Customized Dihedral Forcefields

To enable efficient simulation of conformational changes of molecules during the deposition process, rotations around single bonds are applied in Deposit – so called dihedral moves. The change in energy connected to such a dihedral move is computed using dihedral forcefields. These forcefields then determine the flexibility of the molecules during deposition. As the molecular packing and therefore the electronic structure in thin films are highly sensitive to the flexibility of the deposited molecules, an accurate, molecule-specific description of the energy profile of the dihedral rotations is essential.

The DihedralParametrizer (DHP) therefore automatically computes dihedral forcefields for organic compounds using quantum-chemistry. The principle works as follows:

For each dihedralangle:

  1. Rotate the the side group step-wise around the single-bond
  2. For each step:
    • Keep the angle fixed and relax the rest of the molecule, to avoid clashes
    • Compute the energy for this configuration using one of our DFTEngines
    • Correct the energy by internal forcefield values later applied in Deposit

For molecules with multiple dihedralangles, this protocoll is modified to account for correlation effects in conformational changes.

Further details on the DHP method are provided at our DHP documentation page.