You've activated the antiferromagnetism in-app guide. In this guide, you will learn how to model an antiferromagnetic configuration of CoO and analyze the corresponding PDOS. Note: You should follow the in-app guide on ferromagnetism and DFT+U first.
Click on Step 1: Select structure and follow the instructions to proceed.

Tasks

Antiferromagnetic calculations require to define a starting magnetization with opposite sign for atoms of the same chemical element. In this example, we will consider cobalt oxide (CoO) and the antiferromagnetic moments are on cobalt. However, the unit cell of CoO only has 2 atoms (1 Co and 1 O). Therefore, we need to perform two steps before submission:
  1. Click on the From examples tab
  2. Click on Simple crystals
  3. Select Cobalt oxide from the dropdown list
  4. Click on the Edit structure panel and open the Edit cell tab. Set the matrix element (3, 3) to the value of 2 and click Apply transformation to double the unit cell along the third periodic direction (1 x 1 x 2 supercell). Note: click the Apply transformation button only once! Inspect the structure in the View structure panel and verify that you now have 4 atoms in the unit cell.
  5. Switch to the Edit atom tags tab.
  6. We now want to assign the two Co atoms to two new species Co1 and Co2 (rather than the same Co species). This will allow us, later, to set different starting magnetization for them (e.g. spin down for Co1 and up for Co2).
    • In the 3D structure visualizer, click on the Co atom at the corner of the unit cell to select it: it will turn green. In the Edit atom tags tab, press the From Selection button to automatically insert the index of that atom in the text box. Set the tag to the value 1 and press the Update tags button to apply the change: now atom will be assigned to species Co1.
    • Repeat the previous step for spin-up, but this time, select the other Co atom and set the tag to 2.
  7. In order to double check the tags that you assigned, you can type “1..4” in the “Index of atoms” textbox to show all four atoms. You should verify that the two Co atoms have different tags, while oxygens have no tag. (Note that the table is scrollable, by default you see only the first few rows).
  8. Click on the Confirm button to proceed

Tasks

  1. Select Structure as is (in the interest of time, we skip the relaxation here)
  2. Open step 2.1 for further instructions
Here we select the properties to calculate. Each property is associated with a workflow that will submit one or more calculations. In this guide, you will calculate and analyze the PDOS. In this way, you can easily verify that you have indeed modeled an antiferromagnetic configuration.

Tasks

  1. Check (activate) Electronic projected density of states (PDOS)
  2. Open step 2.2 for further instructions
Note: If running locally (for example, on the AiiDAlab demo server), we recommend selecting the fast protocol to reduce the computational cost.

Tasks

  1. Select the fast protocol
  2. Set Magnetism to On. Keep the Electronic type as metal (this is required since we want to determine the magnetization self-consistently. When setting to insulator, the app will inform you that this is only possible for claculations for which you fix the total magnetization of the unit cell.).
  3. Open the Advanced settings panel to set the initial magnetic moments.
Here, we will define the initial magnetic moments.

Tasks

  1. Similar to what has been done for the ferromagnetic case, we will set the initial magnetic moments in the Magnetization subsection. However, in this case we assign opposite starting magnetization to Co1 and Co2.
  2. Set the ones for Co1 to -3 μB, Co2 to 3 μB and O to 0.6 μB
  3. In this guide, we do not activate the Hubbard U. However, feel free to do it as another post-guide exercise to investigate the effect of the Hubbard U on the antiferromagnetic electronic structure.
  4. Switch to the PDOS tab for some final fine-tuning

Tasks

  1. Set Energy grid step (eV) to 0.03 eV. We change this parameter here to reduce the computational costs.
  2. Click the Confirm button to proceed

In the submission step, we define the computational resources to be used in the calculations. The global resources are used to define resources across all workflow calculations. Optionally, you can override the resource settings for specific calculations.

Warning: If running locally (for example, on the AiiDAlab demo server), we recommend keeping nodes and CPUs at the default minimum of 1 each.

Once the resources are defined, we can optionally customize the workflow label (pre-filled according to the settings of steps 1 & 2), as well as provide a detailed description of the workflow. Once we are ready, we can submit the workflow. You first need to select which code (code executable + computer where this will run) to use for each step of the workflow. The Quantum ESPRESSO app should always install a local Quantum ESPRESSO executable that is sufficient for this tutorial, but you can setup additional codes installed on remote supercomputers. For more information on how to set up codes, please refer to the corresponding documentation.

Tasks

  1. Check that the the default options in the "Global resources" panel are the expected ones. Specifically: select 1 node and 1 CPU for each of the codes. Unless you want to run elsewhere, use the default codes on the AiiDAlab server (ending with `@localhost`) that are available from the dropdown menus.
  2. (Optional) customize the workflow label
  3. (Optional) add a workflow description
  4. Click the Submit button to proceed
Warning: The workflow may take a moment to submit.
Here in the results panel, each tab will open results pertaining to a specific calculation submitted by the workflow.
See further instructions below in the Electronice PDOS tab.
When results are available, the Load results button will become active allowing us to load the results from AiiDA.

Tasks

  1. Once the calculation is complete, click on the Load results button to load the available results
  2. Select Group by angular momentum in Orbital grouping.
  3. Find the location of the O-2s states. You already learned how to select and focus on the different contributions by double-clicking on the legend. If you do not immediately find these states, remember that you can also click on the x-axis and drag it to change the displayed energy range.

Post-guide exercises

  1. Use the app to compute the antiferromagnetic band structure.
    • Follow the same steps as before, but this time, select the electronic band structure in the Configure workflow panel.
    • You can also check both boxes to calculate the PDOS and band structure (and, in the advanced band structure options, turn on Fat bands). This will allow you to plot so called fat-bands, showing the orbital character of the bands.
  2. Compare the antiferromagnetic results with the ferromagnetic example discussed in the corresponding Ferromagnetism & DFT+U in-app guide.
    • This time, you do not need to set the tags.
    • Set the initial magnetic moments to the same values as before.
    • Finally, compare your FM PDOS with the AFM one obtained before.
  3. As mentioned in the Advanced settings, consider to rerun the antiferromagnetic PDOS with a Hubbard U correction to see how the electronic structure changes in case of the antiferromagnetic configuration.
We already provide some of these results in our examples. Check the Download examples on the landing page of the app. You can follow the instructions there to import the examples. Afterwards, you can inspect the results in your Calculation history.