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PhD. Delvany de Castro Gomes

DelvanyPh.D. completed in 2022. Theoretical studies of reaction between atomic Silicon and diatomic species have been reported, Yue and Gan presented an ab initio study of the Si + H2 potential energy surface, while Rivero et al. reported a Time-Dependent Quantum Wave Packet Study of the Si + OH → SiO + H reaction.

As pointed out elsewhere, a full theoretical description of an atom- diatom collision (within the Born-Oppenheimer approximation) considering both reactive channels and inelastic scattering requires the potential energy surface (PES) for the molecular system. Once the PES is accurately represented it can be used for molecular dynamics studies, describing then the reaction probabilities and molecular energy transfer during a collision. Yet, this methodological pathway is not straightforward.

Construct an accurate global potential energy surface for a triatomic system deals with a function depending upon three interatomic distances. This function is usually required to reproduce high level ab initio calculations for the molecular system. Parameters are carefully fine-tuned or fitted to the available data on the studied system. Then, classical or quantum mechanics dynamics calculations using such a PES can be applied for the study of the molecular collision.

To analytically represents a global PES, the many-body expansion (MBE) methodology have been extensively used. In the frame of MBE, each many body energy term can be splitted into two parts. Within this idea, Varandas and collaborators developed the double many-body expansion, similarly Aguado and Paniagua has also proposed its long plus short range epresentation. Both methodologies have been applied to several molecular systems.

For molecular dynamics, since the works by Karplus et al. quasi-classical trajectories have been a fundamental tool for the studying of molecular collisions. Molecular quantum dynamics, using wave packets has also raised as a practical methodology for such studies.

The aim of this project is to theoretically study the addition of silicon to mercapto radical:

Si + HS → products developing global PES for SiSH for the use in molecular dynamics calculations.


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