This repository contains a standalone implementation of a light-weight ONIOM interface.

The default CMake and meson builds compile a statically linked library (liblwoniom.a) that can be linked in other projects.

The library contains implementations for partitioning of a molecular system into the individual ONIOM fragments, including saturation of bonds with hydrogen linking atoms, and the reconstruction of respective energies, gradients and Hessian matrices.

Adhereing to the eponymous light-weight aspect, no potentials are implemented in the library itself as it is intended for the use in other codes. A standandalone command line app can be built with the -Dbuild_exe=true option, which offers a demonstration of input file formats and capabilities to test the ONIOM partition. main.f90 in app/ demonstrates the library's in-code usage.

Make sure you have the following dependencies installed:

• CMake and make, or meson and ninja build systems
• Fortran and C compilers (e.g., gfortran/gcc or ifort/icc)

Follow these steps to build the project:

1. Create a build directory and navigate to it

   mkdir _build
   cd _build

2. Export the compilers (here for example ifort/icc) and depending on your chosen build system set up the build:

   • generate the build files using CMake:

     FC=ifort CC=icc cmake ..

   • generate the build files using meson:

     FC=ifort CC=icc meson ..

   If you wish to build the an app binary, add -Dbuild_exe=true to either the cmake or meson setup command.

3. Depending on your chosen build system, build the project. If you have multiple cores/processors, you can speed up the build process by specifying the number of cores to use with the -j option. For example, to use 4 cores:

   • With CMake/make:

     make -j4

   • With meson/ninja:

     ninja -j4

To clean the build files, simply delete the build directory:

rm -rf _build