QE_Lecture1_Intro_25

Quantum ESPRESSO course for solid-state physics
1. Introduction to DFT with QE

Transcript

1. Quantum ESPRESSO course for solid-state physics Nguyen Tuan Hung FRIS, Tohoku University https://nguyen-group.github.io/ 1. Introduction to DFT with QE
2. What & Why DFT? Density-functional theory (DFT) Electron density n(r) Functional = function of function Energy[electron-density] E[n(r)] HΨ = E[n(r)]Ψ Nature Reviews Materials 1, 15004 (2016) DFT can predict the properties of materials without any experiment →Designing new materials →Understanding materials →Reduce experimental costs 2
3. Impact of DFT THE TOP 10 PAPERS: 2 papers on density-functional theory (DFT) in the top 10 most cited papers in the entire scientific literature, ever. NATURE, OCT 2014 3
4. 130,981 citations (2023) GGA made the DFT possible for practice. Red colors are papers related to DFT Hohenberg–Kohn theorems Starting point of the concepts of DFT Kohn-Sham equation Numerical codes for DFT is possible 4
5. The original idea of DFT Just store data for Si case: 500084 numbers DFT can reduce dimension of HΨ = EΨ! To make the idea can work → two systems must be equivalent 50003 numbers HΨ = E(Ψ1 , Ψ2 ,… ΨN )Ψ 3N-dimensions HΨ = E[n(r)]Ψ 3-dimensions 5
6. The Hohenberg-Kohn (H-K) theorems The H-K existence theorem The H-K variational theorem • A universal functional for the total energy E[n(r)] can be defined in terms of n(r). The exact ground state energy is the global minimum value of this functional. Density-functional theory E[n(r)] n(r) Electron density Properties ? 6
7. How to Know n(r)? Self‐consistent field (SCF) method The Kohn-Sham equation Exchange-correlation potential The Pauli principle to avoid overlap (exchange - Vx ) Keeping to lower the Coulomb repulsion (correlation - Vc ) (Unknown functional) 7
8. How to deal with unknown functional E[n(r)]? GGA it was a breakthrough- highest citation in APS history, leading to the widespread use of DFT. Errors of atomization energies Local density approximation (LDA) -1980 (GGA) 8
9. Why now? 9 Today, DFT can even run on a mobile Note PC can completely calculate the DFT for practice
10. 10 Many DFT production codes Local orbital basis codes •SIESTA – numerical atom-centered basis pseudopotential code •ATK-DFT – numerical atom-centered basis pseudopotential code (recently acquired by Synopsys-URL will change) •CRYSTAL – gaussian basis all-electron code •AIMPRO •FHI-AIMS – (commerical license) full potential, all-electron, numerical orbitals •FPLO •OpenMX – GPL – numerical atom-centered basis PP code All-electron (augmented methods) codes •ELK – GPL – FP-LAPW •EXCITING – FP-LAPW, focus on excited state properties (TDDFT, MBPT) [license not apparent on website, probably open source] •FLEUR – “freely available” – FLAPW code •RSPt – “Open Source” – FP-LMTO •WIEN2k – modest fee – full potential LAPW • VASP • CASTEP • CPMD • ABINIT – GPL • BigDFT – GPL – wavelets • Quantum-Espresso (formerly PWscf) – GPL • PEtot – GPL • JDFTx – GPL • PARSEC – GPL – real space, pseudopotential • CP2K – GPL (mixed basis DFT) • GPAW – GPL – real-space multigrid PAW code • SPHINX • QBOX – GPL – plane wave pseudopotential, large parallel Plane-wave and related methods
11. Easy to install DFT codes Using a Virtual Machine or Live Linux system for DFT 11 https://quantum-mobile.readthedocs.io/ https://cmsi.github.io/MateriAppsLive/
12. QE is FREE Step 1: Install Ubuntu on Windows store Step 2: Install Quantum ESPRESSO $ sudo apt-get update $ sudo apt-get install quantum-espresso https://atomistic.software/ Free Easy install 12
13. Some features of QE Quantum ESPRESSO is a bundle of codes (DFT and beyond DFT) 13
14. - Book: Quantum Espresso course for solid-state physics - Input & Output files at GitHub: https://github.com/nguyen-group/QE-SSP Materials for class 14
15. Workshops & Tutorials https://www.quantum-espresso.org/schools-workshops-tutorials/ https://www.max-centre.eu/training-events https://pranabdas.github.io/espresso/ Other sources 15 Books