Time-Dependent Density Functional Theory with Ultrasoft Pseudopotential: Real-Time Electron Propagation across Molecular Junction

摘要

A practical computational scheme based on time-dependent density functionaltheory (TDDFT) and ultrasoft pseudopotential (USPP) is developed to studyelectron dynamics in real time. A modified Crank-Nicolson time-steppingalgorithm is adopted, under planewave basis. The scheme is validated bycalculating the optical absorption spectra for sodium dimer and benzenemolecule. As an application of this USPP-TDDFT formalism, we compute the timeevolution of a test electron packet at the Fermi energy of the left metalliclead crossing a benzene-(1,4)-dithiolate junction. A transmission probabilityof 5-7%, corresponding to a conductance of 4.0-5.6muS, is obtained. Theseresults are consistent with complex band structure estimates, and Green'sfunction calculation results at small bias voltages.