OpenKIM is a major open source effort funded by the NSF to develop standards and improve the reliability of molecular simulations.
The OpenKIM Repository contains computer implementations of interatomic models (potentials and force fields), simulation codes (called "tests") that compute different material properties, and first-principles/experimental reference data. Whenever a new model is added to the system, it is automatically coupled with all compatible tests, and similarly any new test is automatically coupled with all compatible models. The test results obtained in this fashion are inserted into the OpenKIM Repository, where they can be visualized and compared with other test results and reference data. This allows users to select and download appropriate models for their application. Models that are compatible with the KIM Application Programming Interface (API) can be used seamlessly with several major simulation codes that support the KIM API.
This document briefly describes the main OpenKIM features and capabilities and points to more information on how to use them. This is a good place to start if you are new to KIM (or need a reminder on how to do something).
The OpenKIM Repository provides permanent archival storage of interatomic models, tests for computing material properties, reference data, and model predictions (test results). (For details, see the types of KIM content.) Best practice revision and provenance control are employed to ensure content integrity.
Each KIM Item is associated with a
KIM Item Page (KIM Model Page, KIM Test Page, etc.), which provides
information on the item, simulation results, associated files, and a Wiki
where contributors and users can comment on the item. See for example,
the Model Page for the Stillinger-Weber potential.
Each KIM Item is
identified by a unique, permanent
KIM ID of the following form:
CC denotes the item type,
DDDDDDDDDDDDD is a 12-digit code, and
VVV is a version number.
(For details, see the Guide to KIM IDs.)
KIM IDs can be cited in publications (see details
here) and can be linked to from workflow tools,
making it possible for simulations to be reproduced in the future.
The OpenKIM Repository is designed to be user-extendable. Contributions of new Models, Tests, Verification Checks, Reference Data, and Visualizers are welcome. See instructions on adding new content to KIM.
Interatomic models stored in the OpenKIM Repository are exhaustively tested providing users with a wealth of information to help them select a suitable model for a given application.
Each Model is subjected to a series of
Verification Checks evaluating
its integrity, e.g. Are the forces returned by the model consistent
with those obtained through numerical differentiation of the energy? Does the
model have continuous energy and derivatives at its cutoff? and so on.
The Model is graded on each Verification Check and the results are presented
in a dashboard on its Model Page. To learn more, see About Verification Checks.
The OpenKIM Repository contains
KIM Tests uploaded by researchers that
compute material properties of interest (such as equilibrium crystal structures,
elastic constants, surface energies, thermal properties, etc.). The Tests are
applied to all compatible interatomic models in the repository. The results are
stored and can be examined and compared using
visualization tools and text-based tools.
Timing information is also provided so that the relative expense of different
Models for the same computation can be assessed.
OpenKIM provides a framework for researchers to distribute and realize their
molecular simulations research broadly. It is the aim of the KIM project
KIM Tests to become standard, citeable methods for computing
important material properties. A great deal of expertise is required to
compute material properties rigorously and robustly. For more information on KIM Tests and to learn how you can work with the KIM Team on adapting your simulations and expertise to craft a new test, see the Introduction to KIM Tests.
An important part of the KIM Project is the creation of an Application
Programming Interface (API) for molecular simulations. The
is a standard for exchanging information between simulation codes and
interatomic models. Simulators and models that conform to the KIM API
work together seamlessly (much like a DVD and a DVD player).
This means that you can download any KIM Model and use it in any
"KIM-Compliant" simulation code that supports the KIM API;
see here for the current list.
For interatomic models archived in openkim.org that conform to the KIM API
KIM Models), the site stores the actual computer implementation
of the model and not only parameter files that are read in by other
programs. This is important since in some cases the same parameter
file can lead to different results when read in by different programs.
(For a discussion of this effect for tabulated EAM potentials, see
To use KIM-Compliant software, you first need to install the KIM API. Installation from source as well as using binary package managers is possible. See detailed instructions on how to install the KIM API, how to download and install KIM Models, and how to use them with KIM-compliant simulators.
OpenKIM provides a framework for interatomic model developers to distribute their interatomic models in a secure fashion. By conforming to the KIM API, the developers will make their models available at once to a large number of simulation codes.
If you are still not a member, we encourage you to sign up. Becoming a KIM member is free and allows you to vote on important issues related to the project and its administration. For more information, see benefits of membership. Note that you do not need to be a member to access the KIM content.
Support is always available by sending an email with a question and all relevant information to
The message will be posted to the openkim google group:
Members of the OpenKIM development team actively monitor this forum and will do their best to respond to questions in a timely fashion. This forum is also used to announce minor new releases and bug fixes.