I am using QATK ver 2016.4 perpetual licence.

We have used Brenner (ASAP) potential parameter set for calculating the classical potential of a phonon (for SiNR and GeNR). Tersoff SiGe potential set is used with frozen phonon method. To calculate the phonon properties, i.e. forces and dynamical matrix 180 small displacements measuring 0.01 Ǻ are applied. The heat current is calculated considering the contribution of both electron and phonon. The transport calculations are carried out with the Landauer theory and the non-equilibrium Green’s function (NEGF) framework in Atomistix Tool Kit (ATK).

Is WKB approximation valid under such a scenario?