mse8210 advanced topics in theoretical surface and ...yonseimtg.weebly.com › uploads › 3 › 5...

MSE8210Advanced Topics in Theoretical Surface and Interface Science

Aloysius Soon알로이시우스 손

[email protected]

Course outline

• An introduction to fundamental concepts in theoretical surface science

• Processes that occur at surfaces and interfaces: critical role in manufacture and performance of advanced materials (e.g. electronic, magnetic and optical devices, sensors, catalysts andhard coatings).

• Focus of this course: high-level, ab initio approaches to understanding surface and interface science phenomena.

• First-principles electronic structure calculations and how they can be used to probe chemo-physical properties of surfaces and interfaces (Principles and concepts are IMPORTANT)

Lesson plan

• Part One: Fundamentals of electronic structure and condensed matter theory [3 lessons]

• Part Two: Metal surfaces and simple adsorption [4 lessons]

• Part Three: Metal alloys and their surfaces [2 lessons]

• Part Four: Moving towards reality – ab initio atomistic thermodynamics [2 lessons]

• Part Five: Special lectures – Open questions in theoretical surface science [2 lectures]

• Revision before examination

Assessment

• Attendance = 20 % [Active class participation is crucial !!]

• Assignments/Student-presentation = 20 %

• Two assignments (Report + Oral)

• Mid-term project (Report + Oral) = 30 %

• Final examination = 30 %

Note: All lectures, assignments, presentation, discussions etc. will be given in English.

GOAL: Effectively communicate science in basic English

Lecture materials

Assumption: Basic knowledge of solid-state and surface physics/chemistry, elementary band theory and basic quantum mechanics/density-functional theory

• Lecture notes/outline provided

• Reference materials

• Electronic Structure: Basic Theory and Practical Methods by Richard Martin – For background reading

• Theoretical Surface Science: A Microscopic Perspective by Axel Gross

• Extra reading materials will be made known along the way

New learning approaches

Problem-based learning (PBL) is a student-centeredinstructional strategy in which students collaboratively solve problems and reflect on their experiences

• Learning is driven by challenging, open-ended problems

• Students work in small collaborative groups

• Teachers take on the role as "facilitators" of learning

Project-based learning is the use of classroom projects, intended to bring about deep learning, where students use technology (e.g. the Internet, library, scholarly articles etc.) and inquiry to engage with issues and questions of interest

New learning approaches

About Aloysius 알로이시우스

• I’m from Singapore and my native language is English.

• I do not (yet) speak/understand Korean (fluently)

• I value and practice “open-concept” teaching i.e. I do not think that scientific pursuit is only for the SMART guys, but is just as easily available for the curious and passionate – that’s YOU !!

• I am here to learn as much from YOU, as you from me. YOU have much to offer.

• Most importantly, I’m a NEWBIE, so please be nice !!

About Aloysius 알로이시우스

• B.Sc. (Hons) ChemistryNational University of Singapore, Singapore

• M.Sc. ChemistryUniversity of Auckland, New Zealand

• Ph.D. PhysicsUniversity of Sydney, Australia

• MPG/AvH Fellow Physics/ChemistryFritz-Haber-Institut der Max-Planck-Gesellschaft, Germany

Now, it’s your turn. Tell me something about yourself

Now, it’s your turn. Tell me something about yourself

• Computational modelling of materials properties and phenomena: from the synthesis, characterisation and processing of materials, structures and devices to the numerical methodology of materials simulations (quantum and classical)

• Other common and closely-related fields: Condensed matter theory, Solid-state theory (both physics and chemistry), nanoscience and nanotechnology, etc.

