Frequently Asked Questions (FAQ)
This page contains answers to common questions about the Materials Project.
See also our "Glossary of Terms" page which defines common terms in use by Materials Project.
You can login to the Materials Project either using an existing social identity provider (currently GitHub, Google, Facebook, Microsoft or Amazon) or via an email link.
- I want to log in with my social identity provider (GitHub/Google/Facebook/Microsoft/Amazon), but I can’t.Ensure that your password for your provider is correct (go to their site and log in there), ensure that you have a full name set on that account, and ensure that you allow Materials Project to see your basic profile info (name and email address).You also may be behind a firewall that doesn’t allow GitHub/Google/Facebook/Microsoft/Amazon. In that case, use our email based option instead.
- I appear to sign in OK (the popup goes away), but then I remain on the sign-in screen.It may take a few seconds, depending on your connection, to actually get logged in. This is because we have an external identity provider verify your email address so that we don’t have to store any passwords on our servers.You may also have an older browser that won’t work well with our website at all. The latest version of Mozilla Firefox, Google Chrome, or Microsoft Edge will work well. Older versions of Internet Explorer will not work.
- I tried using the email option several times but haven’t received a login link.There is a known issue with Tencent @qq.com addresses, where Tencent throttles delivery and you might not get an email within a reasonable amount of time. Please consider using an alternative to your @qq.com address for login.
Citations are appropriate wherever Materials Project data, methods or output are used. See this page on the Materials Project website for more information:
There is a canonical Materials Project citation, and additional citations for specific properties or tools. See also the Database Versions page for information on how to cite a specific database version.
The Materials Project core data is all calculated in-house by the Materials Project team using a variety of simulation methods. To understand the quality of these predictions, it is crucial to read the peer-reviewed publications from the Materials Project where each property is benchmarked as much as possible against known experimental values: this will give an estimate of typical error and, importantly, any systematic error that may be present.
The same crystal structure can have multiple, equivalent sets of lattice parameters depending on what crystallographic "setting" is used.
Typically, there are two sets of lattice parameters reported. Lattice parameters can be defined for the primitive cell, which is a definition of the crystal with the fewest number of atoms and therefore convenient for simulations and other uses, and the conventional cell, which is typically easier to visualize and more like you will see in textbooks.
If the lattice parameters are very different to what you expect, check the setting first!
Some systematic errors are also present. These will typically be an over-estimation of 1–3% for most crystals. Layered crystals will also typically have significant error in the interlayer distances since van der Waals interactions are not well-described by the simulation methods (PBE) used by Materials Project. These systematic errors will be improved as Materials Project switches to user newer simulation methods (r2SCAN). See Calculation Details for more information.
Electronic band gaps are difficult to calculate reliably from first principles, especially using methods that scale well to hundreds of thousands of materials. The method used by the Materials Project (PBE) systematically underestimates band gaps.
While it would be possible to provide higher quality calculations for a select number of materials, with more accurate band gaps, it is noted that for materials discovery purposes it is useful to have a dataset that has the same systematic error. See Electronic Structure for more information.
The Materials Project presents the data it generates in two ways:
- 1.As individual calculations. These are always the same, and as far as possible Materials Project tries to ensure all historical calculations remain available. Typically, only advanced users will access information about individual calculations.
- 2.As aggregated information. This is information generated from a combination of individual calculations. This information is what is presented on the public "material details" pages, and is what most users will access. As new, improved calculations are performed, this aggregated information can change.
Every database needs a unique key which can be used to distinguish one entry from another. In the Materials Project, each unique material is given a
material_id(also referred to in various places as mp-id, mpid, MPID). This allows a specific polymorph of a given material to be referenced. For example, wurtzite GaN is assigned the
mp-804, while zinc blende GaN is assigned a
The Materials Project is a computational resource. All of the information on a given material details page is actually a combination of data generated from many individual calculations or "tasks". It is also important that these tasks also have unique identifiers.
When a task is added to the Materials Project database, it will get an identifier assigned with the format
mp-[0-9]("mp-" with numbers after it). These identifiers are assigned sequentially, so smaller numbers usually refer to older calculations. An identifier referring to an individual calculation task are known as a
When the Materials Project database is built, a unique material will then have a collection of multiple different task_ids associated with it. The numerically smallest
task_idwill then become the
material_id. This ensures that, as new, additional calculations are associated with the same material, its
material_idshould not change.
Some calculation tasks were associated with a search for multivalent cathode materials. These tasks were given the prefix
mp-and thus some materials also had the prefix
mvc-. However, this caused confusion and this approach has been retired. Tasks with the prefix
mvc-still exist since the
task_idcannot change, but a
material_idwill now always start with an
mp-prefix by convention provided that at least one task associated with that material has the
task_idwill never change. It will always refer to the same, individual calculation task.
material_idmight change in rare instances, such as the removal of the
mvc-prefix, although this is avoided wherever possible.
material_iddoes change, we ensure a redirect on the website is always in place, and the new
material_idcan also be found programmatically with the API using the
get_material_id_from_task_id()function. This way, any publications or research that reference an older
material_idare still valid, and the relevant data can still be retrieved.
Consult our glossary here: