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The old (pre v1.6.0) KIM API repository. Current development now occurs in the kim-api repo

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# The contents of this file are subject to the terms of the Common Development
# and Distribution License Version 1.0 (the "License").
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# specific language governing permissions and limitations under the License.
# When distributing Covered Code, include this CDDL HEADER in each file and
# include the License file in a prominent location with the name LICENSE.CDDL.
# If applicable, add the following below this CDDL HEADER, with the fields
# enclosed by brackets "[]" replaced with your own identifying information:
# Portions Copyright (c) [yyyy] [name of copyright owner]. All rights reserved.

# Copyright (c) 2013--2014, Regents of the University of Minnesota.
# All rights reserved.
# Contributors:
#    Ryan S. Elliott
#    Ellad B. Tadmor
#    Valeriu Smirichinski

# Release: This file is part of the openkim-api.git repository.

============================= The KMI API package =============================

This file provides an introduction to the KIM API package.  This is the first
file that you should read after unpacking the package.


Atomistic or molecular simulations of materials have the potential to play a
key role in the development of innovative technology to address many problems
the world is currently facing (including climate change, energy generation and
distribution, and terrorism).  Recent examples, where valuable contributions
and greater insight have been obtained, include applications in chemistry and
organic chemistry, nanoindentation and tribology, materials processing and
properties, and nanotechnology and nanofluidics.  To model the large numbers of
atoms required for many applications, and to be able to study their dynamics
over reasonable time scales, it is generally necessary to develop approximate
models of interatomic bonding, referred to as "interatomic potentials" or
"interatomic models".  Once such a model is at hand, one can in principle
predict almost any mechanical property (and some thermal properties) of the
element (or elements) it purports to describe.  Generally, these models define
the forces and energies used for sophisticated simulations using methodologies
such as molecular dynamics, Monte Carlo, lattice dynamics free energy methods,
and multiscale methods. From such simulations, complex material properties and
phenomena can be extracted, including such things as melting temperatures,
solid-liquid interface phenomena, fracture properties, and dislocation
nucleation and motion.

This software package is an implementation of the application programming
interface (API) standard for interatomic models being developed as part of the
Knowledgebase of Interatomic Models (KIM) project.  KIM ( is
a current initiative to develop and implement standards for the atomistic
simulation of materials.  The effort aims to help bring order to the efforts of
the education, research, and industrial communities and to make it easier for
new (and existing) scientists to leverage the work of others in this important
field.  The KIM project has several main objectives:

1. Development of an online open resource for standardized testing and
   long-term warehousing of interatomic models (potentials and force fields)
   and data.

2. Development of an API standard for atomistic simulations, which will allow
   any interatomic model to work seamlessly with any atomistic simulation code.

3. Fostering the development of a quantitative theory of transferability of
   interatomic models to provide guidance for selecting application-appropriate
   models based on rigorous criteria, and error bounds on results.

4. Striving for the permanence of the KIM project, including development of a
   sustainability plan, and establishment of a long-term home for its content.


The KIM API package aims to give computer programmers the ability to write
atomistic or molecular simulation programs and routines capable of seamlessly
interfacing and interacting with other programs and routines, regardless of the
programming language (C, C++, FORTRAN 77, Fortran 90/95/2003, Python, etc.) in
which the codes are written.

This version of the KIM API package is distributed under the CDDL Open Source

The current version of the KIM API package supports the following features:

* Currently supported programming languages:
  C, C++, FORTRAN 77, Fortran 90/95, Fortran 2003.

* Support for static and dynamic linking of programs using the KIM API

* Support for automatic translation between zero-based lists (C-style numbering
  beginning with 0) and one-based lists (Fortran-style numbering beginning
  with 1)

* Communication of an arbitrary number of `arguments' between a `Model'
  (interatomic potential) and a `Test' (simulation code that uses a Model).
  This is facilitated by the use of `KIM descriptor files' (whose names end
  with a `.kim' extension) and a single KIM API object data structure that
  stores all information to be communicated between a Model and a Test.

