Electronic structure and transport in molecular and nanoscale electronics

Two approaches based on first-principles method are developed to qualitatively and quantitatively study electronic structure and phase-coherent transport in molecular and nanoscale electronics, where both quantum mechanical nature of electrons and dimensionality of systems play the critical roles in their electronic, magnetic and optical properties. Our first approach is based on Green's function method with ab initio quasiatomic orbitals within Landauer formalism. To efficiently and accurately apply Green's function method, we develop a minimal basis-set of quasiatomic orbitals from plane-wave density functional theory (DFT) results. This minimal basis-set resembles quasi-angular momentum characteristics in solid state systems and it further validates Slater's original idea of linear combinations of atomic orbitals. Based on their ab initio tight-binding matrices, the accuracy, efficiency and stability of our scheme are demonstrated by various examples, including band structure, Fermi surface, Mülliken charge, bond order, and quasiatomic-orbitals-projected band structure and quasiatomic-orbitals-projected Fermi surface. Remarkably these quasiatomic orbitals reveal the symmetry and chemical bonding nature of different molecular, surface and solid systems. With this minimal basis-set, quantum conductance and density of states of coherent electron transport are calculated by Green's function method in the Landauer formalism. Several molecular and nanoscale systems are investigated including atomic wires, benzene dithiolate, phenalenyl dithiolate and carbon nanotube with and without different types of defects.

Department dc:contributor.department

Massachusetts Institute of Technology. Dept. of Nuclear Science and Engineering.

Grantor dc:publisher

Massachusetts Institute of Technology

Year dc:date.issued

2008

Author dc:creator

• Qian, Xiaofeng

Advisor dc:contributor.advisor

• Sidney Yip.

• Nuclear Science and Engineering.

Statement dc:rights

• M.I.T. theses are protected by copyright. They may be viewed from this source for any purpose, but reproduction or distribution in any format is prohibited without written permission. See provided URL for inquiries about permission.

Licence dc:rights.uri

• http://dspace.mit.edu/handle/1721.1/7582

Language dc:language.iso

eng

Handle dc:identifier.uri

http://hdl.handle.net/1721.1/44783

OAI identifier oai:identifier

oai:dspace.mit.edu:1721.1/44783