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### pair_style kim command

Syntax:

    pair_style kim virialmode model

- virialmode = KIMvirial or LAMMPSvirial
- model = name of KIM model (potential)

Examples:

    pair_style kim KIMvirial model_Ar_P_Morse
    pair_coeff * * Ar Ar

Description:

This pair style is a wrapper on the Knowledge Base for Interatomic Models (KIM) repository of interatomic potentials, so that they can be used by LAMMPS scripts.

In KIM lingo, a potential is a "model" and a model contains both the analytic formulas that define the potential as well as the parameters needed to run it for one or more materials, including coefficients and cutoffs.

The argument virialmode determines how the global virial is calculated. If KIMvirial is specified, the KIM model performs the global virial calculation. If LAMMPSvirial is specified, LAMMPS computes the global virial using its fdotr mechanism.

The argument model is the name of the KIM model for a specific potential as KIM defines it. In principle, LAMMPS can invoke any KIM model. You should get an error or warning message from either LAMMPS or KIM if there is an incompatibility.

Only a single pair_coeff command is used with the kim style which specifies the mapping of LAMMPS atom types to KIM elements. This is done by specifying N additional arguments after the * * in the pair_coeff command, where N is the number of LAMMPS atom types:

- N element names = mapping of KIM elements to atom types

As an example, imagine the KIM model supports Si and C atoms. If your LAMMPS simulation has 4 atom types and you want the 1st 3 to be Si, and the 4th to be C, you would use the following pair_coeff command:

    pair_coeff * * Si Si Si C

The 1st 2 arguments must be * * so as to span all LAMMPS atom types. The first three Si arguments map LAMMPS atom types 1,2,3 to Si as defined within KIM. The final C argument maps LAMMPS atom type 4 to C as defined within KIM. If a mapping value is specified as NULL, the mapping is not performed. This can only be used when a kim potential is used as part of the hybrid pair style. The NULL values are placeholders for atom types that will be used with other potentials.

In addition to the usual LAMMPS error messages, the KIM library itself may generate errors, which should be printed to the screen. In this case it is also useful to check the kim.log file for additional error information. This file kim.log should be generated in the same directory where LAMMPS is running.

Here is information on how to build KIM for use with LAMMPS. There is a directory src/KIM/ with an important file in it: Makefile.lammps. When you do 'make yes-kim' LAMMPS will use the settings in src/KIM/Makefile.lammps to find KIM header files and the KIM library itself for linking purposes. Thus, you should ensure Makefile.lammps has the correct settings for your system and your build of KIM.

Consult the KIM documentation for further details on KIM specifics.

OpenKIM is available for download from this site, namely http://openkim.org. The tarball you download is "openkim-api-vX.X.X.tgz", which can be unpacked via

    tar xvfz openkim*tgz

The openkim-api-vX.X.X/DOCS directory has further documentation. For more information on installing KIM and troubleshooting refer to openkim/INSTALL.

Here is a brief summary of how to build KIM:

1. If you have previously used the openkim-api package (versions 1.1.1 or below), it is recommended that you remove all associated environment variables from your environment. (These include, KIM_DIR, KIM_INTEL, KIM_SYSTEM32, KIM_DYNAMIC, KIM_API_DIR, KIM_TESTS_DIR, KIM_MODEL_DRIVERS_DIR, and KIM_MODELS_DIR.) All setting are now specified in the Makefile.KIM_Config file.
2. Set up the Makefile.KIM_Config file

          (a) Copy the file Makefile.KIM_Config.example to Makefile.KIM_Config
              For example, if you untarred the `openkim-api-vX.X.X.tgz' tarball in
              your home directory, you would do:

              % cd $HOME/openkim-api-vX.X.X
              % cp Makefile.KIM_Config.example Makefile.KIM_Config

              The `%' symbol represents the bash sell prompt and should not be typed.

              (Above `vX.X.X' represents the current release number.)

          (b) Edit the file Makefile.KIM_Config and set the appropriate value for the
              KIM_DIR variable.  This must expand to an absolute path.  Using the same
              assumptions as above, this would be

              KIM_DIR = $(HOME)/openkim-api-vX.X.X

          (c) If appropriate, set explicit values for the remaining three
              directories

              KIM_MODEL_DRIVERS_DIR =
              KIM_MODELS_DIR =
              KIM_TESTS_DIR =

              If these lines are commented out, defaults will be provided by the
              openkim-api make system.

