Theory of quantum transport at the molecular scale

Alshammari, Mohammed and Lambert, Colin (2025) Theory of quantum transport at the molecular scale. PhD thesis, Lancaster University.

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Abstract

Abstract Molecular electronics is a valuable tool for studying nanoscale thermoelectricity and discover ing new organic thermoelectric materials that are both low-cost and environmentally friendly. This thesis describes the theoretical methods used to support this procedure, beginning with chapters 2 and 3, respectively. I have described the essential equations and methodologies that drive my work, such as the Schrodinger equation, density functional theory (DFT), and the SIESTA programs, which is in charge of implementing DFT and solving the underlying equations. In addition, I explain the single particle transport theory, which is based on the Hamiltonian and Green's functions, and provide some examples of how it might be applied. Chapter 4. Therefore, I investigated the transport characteristics of a HATNA series of single-molecule junctions, which includes molecules that, upon reduction by hydrogen, change between high and low conductance states, at least in the SAMs.This dynamic molecular switch can supply all basic logic gates due to its time-domain and voltage- dependent plasticity, which mimics synaptic behaviour and Pavlovian learning. Chapter 5. This chapter covers the transport features of stable organic radicals for electrical devices, which are caused by their half-filled orbitals approaching Fermi energy. Also, observe the systematic changes that occur when the hydrogen is removed from the OH groups to generate radicals, and how this affects electrical conductivity.