Restrictions and pitfalls

In the current implementation, only the electron density of the embedded system is calculated. Therefore, only properties that depend directly on the electron density (e.g., dipole moments) are available. In addition, the TDDFT extension allows the calculation of electronic excitation energies and polarizabilities, and NMR shieldings can be calculated.

EVERYTHING ELSE IS NOT YET IMPLEMENTED. THE RESULTS OBTAINED FOR OTHER PROPERTIES MIGHT BE MEANINGLESS.

In particular, interaction energies and energy gradients are not yet available.

Kinetic energy functional:
Although the effective embedding potential is derived from first principles using universal density functionals, the ADF implementation relies on approximations. Currently, two implemented approximations are recommended [188]: PW91K, which uses electron densities and the corresponding gradients to express the non-additive kinetic energy component of the embedding potential, or TF (Thomas-Fermi LDA functional), which does not use gradients at all. Either approximation is applicable only in cases where the overlap between electron densities of the corresponding interactions is small. Note: so far, no approximation has been developed for the strong-overlap case - two subsystem linked by covalent bonds for instance.