          (d) Set the value of KIM_COMPILERSUITE.  Possible values are `GCC' and
              `INTEL'.

              KIM_COMPILERSUITE = GCC

          (e) Set the value of KIM_SYSTEMLINKER. Possible values are `linux',
              `freebsd', and `darwin'.

              KIM_SYSTEMLINKER = linux

          (f) Set the value of KIM_SYSTEMARCH.  Possible values are `32bit' and
              `64bit'.

              KIM_SYSTEMARCH = 64bit

          (g) Set the value of KIM_LINK.  Possible values are `dynamic-load',
              `dynamic-link', and `static-link'.

              KIM_LINK = dynamic-load

              `dynamic-load' is the preferred option. (Unless performance or
              other issues require it, you should use dynamic-load.)
              `dynamic-link' is like `dynamic-load' but does not use the dl.h
              library.  This option requires a more complicated Makefile
              process, but may improve computation time in some instances.
              `static-link' only works with ONE Model and AT MOST ONE Model
              Driver (in order to avoid the possibility of symbol
              clashes).

          (h) Set override values for other variables, if necessary, by
              adding the desired variable name (after the "# overwrite
              default variable values here" line) and filling in appropriate
              values.

              # overwrite default variable values here

              # overwrite default compiler options

              CC =
              CXX =
              FC =

              # overwrite default compiler option flag lists
              FFLAGS   =
              CCFLAGS  =
              CXXFLAGS =
              LDFLAGS  =

              # overwrite default linker options
              LDSHAREDFLAG =
              LINKSONAME =
              LDWHOLEARCHIVESTARTFLAG =
              LDWHOLEARCHIVEENDFLAG =

              # overwrite default install directories
              package_name =
              prefix =
              libdir =

3. In the remainder of the documentation we will use the string $KD to represent the location of the openkim-api source package (the value of the KIM_DIR variable discussed above). If you wish to, type the below commands exactly as written to set the shell variable KD to the appropriate value:

          bash:
          % export KD=$HOME/openkim-api-vX.X.X

4. To compile the package, including the provided examples, change to the $KD directory and execute `make examples' and then `make':

          % cd $KD
          % make examples
          % make

            This builds all Model Drivers, Models, Tests, and the openkim-api service
            routine library.  The targets defined by the Makefile in this directory
            include:

              `make'                -- compiles the API and all Models and Tests
              `make all'            -- same as `make'
              `make clean'          -- will remove appropriate .o, .mod, .a, .so and
                                       executable files
              `make install'        -- install files to `/usr/local/lib' by default
              `make uninstall'      -- delete files installed by `make install'
              `make openkim-api'    -- compiles only the API
              `make examples'       -- copies examples into the appropriate
                                       directories (no overwrite)
              `make examples-force' -- copies examples into the appropriate
                                       directories (overwrite)
              `make examples-clean' -- remove all examples from the MODEL_DRIVERS,
                                       MODELS, and TESTS directories.

5. Verify that the compilation was successful by running a Test.

          The provided example Tests read in the name of a Model (or Models)
          which they use to perform their calculations.  For most Tests the
          name of the Model can be piped in using an `echo' command.  For
          example, the following Fortran 90 Test reads in one Model:

          % cd $KD/TESTs/test_Ar_free_cluster_CLUSTER_F90
          % echo "model_Ar_P_MLJ_CLUSTER_C" | ./test_Ar_free_cluster_CLUSTER_F90

         (See the README files in the Test directories for an explanation of what
          the Tests do.)

6. Each Test (and Model) has its own make file for compiling and linking. If changes are made to the code, re-compile (from the $KD directory).

Mixing, shift, table, tail correction, restart, rRESPA info:

This pair style does not support the pair_modify mix, shift, table, and tail options.

This pair style does not write its information to binary restart files, since KIM stores the potential parameters. Thus, you need to re-specify the pair_style and pair_coeff commands in an input script that reads a restart file.

This pair style can only be used via the pair keyword of the run_style respa command. It does not support the inner, middle, outer keywords.

Restrictions:

This pair style is part of the KIM package. It is only enabled if LAMMPS was built with that package. See the Making LAMMPS section for more info.

This current version of pair_style kim is compatible with the openkim-api package version 1.2.0 and higher.

Related commands:

pair_coeff

Default: none