* Data types: integer, float, double, method (for exchanging pointers to
              functions), pointer (for exchanging "everything else").  Each of
              these data types can be use to create multi-dimensional array
              `arguments' that are exchanged between Models and Tests.

     Currently, the KIM API does not define any (more complex) data structures.
     However, in the future (as the need arises, and in consultation with the
     atomistic and molecular simulation community) additional data types and
     data structures may be introduced.

* Physical Units: The KIM API supports the specification of physical units for
  each `argument' exchanged between a Model and Test.  A Model is either
  `fixed' or `flexible' with regard to units.  `fixed' means it is unable to
  convert to a different set of units.  `flexible' means it can convert its
  values to the Test's units.

* Neighbor lists and Boundary Conditions (NBC) methods: To facilitate
  computational efficiency, the KIM API defines a number of standard methods by
  which a Test may provide a Model with information about the neighbors of each
  atom in a configuration.  These currently include options that allow for
  common techniques, such as the use of the `minimum image' convention for
  orthogonal periodic boundary conditions, `padding atoms', and neighbor lists
  with relative position vectors.

* Neighbor list routines are expected to be provided by the calling Test.  The
  API provides support for `Locator' and `Iterator' neighbor list modes.  (A
  `Locator' returns the list of neighbors of a specified atom.  An `Iterator'
  works by incrementing an atom counter and returning the identity of the next
  atom (i.e. its number) and its neighbors.)  The API also supports half
  (symmetric and unsymmetric) and full neighbor lists.

* Particle Species: The KIM API provides the ability to designate the physical
  species (or, more generally, type) of each particle in a simulation.
  Currently, only one identifier is provided for each element in the periodic
  table.  In the future support for Models such as CHARMM and similar
  force-fields will be added.

* Model Parameters: The OpenKIM philosophy views a `Model' as a well-defined
  computational code that includes fixed specific values for all parameters
  needed to perform an actual computation.  However, it is often useful to
  explore how a Model's predictions vary as the values of its parameters are
  varied.  For this reason, the KIM API provides the ability for a Model to
  `publish' its parameters so that a Test may modify them during the course of
  a simulation.

* Model Drivers: The KIM API package provides the ability to create Model
  Driver routines.  A Model for a given material can be created from a Model
  Driver by providing a file or files with the appropriate parameter values for
  the material of interest.

For more information on all of the above, see the files in the DOCs directory
described below.  Features planned for future releases are described in the
TODO file in this directory.  (See list of directory contents below.)

Your next step after reading this file is to install the KIM API package.  See
the detailed instructions in the INSTALL file in this directory.


This directory (by default, openkim-api-vX.X.X) contains the following files
and directories:

     list of main changes made to each API release

     documentation directory.  This directory contains the file
     openkim-api-vX.X.X-introduction.pdf which provides an overview of this
     release of the KIM API package, links to the files
     KIM_API_Descriptions.txt and, and a TEMPLATES directory
     containing template files for creating your own KIM Models.  (See the
     README file in that directory.)

     directory containing examples of interatomic Model Drivers, Models, and

     detailed instructions on how to install the KIM API package

     directory containing the KIM API service routines

     The Common Development and Distribution License (CDDL) Version 1.0 file

     directory containing the common Makefiles and default settings used by the
     KIM API package make system.

     Each Model is stored in its own directory.  This is where you should place
     Model directories downloaded from  (Or use `make
     examples' to copy the example Models to this directory.)

     Each Model Driver is stored in its own directory.  This is where you
     should place Model Driver directories downloaded from
     (Or use `make examples' to copy the example Model Drivers to this

     make file for compiling the KIM API services routines and example Tests
     and Models.

     Example Makefile.KIM_Config file.  This file provides the basic settings
     needed to compile the KIM API system and associated Model Drivers, Models,
     and Tests.

     This file.

     Each Test is stored in its own directory.  This is where you should place
     Test directories downloaded from  (Or use `make
     examples' to copy the example Tests to this directory.)

     A file listing features planed for future releases of the KIM API



If you have problems or questions, send an email with your question and all
relevant information to

The members of the openkim development team actively monitor this email list
and will do their best to help you with your question in a timely fashion.

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