The Application of Density Functional Theory in Materials Science

Transcription

1 The Application of Density Functional Theory in Materials Science Slide 1

2 Outline Atomistic Modelling Group at MUL Density Functional Theory Numerical Details HPC Cluster at the MU Leoben Applications Slide 2

3 Atomistic MUL Since November 2005 Head: Prof. Claudia Ambrosch-Draxl Researchers Slide 3

4 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

5 Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Development code.org/ Slide 5

6 code.org/ Slide 6

7 Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors electron phonon coupling YBa2Cu3O6+x Slide 7

8 Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors Organic Semiconductors Flexible Solar Cell (LIOS) Slide 8

9 Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors Organic Semiconductors Carbon Nanotubes Slide 9

10 Competences Theoretical Solid State Physics Density Functional Theory Molecular Dynamics Computer Code Develeopment Materials Physics Superconductors Organic Semiconductors Carbon Nanotubes Metallic Alloys Slide 10

11 Electronic Structure Problem Coulomb Force = type of bonding Quantum Mechanics + crystal structure elastic constants lattice vibrations band structure Slide 11

12 Many Electron Problem Total Electronic Hamiltonian e Zp+ Many electron Schrödinger equation Slide 12

13 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

14 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

15 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

16 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

17 Density Functional Theory (DFT) Walter Kohn Rev. Mod. Phys. 71, 1253 (1999) atomic nuclei electrons DFT Nobelprize 1998 Walter Kohn Slide 17

18 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

19 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

20 Numerical Approach Slide 20

21 MU Leoben IBM Power 5+ System 74 Computing Nodes 300 Computer Cores about 1000 GByte RAM 9 TByte Storage > 1 TeraFLOP Euro Slide 21

22 MU Leoben Slide 22

23 MU Leoben DS4700 Storage and Fileserver (9 TByte) Slide 23

24 MU Leoben 50 Compute Nodes: p505 Power 5+ Quadcore, 8 16 Gbyte RAM/Node Slide 24

25 MU Leoben 10 Compute Nodes: p55a 2 x Power 5+ Quadcore, 32 Gbyte RAM/Node Slide 25

26 MU Leoben 12 Compute Nodes: JS22 Blades, Power 6 Quadcore, 16 GB RAM/Node Slide 26

27 Job Management Slide 27

28 Job Management IBM LoadLeveller About 20 users Typically 4 16 cores / job Typical run times: 1 day 1 month Slide 28

29 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 ( 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

30 Organic -Conjugated Molecules Pentacene (C22H14) OFET Organic Field Effect Transistor Para Sexiphenyl (C36H26) 2.6 nm OLED Organic Light Emitting Diode Slide 30

31 Angle-Resolved Photoemission h (21eV) e 6P(20 3) Slide 31

32 Angle-Resolved Photoemission Koller et al., Science 317, 351 (2007). Slide 32

33 Reconstruction of Molecular Orbitals e h (35eV) kx Slide 33

34 exp e h (35eV) DFT HOMO Reconstruction of Molecular Orbitals exp DFT LUMO kx Puschnig et al., Science 326, 702 (2009). Slide 34

35 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

36 Stacking Faults in Steel Reyes Huamantinco, Ruban, Puschnig, Ambrosch Draxl, to be published Slide 36

37 Thank you for your attention! Slide 37