Phase Diagrams

Tutorial Created with Software Release: 2025-1
Topics: Energy Capture & Storage, Thin Film Processing
Methodology: Periodic Quantum Mechanics
Products Used: MS Maestro, Quantum Espresso

Tutorial files

74 KB
This tutorial is written for use with a 3-button mouse with a scroll wheel.
Words found in the Glossary of Terms are shown like this: Workspacethe 3D display area in the center of the main window, where molecular structures are displayed

 

Tip: You can hover over a glossary term to display its definition. You can click on an image to expand it in the page.
Abstract:

 

In this tutorial, we will plot phase diagrams for a two- and three-component system.

 

Tutorial Content

  1. Introduction to Phase Diagrams

  1. Creating Projects and Importing Structures

  1. Creating a Phase Diagram for a Two-Component System

  1. Creating a Phase Diagram for a Three-Component System

  1. Conclusion and References

  1. Glossary of Terms

1. Introduction to Phase Diagrams

Phase diagrams are graphical representations of multi-component systems' phase equilibria under constant temperature and pressure. In multi-component systems, phase boundaries highlight where phases coexist, which aids in predicting which phases will remain stable over a wide variety of conditions. It exhibits composition-dependent transformations at constant temperature or pressure, which is useful in the design and production of multi-element materials. Phase diagrams aid in forecasting reaction paths and transformation sequences as the material is processed or environmental conditions change.

In this tutorial, we consider a special type of phase diagram - the compositional phase diagram, that reflects relative stability of compounds with respect to their composition. For example, binary compounds AxB1-x generally have different stability at various compositions x. The stability is usually measured as a free energy per atom. This energy can be predicted by calculations of free energies of relevant compounds that can be performed using density functional theory (DFT) with various degrees of approximation.     

In this tutorial, the Phase Diagram Viewer panel will be used to plot the compositional phase diagram for a two-component (LiO) and three-component (LiCoO) system.

This tutorial does not cover obtaining the LiO and LiCoO energy values to produce the phase diagrams plots. These energy values can either be calculated or imported from other sources (such as The Materials Project) into Materials Science (MS) Maestro. See the Electronic Structure Calculations of Bulk Crystals Using Quantum ESPRESSO tutorial for steps on how to calculate Quantum ESPRESSO (QE) energy values.

2. Creating Projects and Importing Structures

At the start of the session, change the file path to your chosen Working Directorythe location where files are saved in MS Maestro to make file navigation easier. Each session in MS Maestro begins with a default Scratch Projecta temporary project in which work is not saved, closing a scratch project removes all current work and begins a new scratch project, which is not saved. A MS Maestro project stores all your data and has a .prj extension. A project may contain numerous entries corresponding to imported structures, as well as the output of modeling-related tasks. Once a project is saved, the project is automatically saved each time a change is made.

Structures can be built in MS Maestro or can be imported using File > Import Structures (or drag-and-dropped), and are added to the Entry Lista simplified view of the Project Table that allows you to perform basic operations such as selection and inclusion and Project Tabledisplays the contents of a project and is also an interface for performing operations on selected entries, viewing properties, and organizing structures and data. The Entry Lista simplified view of the Project Table that allows you to perform basic operations such as selection and inclusion is located to the left of the Workspacethe 3D display area in the center of the main window, where molecular structures are displayed. The Project Tabledisplays the contents of a project and is also an interface for performing operations on selected entries, viewing properties, and organizing structures and data can be accessed by Ctrl+T (Cmd+T) or Window > Project Table if you would like to see an expanded view of your project data.

  1. Double-click the Materials Science icon

Figure 2-1. Change Working Directory option.

  1. Go to File > Change Working Directory
  2. Find your directory, and click Choose
  3. Pre-generated files are included for running jobs or examining output. Download the zip file here: schrodinger.com/sites/default/files/s3/release/current/Tutorials/zip/phase_diagrams.zip
  4. After downloading the zip file, unzip the contents in your Working Directorythe location where files are saved for ease of access throughout the tutorial

Figure 2-2. Save Project panel.

  1. Go to File > Save Project As
  2. Change the File name to phase_diagram_tutorial, click Save
    • The project is now named phase_diagram_tutorial.prj

Figure 2-3. The entry list after importing.

