFT, followed by a Wannierization
step, and linear combination of atomic orbital DFT, that leads to an orthogonal
and non-orthogonal NEGF model, respectively. We then describe in detail our
non-orthogonal NEGF implementation including the Sancho-Rubio and
electron-phonon scattering within a non-orthogonal framework. We also present
our methodology to extract electron-phonon coupling from first principle and
include them in our transport simulations. Finally, we apply our methods
towards the exploration of novel 2D materials and devices. This includes 2D
material selection and the Dynamically-Doped FET for ultimately scaled MOSFETS,
the exploration of vdW TFETs, in particular the HfS2/WSe2 TFET that could
achieve high on-current levels, and the study of Schottky-barrier height and
transport through a metal-semiconducting WTe2/WS2 VDW junction transistor.
