Periodic ForceField

The forcefield engine can be used to optimize the geometries of periodic systems. When specifying bonds, via the System%Bondorders key block, one should also specify the bonds that pass through a cell boundary. The GUI does this automatically. You can also simply set the key System%GuessBonds to true, and then UFF-guessed bonds will be used.

When the system contains charges, Ewald summation is used for 3D periodic systems. For 1D and 2D periodic systems the Coulomb interaction is evaluated using real-space cutoffs with an optional reaction field correction.