libOMM

Software Technical Information

Language

Fortran 2008

Documentation Tool

Sphinx, ReStructuredText

Application Documentation

ESL wiki

Relevant Training Material

See usage examples in the examples directory of the source code.

Licence

Simplified BSD

Purpose of Module

libOMM solves the Kohn-Sham equation as a generalized eigenvalue problem for a fixed Hamiltonian. It implements the orbital minimization method (OMM), which works within a density matrix formalism. The basic strategy of the OMM is to find the set of Wannier functions (WFs) describing the occupied subspace by direct unconstrained minimization of an appropriately-constructed functional. The density matrix can then be calculated from the WFs. The solver is usually employed within an outer self-consistency (SCF) cycle. Therefore, the WFs resulting from one SCF iteration can be saved and then re-used as the initial guess for the next iteration.

Background Information

libOMM is a software library to be used within a calling code. It is built on top of the MatrixSwitch library for dealing with matrix storage and operations. Both libraries are developed within the same repository project (see Source Code), but are self-contained within separate directories.

Software Technical Information

License

Simplified BSD

Language

Fortran 2008

Documentation Tool

Source code documentation in progress.

Application Documentation

The ESL wiki

Relevant Training Material

See usage examples in the examples directory of the source code.

Installation

The source code of the LibOMM module is bundled in the git repository of the omm-bundle software which you can obtain using git:

git clone https://gitlab.e-cam2020.eu/ESL/omm.git

The source code of the LibOMM module itself is contained in a subdirectory with the same name, LibOMM.

Note

The information contained in the Installation and Testing sections are likely to work with the latest version of the source code from the repository. If this is not the case you can revert to the commit where the information is guaranteed to work:

git checkout  7eda3275

1. Enter the src directory.
2. Copy make.inc.example to make.inc and modify it to suit your needs. MSLIBPATH should point to the MatrixSwitch directory (default in make.inc.example is for the version included in the distribution). LibOMM should be compiled with the -DCONV flag. Some available options for FPPFLAGS are:
   • -DHAVE_MPI: enable MPI parallel routines
   • -DHAVE_LAPACK: enable LAPACK routines (currently necessary for preconditioning/Cholesky factorization)
   • -DHAVE_SCALAPACK: enable ScaLAPACK routines (requires -DMPI)
   • -DNORAND: fixed seed for the random number generator. Enable for testing purposes.
   • -DCBIND: use ISO_C_BINDING for LOGICAL inputs in the wrapper interfaces. Enable for linking to C.
3. Type make -f Makefile.manual.
4. Type make -f Makefile.manual install.

Note

We provide also the possibility to build modules with Autotools. You can find the related documentation in the following files:omm-bundle and LibOMM/doc

Testing

The examples directory contains a number of small programs that make use of libOMM with MatrixSwitch. These can be useful both for testing the installation and for learning how to use the library. To compile them:

1. Enter the examples directory.
2. Copy make.inc.example to make.inc and modify it to suit your needs. Be aware that make.inc in the src directory will also be used.
3. Type make -f Makefile.manual.

Each example contains a header explaining what the program does and providing sample output to compare against.

Source Code

The source code is available from the E-CAM Gitlab under the omm-bundle project. The libOMM directory can be found here.