# *XAMFI¶

Options for the (extended) atomic-mean field aka **(e)amf** module for the .X2C Hamiltonian,
developed and written by S. Knecht, M. Repisky, H. J. Aa. Jensen and T. Saue, 2013-2022.
The HDF5 interface for XAMFI was developed and implemented by K. N. Spauszus (U Bonn/Germany) and S. Knecht.

Warning

The XAMFI module requires a working HDF5 installation as well as h5py in your python env!

The **(e)amf** module has been described in [Knecht2022].
Based on atomic calculation it provides two-electron scalar-relativistic **and** spin-orbit
picture-change corrections for the two-component X2C Hamiltonian (in a molecular or atomic) framework.
Since it is completely integrated in the SCF framework of DIRAC, it can explot all its capabilities for efficient
atomic calculations, for example the use of atomic supersymmetry.

For a detailed example of how to use the *XAMFI module, see the **x_amfi** test of the DIRAC test suite
or have a look at the tutorial.

The keywords below are vaild for both, atomic (mean-field) as well molecular calculations.

Warning

Do not use approximations like .LVCORR for the parent 4-component Hamiltonian. Always use .DOSSSS in the atomic molecular-mean field calculations.

## .AMF¶

Activates the atomic mean-field model for two-electron scalar-relativistic **and** spin-orbit
picture-change corrections. See also Algorithm 1 in [Knecht2022] for further information.

## .EAMF¶

Activates the **extended** atomic mean-field model for two-electron scalar-relativistic **and** spin-orbit
picture-change corrections. See also Algorithm 2 in [Knecht2022] for further information.

## .ATOMIC¶

Activates a `deprecated(!)`

simplified version of the atomic mean-field model for two-electron scalar-relativistic **and** spin-orbit
picture-change corrections. Used only for testing/debugging purposes.

Warning

Do not use this option in production calculations.

## .DEBUG¶

Activates debug output in the *XAMFI module.

Warning

**CAUTION**: This will lead to extremely verbose output