Nonadiabatic Direct Dynamics Simulation of Photoinduced Isomerization of Cubic Hydrogen Silsesquioxane

We have developed Si parameters for the orthogonalization and dispersion corrected semiempirical method, ODM3. The new parameter set is called ODM3.25. As an illustration of the new capability allowed by these new parameters, we simulated the nonadiabatic dynamics of the cubic hydrogen silsesquioxane (Si₈O₁₂H₈, HSQ) electron beam photoresist by using curvature-driven trajectory surface hopping with energy-based decoherence (κTSH-EDC) interfaced with ODM3.25. Our simulations involve four coupled singlet states and four coupled potential energy surfaces. The isomerization of the HSQ molecule involves an interconversion of kinetic energy and potential energy during the first 100 fs, and this is followed by Si-H bond breaking and O-H bond formation. We find that about a quarter of the product remains in an electronically excited state. We anticipate that the combination of the cost-effective ODM3.25 with curvature-driven algorithms for electronically nonadiabatic dynamics will allow simulations of nonadiabatic dynamics in a broad range of problems involving Si-containing nanoparticles.