Title

Estimation of the Nuclear Quantum Effects in Molecualr Systems

Date of Award

Spring 2019

Document Type

Open Access Thesis

Department

Chemistry and Biochemistry

First Advisor

Sophya Garashchuk

Abstract

Quantum dynamics simulations are powerful tools for understanding the mechanisms and the rates of the chemical reactions with the time evolution of chemical systems. It gives the comprehensive view of the chemical processes. In most cases, classical de- scription of the nuclei is appropriate for having clear insights and making comparison with experimental quantities. However, there are situations where nuclear quantum effects are important to explain some experimental observations. Nuclear quantum effects such as tunneling effect, zero-point energy (ZPE) effect and nonadiabatic tran- sitions are important for the accurate description and understanding of reactions in complex chemical environments such as solutions, solids and nanomaterials.

In the thesis, the exact quantum mechanical scattering approach is performed to evaluate the nuclear quantum effects on proton conductance through atomically thin films of hexagonal boron nitride and graphene. The recent experimental evidences suggests that atomically thin hexagonal boron nitride and graphene are permeable to protons and deuterons and also there are some disagreements between the theoretical estimates for the isolated proton-membrane transfer model. First, The process is examined within a molecular model of H2O - H(D)+ - material - H2O. The analysis of the potential energy surfaces is obtained by correlated electronic structure calculations. Through the application of quantum scattering calculations, the nuclear quantum effects such as tunneling factors and kinetic isotope effect are evaluated.

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