  1. Go to  File > Import Structures
  2. Navigate to where you saved the tutorial files and Open inputs.maegz
    • A new entry group has been imported that contains 2 subgroups: Li-O and Li-Co-O. All entries are selected(1) the atoms are chosen in the Workspace. These atoms are referred to as "the selection" or "the atom selection". Workspace operations are performed on the selected atoms. (2) The entry is chosen in the Entry List (and Project Table) and the row for the entry is highlighted. Project operations are performed on all selected entries and the first entry from Li-O is includedthe entry is represented in the Workspace, the circle in the In column is blue in the Workspacethe 3D display area in the center of the main window, where molecular structures are displayed

Note: Please refer to the Glossary of Terms for the difference between includedthe entry is represented in the Workspace, the circle in the In column is blue and selected(1) the atoms are chosen in the Workspace. These atoms are referred to as "the selection" or "the atom selection". Workspace operations are performed on the selected atoms. (2) The entry is chosen in the Entry List (and Project Table) and the row for the entry is highlighted. Project operations are performed on all selected entries.

These structures can be downloaded from the The Materials Project or imported using the Query Materials Project Database panel. All 123 entries have a provided energy (Etot) value associated with them. The project table () can be used to view the energy values. 49 of these entries are various LixOy compounds and 74 entries are LixCoyOZ compounds with a range of x, y, and z compositions.

3. Creating a Phase Diagram for a Two-Component System

In this section, we will plot a phase diagram for a two-component system, LiO.

Figure 3-1. Opening the Phase Diagram Viewer panel.

  1. With the Li-O entry subgroup selected(1) the atoms are chosen in the Workspace. These atoms are referred to as "the selection" or "the atom selection". Workspace operations are performed on the selected atoms. (2) The entry is chosen in the Entry List (and Project Table) and the row for the entry is highlighted. Project operations are performed on all selected entries in the entry lista simplified view of the Project Table that allows you to perform basic operations such as selection and inclusion, go to Tasks > Materials > Quantum Mechanics > Quantum ESPRESSO > Phase Diagram Viewer

Figure 3-2. Plotting the LiO phase diagram.

  1. Click Load Selected Entries
  2. Select eV for the Energy units
  3. Click Plot

The predicted convex hull of Li-O has been plotted in the panel. Click any entry to display its chemical composition in the plot. Alternatively, click on any data point (green dots or red squares) to view the corresponding compound legend.

Feel free to adjust the unstable cutoff value to see how the plot changes. The line in the diagram represents the convex hull -  the line in the compositional phase diagram connecting the lowest energy systems at each composition. The dots on the convex hull are highlighted green, while the less stable systems are highlighted red. The larger the energy above the convex hull - the less stable the system. The “unstable cutoff” value represents the maximum energy above hull to be included into the phase diagram plot.  

See References for comparison to other predicted Li-O convex hulls.

4. Creating a Phase Diagram for a Three-Component System

In this section, we will plot a phase diagram for a three-component system, LiCoO.

Figure 4-1. Resetting the Phase Diagram Viewer panel.

  1. Reset () the Phase Diagram Viewer panel
  2. Select the Li-Co-O subgroup entry in the entry lista simplified view of the Project Table that allows you to perform basic operations such as selection and inclusion

Figure 4-2. Plotting the LiCoO phase diagram.

  1. Click Load Selected Entries
  2. Select eV for the Energy units
  3. Click Plot

The predicted phase diagram of Li-Co-O has been plotted in the panel. Feel free to adjust the unstable cutoff value to see how the plot changes.

See References for comparison to other predicted Li-Co-O phase diagrams.

Increasing the unstable cutoff value

5. Conclusion and References

In this tutorial, we learned how to create phase diagrams for a two- and three-component system.

For further learning:

For introductory content, focused on navigating the Schrödinger Materials Science interface, an Introduction to Materials Science Maestro tutorial is available. Please visit the materials science training website for access to 70+ tutorials. For scientific inquiries or technical troubleshooting, submit a ticket to our Technical Support Scientists at help@schrodinger.com.

For self-paced, asynchronous, online courses in Materials Science modeling, including access to Schrödinger software, please visit the Schrödinger Online Learning portal on our website.

For some related practice, proceed to explore other relevant tutorials:

For further reading:

6. Glossary of Terms

Entry List - a simplified view of the Project Table that allows you to perform basic operations such as selection and inclusion

Included - the entry is represented in the Workspace, the circle in the In column is blue

Project Table - displays the contents of a project and is also an interface for performing operations on selected entries, viewing properties, and organizing structures and data

Recent actions - This is a list of your recent actions, which you can use to reopen a panel, displayed below the Browse row. (Right-click to delete.)

Scratch Project - a temporary project in which work is not saved, closing a scratch project removes all current work and begins a new scratch project

Selected - (1) the atoms are chosen in the Workspace. These atoms are referred to as "the selection" or "the atom selection". Workspace operations are performed on the selected atoms. (2) The entry is chosen in the Entry List (and Project Table) and the row for the entry is highlighted. Project operations are performed on all selected entries

Working Directory - the location where files are saved

Workspace - the 3D display area in the center of the main window, where molecular structures are displayed