# Parametrizer Documentation

## Single Molecule Parametrization

The Parametrizer module is the first step in the predictive multiscale OLED workflow. Starting with an initial guess of a single molecule 3D structure provided by the user, the Parametrizer module optimizes molecular geometry using one of our DFTEngines. For a single point calculation on the optimized geometry, partial charges are computed using an electrostatic potential fit (ESP-fit, available in the Psi4 and Turbomole Engine), the Mullikan-approach (available in all Engines) or the improved DFTB charge model CM3 (available in the DFTB Engine). These partial charges are later applied to compute the intermolecular electrostatic interaction in classical simulations (e.g. Deposit).

### Product specifications

- Input:
- Initial guess of molecular geometry (mol2-file)

- Output:
- Optimized molecular geometry (pdb file)
- Force-field files for Deposit containing Lennard-Jones parameters, partial charges and information on flexible side-groups (dihedrals) for the DihedralParametrizer

- Requirements
- IntelMPI 18.3 or larger

### Performance

The Parametrizer for geometry optimization and computation of partial charges runs a few minutes to hours (depending on the quality of the initial guess for the atom positions and the DFTEngine) on a single core. Speed up, especially for larger molecules, can be achieved using parallelization up to a single node.

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