QE-SSP_Lecture_1_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. Applications: Searching thermoelectric materials Without experimental parameters 1D CNTs Nguyen et al., Phys. Rev. B 92, 165426 (2015) 2D InSe 2D tetradymites Nguyen et al., Nano Energy 58, 743- 749 (2019) Density functional theory (DFT) HΨ = EΨ Semimetal Nguyen et al., Phys. Rev. B 105, 115142 (2022) Nguyen, Appl. Phys. Lett. 123 (2023) Nguyen et al., Appl. Phys. Lett. 111, 092107 (2017) Nguyen, J. Appl. Phys. 125, 082502 (2019) 7/25
10. Applications: Second-harmonic generation (SHG) Threefold enhancement of SHG in 2D Janus materials マイナビ : “東北大、ヤヌス型は通常のTMDよりも第2高調波が3倍以上増強することを確認” Nguyen et al., ACS Nano 17, 19877 (2023) 10
11. Applications: Lithium-ion battery Q. D. Truong, L. C. Yin, N. T. Hung, et al., Electrochim. Acta 332, 135218 (2020). 11 N. T. Hung et al., J. Phys. Chem. C 123, 30856 (2019)
12. Applications: Designing 3D Carbon materials Archimedean lattice New 3D Carbon networks N. T. Hung, et al., Carbon 125, 472-479 (2017). 12
13. Applications: Designing photocatalyst materials Successful synthesis of γ-GeSe (Nano Lett. 21, 4305, 2021) New Janus 2D γ-Ge2SSe V. V. Thanh, D. V. Truong and N. T. Hung, ACS Appl. Energy Mater. 6, 910-919 (2023). High-performance material for photocatalysis and thermoelectricity Repalce Se atom to S atom 13 Janus god
14. Applications: Understading Raman spectra S. Han, Y. Zhao, N. T. Hung, et al., J. Phys. Chem. Lett. 13, 1241–1248 (2022) Helicity-changing Raman spectra of black phosphorus under circularly polarized light Complex Raman tensor (Experiment can not observer) Experiment Theory 14
15. Applications: Understading optical spectra D. P. Gulo, N. T. Hung, et al., Carbon 197, 485-493 (2022) Question from experimentalist: WHY? Answer from DFT: Plasmon-assisted optical absorption Can explain by standard theory: Higher T --> higher lifetime of electron Can not explain why optical absorption is higher with higher T? Silicon Graphite The limit of experiment is not easy to increase photon energy. Plasmon signal But easy in DFT 15
16. Applications: Understading exciton effect D. P. Gulo, N. T. Hung, et al., Phys. Rev. Mater. 7, 044001-1-13 (2023) Well-known from previous works New phase (semimetal) Orgin of peaks come from excition or not? ➢ IPA: independent particle approximation (not considering exciton effect) ➢ BSE: Bethe-Salpeter equation (including exciton effect Experiment is not easy to distinguish physical phenomena, but in DFT, we can do that. exciton no exciton 16
17. Why now? 17 Today, DFT can even run on a mobile Note PC can completely calculate the DFT for practice @NCCR MARVEL
18. 18 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
19. Easy to install DFT codes Using a Virtual Machine or Live Linux system for DFT 19 https://quantum-mobile.readthedocs.io/ https://cmsi.github.io/MateriAppsLive/
20. 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 20
21. Some features of QE Quantum ESPRESSO is a bundle of codes (DFT and beyond DFT) 21
22. - Book: Quantum Espresso course for solid-state physics - Input & Output files at GitHub: https://github.com/nguyen-group/QE-SSP Materials for class 22
23. Workshops & Tutorials https://www.quantum-espresso.org/schools-workshops-tutorials/ https://www.max-centre.eu/training-events https://pranabdas.github.io/espresso/ Other sources 23 Books