• NOT an isolated field, VERY active field: Best to go hand-in-hand with experiments and theory

Computational Materials Science

Experiments TheoryModelling

• From Physics Today, June, 2005

• 11 papers published since 1893 with > 1000 citations in APS journals

Computational Materials Science

• Study of physical and chemical phenomena that occur at the interface of two phases, including solid-liquid interfaces, solid-gas interfaces, solid-vacuum interfaces, and liquid-gasinterfaces – surface physics and surface chemistry

• The field of surface chemistry started with heterogeneous catalysis pioneered by Paul Sabatier on hydrogenation and Fritz Haber on the Haber process

• Most recent developments in surface sciences include the 2007 Nobel Prize of Chemistry winner Gerhard Ertl'sadvancements in surface chemistry, specifically his investigation of the interaction between carbon monoxide molecules and platinum surfaces

Surface Science

• Tremendous progress in the microscopic theoretical treatment of surfaces and processes on surfaces

• A wide range of surface properties can now be described from first principles, i.e. without using any empirical parameters

• Level of sophistication and accuracy that reliable predictions for CERTAIN surface science problems is now possible

• Detailed theoretical understanding will have wide applications in a range of physical, chemical, biological, medical engineering and material science problems

Theoretical Surface Science

Experiments TheoryModelling

• Describes the behaviour of electrons in atoms, molecules and solids, namely (in hope of) solving the many-body Schrödinger equation

• Probes the quantum nature of electrons – Quantum mechanics!

• Usually “mathematically” involved, but can be (attempted to) explained at a simple level for non-experts – Goal of this course!

• So let’s try.

Electronic structure theory

H Ψ = E Ψ

Lesson 1.1From atoms to solids – An overview

FundamentalsFrom alpha to omega

• Classical picture – “planets orbiting around the sun”

• Quantum picture – Statistics came into play: Where is the most probable location of the electron? No longer orbits but orbitals (and wavefunctions)!

proton neutron

electron


• Electron configuration = arrangement of electrons in an atom, molecule, or other physical structure (e.g., a crystal).

• Knowing this for different atoms is useful in understanding the structure of the periodic table of elements –describing the chemical bonds that hold atoms together.

Ener

gy

1s

2s

3s

4s

2p

3p

4p 3d


What if we mix-and-match the orbitals of different atoms in a molecule, e.g. H2 ?


Ener

gy

1sH

1sH

σ*

σ

• Atomic orbitals (AO) combine = molecular orbitals (MO)

• MO diagram represents the interaction between the AO

AO1

σ*

σ

AO2AO1

σ*

σAO2

Non-polar bond Polar bondSemi-polar bond

What if, now, we mix-and-match the orbitals of many (almost infinite) number of atoms, e.g. in a crystal ?


• Many MOs combine to form continuous bands or states

• Band diagrams are useful – understand and characterize materials of different electronic/optical properties

Band diagram

Ener

gy InfiniteMOs

HOMO | VBM

LUMO | CBM

Metal Semiconductor Insulator

Fermi level

Overlaping states


Adapted from “Atomic and Electronic Structure of Solids” – Efthimios Kaxiras






• Opening of the hybridization bandgap

• From C to Sn, atomic size increases bandgap decreases



• Interband transitions in a semiconductor, between valence and conduction states

• Intraband transitions in a metal across the Fermi level

indirectdirect


• The density-of-states (dos) describes the energy levels per unit energy increment.

• Non-uniform across the band: Levels are packed more closely together at some energies than others as a result of overlap of the molecular orbitals.

Density-of-states

Ener

gy

What is the area under the graph ?


• Density-of-states

• Sum over all (eigen)states/orbitals with eigenvalues, εi of the electronic hamiltonian

• Projected (or local) density-of-states


• The Fermi-Dirac distribution is characterized by the temperature of the electrons, and the Fermi level

Absolute 0 KSmall electronic entropy

Large electronic entropy

Fermi level

Conduction band

Valence band


• Relative filling of the d and sp density-of-states – moving across the transition metal series


Cohesive energy or

Atomization energy


(Murnaghan) Equation of State: Binding-energy relation Cohesion

Relative volume

Ener

gy


• Types of bonding classified by cohesion strength

• Something measurable by both experiments and computation

• Special attention is to be made when choosing (1) the type of model and (2) level of theory to use


• Very basic concepts: electronic configuration, orbitals, types of bonding, simple crystallography, band theory (bandstructureand density-of-states), etc.

• To be built upon for lessons to come (Not necessarily tested in the examinations, but good to know)

• PROMISE: Not too much tedious, difficult mathematics – only equations that exemplify a concept

• PROMISE: A lot of readings to do! I do not expect you to immediately understand everything, but I will highlight the key points to learnhttp://www.fhi-berlin.mpg.de/th/publications/Handbook-of-Surface-Science-286-2000.pdf

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