Real time TDDFT study of electron induced chemical reactions in polymers

To study attosecond electron dynamics, the method of real-time Time Dependent Density Functional Theory (rt-TDDFT) was proposed and developed since 1980’s. However, the rt-TDDFT predictions for electron scattering induced electronic excitation and further chemical reactions are still scarce. Electron driven chemistry is important for a wide variety of applications including plasma etching, photoresist cure and lithography. We present a quantitative study on the inelastic electron scattering processes with an electron wave packet incident on a model organic strand including modified benzene rings and phenyl groups, based on the rt-TDDFT and Ehrenfest dynamics simulations. We will show the relationship between electronic excitations and bond dissociation probabilities by the excited electron population evolution and following non-adiabatic Ehrenfest molecular dynamics. The partitioning of the incident electron energy into electronic excited states and phonon modes is important for large polymer strands. The most reactive portions of our model polymer strand are phenyl groups for which we present a detailed cross-section as a function of electron energy. In summary, our study provides an insight into the essential mechanisms of excited electron dynamics in polymers. TDDFT shows promise as a means of characterizing otherwise unmeasurable inelastic electron scattering process relevant to semiconductor device fabrication.