Classical canonical transformation theory as a tool to describe multidimensional tunnelling in reactive scattering. Hopping method revisited and collinear H+H2 exchange reaction near the classical threshold

Classical canonical perturbation theory is applied in the vicinity of the saddle point for a chemical reaction. This is done by applying successive canonical transformations in the scope of the Gustavson–Birkhoff approach. It is shown that the calculated approximate classical integrals of motion can be used to describe classically forbidden tunnelling processes. They are also organically embedded into a hopping method to incorporate tunnelling effects into classical trajectory simulations of chemical reactions. The applicability of the proposed scheme is demonstrated for the collinear H+H2 exchange reaction using the double many-body expansion potential energy surface.Fundação para a Ciência e Tecnologia, programas PRAXIS XXI e FEDER

Impact of Attractive Ion in Undoped Channel on Characteristics of Nanoscale Multigate Field Effect Transistors: A Three-Dimensional Nonequilibrium Green's Function Study

A rigorous simulation study of the impact of a single attractive ion in undoped channel multigate field-effect transistors is presented using a new three-dimensional nonequilibrium Green's function technique. A single donor induces threshold voltage shift, and its impact is most significant when the donor is located at the top of the potential barrier. On the other hand, on-current is not affected so much because of the electrostatic screening by the electron bound around the positively charged ion. To reduce the intrinsic device parameter fluctuation, a gate-all-around structure has better robustness than the double gate structure. </jats:p