DFT project with BURAI GUI for Quantum ESPRESSO
You will use Quantum Espresso to calculate band structures, DoS and other material properties in this course. You will present a poster in a departmental fail, and submit a written report on the results.
A good place to get extra help is the usage videos at the BuraiWIX Site. Perfer command line flexibility? Go to the github: https://pranabdas.github.io/espresso/
for step by step instructions.
Stepwise PH 575 Guide to Quantum Espresso DFT Caclulations
Below, are the recomeneded steps for your first calculation.
**
For your first time, skip direclty to step 4, and the QuantumEspresso and "practice CIF files" built in. We recommend starting with Si.**
STEP 1: Download and install the crystal information file (CIF) visualization program VESTA
STEP 2:
For calculations on your own material (get instructor approval on your choice), you will need the position of the atoms in your material by finding or making a CIF file.
Find source CIF files of the material you wish to study. We recommend the Materials Project Database(next gen). Search for by elemental compositions e.g. type "Ga-As" or just full formula "GaAs".
Inspect properties, if you are happy with your choice download the CIF file, as shown in the following example for Si.
STEP 3: Open this saved CIF in VESTA (simply file, and the open). Explore your structure. If you are happy with it and no changes needed you must now re-export the CIF file from VESTA (otherwise QuantumEspresso often does not recognize CIF file generated direclty).
Do this by clicking, File, and Export Data... , then choose CIF file type and export (ideally to a named directory in you Burai folder, but it can be anywhere).
If you have trouble see video.
STEP 4: If not done already, Download and install QuantumEspresso + its graphical user interface (GUI) called BURAI. This can be done in one step.
BURAI is open source software GUI that sets up density functional theory (DFT) calculations are perfromed using Quantum Espresso.
BURAI with Quantum Espresso can be download here. (YouTube installation video) [note you MAY need to update/install Java 64-bit to get BURAI.exe to open!]
Basics manuals on using BURAI are here.
STEP 5: Open your VESTA-convered CIF in BURAI. (Click "My Computer" on side-bar and navigate to folder with CIF file and load it. Inspect structure and properties.
If happy, check to see in QunatumEspresso will run an SCF calculation of the energies. See an exanmple "click sequence below".
Problems: Often, there are CIF input file problems (VESTA can fix this), or even new pseudopotentials needed for the calculation (they must be downloaded). Sometime the calculation are too big (e.g. too many atoms per cell, or poorly setup). See an example video (Burai GUI silicon example) to help if lost.. Alternatively, if you hate GUIs, you can do the calculation properly with commannd line code (Si by QuantumEspresso Command lines) or (longer explanation with Fermi energy calculation)/
STEP 6: If successful, iterate the above step 5 process but choose to calculate the Band Structure or DoS (instead of clicking SCF).
Both processes require that your SCF calculation convered before running. In both cases you can adjust the default parameter to check the best ouput (e.g. k-space walk), and also restrict output ranges, etc. if the calculation take too long.
See examples for GaAs below.
STEP 7: Does your reult make sense with literature? E.g. here I go back to the CIF file source for my GaAs structure, https://next-gen.materialsproject.org/materials/mp-2534#properties.
If not, troubleshoot! If generally yes, be sure to export raw data (e.g. open output files in Excel)
For you own calculations, it is best to choose the best symmetry path through k-space. This Brillouin zone database is a useful resource. An example of how to input high-symmetry points k-space walks see video: Choosing and Providing the HIGH SYMMETRY POINTS for BANDSTRUCTURE Calculation - QUANTUM ESPRESSO
Some best-practice output TIPS: Do take a screen shot, but if you plan to put this your report, please try to re-graph in your favorite graphing program (for example here is video of how to plot band structures using OriginLab graphing).
To get raw Band and DoS data, go the file-folder in the Burai directory where it is saved, e.g. I called the above GaAsVESTA, and all output files were saved to C:\Users\grahamat\.burai\GaAsVESTa. The ones you can load in Excel (or notebook) tend to have a *.gnu extension.
STEP 8: Refine and explore futher calculations(e.g. molecular dynamics, phonon, and more). Note, at some point you may want to go back to Qunatum Espresso command-line code, the GUI (Burai) is limited.
A good example of the "next level" calculations is Fe lattce Bulk Modulus and Equation of State Calculation using Quantum ESPRESSO (for student wishing to "push" this learning towards the next level).
Another example is the getting the DoS associated with each oribital contribution (3s, 3p, 4s, etc), see video example for Aluminum.
STEP 9: Assemble, print and present your poster to the Department. A written report will follow ~1 week later.
Github Command line examples for QE: command line tutorials at the github
Nifty exercise: [calculate graphene DoS]
QE other property tutorials + matplotlib plots:
1. Dielectric constants
2. DFT+ U Hubbard Model Correction
3.
Plot/caculate your own Fermi surface
4. Phonon dispersion
5. Projected DoS (P-DOS)
Other QE courses:
1. CompMatPhys Open Course
2. Don't like Burai? Command line tutorial
("NSF Paradim" command line course)
YouTube Video BURAI GUI Examples:
1) Intro level: DFT and DoS of Graphene Calculation Steps
2) Modertate: DFT and DoS of MoS2 Calculation Steps
3) Advanced: Optical properties, dielectric functions calculations