The Application of Density Functional Theory in Materials Science Slide 1
Outline Atomistic Modelling Group at MUL Density Functional Theory Numerical Details HPC Cluster at the MU Leoben Applications Slide 2
Atomistic Modelling @ MUL Since November 2005 Head: Prof. Claudia Ambrosch-Draxl Researchers Slide 3
Atomistic Modelling Since November 2005 Head: Prof. Claudia Ambrosch-Draxl Researchers 1 Full Professor, 1 University Assistant 10 PostDocs 5 PhD's 1 Sysadmin... from 9 different countries... Slide 4
Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Development http://exciting code.org/ Slide 5
http://exciting code.org/ Slide 6
Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors electron phonon coupling YBa2Cu3O6+x Slide 7
Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors Organic Semiconductors Flexible Solar Cell (LIOS) Slide 8
Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors Organic Semiconductors Carbon Nanotubes Slide 9
Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors Organic Semiconductors Carbon Nanotubes Metallic Alloys Slide 10
Electronic Structure Problem Coulomb Force = type of bonding Quantum Mechanics + crystal structure elastic constants lattice vibrations band structure Slide 11
Many Electron Problem Total Electronic Hamiltonian e Zp+ Many electron Schrödinger equation Slide 12
Electron Density as a Loophole Electron Density in a (10,0) single walled Carbon Nano Tube Electron density n(r) is the basic variable Density Functional Theory (DFT) provides rigorous framework All microscopic and macroscopic properties depend on n(r) Slide 13
Hohenberg-Kohn Theorem universal functional of the electron density external potential due to atomic nuclei The total energy of a system of interacting electrons is a functional of the density. The energy takes its minimum at the ground state density. Suggestion of Kohn and Sham: exchange correlation energy Slide 14
Kohn-Sham Equations the only approximation! Replace the system of interacting electrons by a fictitious system of non interacting electrons with the same density Slide 15
Kohn-Sham Equations Self the only approximation! consistency Replace the system of interacting electrons by a fictitious system of non interacting electrons with the same density Slide 16
Density Functional Theory (DFT) Walter Kohn Rev. Mod. Phys. 71, 1253 (1999) atomic nuclei electrons DFT Nobelprize 1998 Walter Kohn Slide 17
What Can Be Calculated? Structural Properties Lattice Parameters Elastic Constants Atomic Forces, Equilibrium Geometry Surface Relaxations Defect Structures Lattice Dynamics Vibrational Frequencies Phonon DOS, Vibrational Entropy Electron Density Charge Rearrangements Electric Field Gradients Electronic Structure Band Structure Density of States Spectroscopy Photoemission Electron Energy Loss Optical Absorption Dielectric Function Core Level Spectroscopies Raman Scattering Compton Scattering Positron Annihilation Slide 18
Numerical Approach Kohn Sham equation (differential eigenvalue equation) Linear expansion in known basis functions Kohn Sham equation Matrix Eigenvalue Equation Hamilton matrix Overlap matrix Slide 19
Numerical Approach Slide 20
HPC @ MU Leoben IBM Power 5+ System 74 Computing Nodes 300 Computer Cores about 1000 GByte RAM 9 TByte Storage > 1 TeraFLOP 600 000 Euro Slide 21
HPC @ MU Leoben Slide 22
HPC @ MU Leoben DS4700 Storage and Fileserver (9 TByte) Slide 23
HPC @ MU Leoben 50 Compute Nodes: p505 Power 5+ Quadcore, 8 16 Gbyte RAM/Node Slide 24
HPC @ MU Leoben 10 Compute Nodes: p55a 2 x Power 5+ Quadcore, 32 Gbyte RAM/Node Slide 25
HPC @ MU Leoben 12 Compute Nodes: JS22 Blades, Power 6 Quadcore, 16 GB RAM/Node Slide 26
Job Management Slide 27
Job Management IBM LoadLeveller About 20 users Typically 4 16 cores / job Typical run times: 1 day 1 month Slide 28
Organic Semiconductors Sample of a 10x10 cm2 white OLED (from HC Starck CleviosTM PH510 PEDOT layer) Samsung ultra thin 0.05mm 4 inch OLED display (480 272 resolution, 100,000:1 contrast, 200cd/m2) Organic Solar Cell (Linz Institute for Solar Cells) The work is part of the National Research Network Interface controlled and functionalized organic films Slide 29
Organic -Conjugated Molecules Pentacene (C22H14) OFET Organic Field Effect Transistor Para Sexiphenyl (C36H26) 2.6 nm OLED Organic Light Emitting Diode Slide 30
Angle-Resolved Photoemission h (21eV) e 6P(20 3) Slide 31
Angle-Resolved Photoemission Koller et al., Science 317, 351 (2007). Slide 32
Reconstruction of Molecular Orbitals e h (35eV) kx Slide 33
exp e h (35eV) DFT HOMO Reconstruction of Molecular Orbitals exp DFT LUMO kx Puschnig et al., Science 326, 702 (2009). Slide 34
Stacking Faults in Steel A C B A B A C B A Industry Project within the MPPE centre Motivation for steel industry partners: Development of TWIP steels which combine high strength with high formability Slide 35
Stacking Faults in Steel Reyes Huamantinco, Ruban, Puschnig, Ambrosch Draxl, to be published Slide 36
Thank you for your attention! Slide 37