ADF has a fragment oriented approach: the poly-atomic system to be computed is conceptually built up from fragments, the molecular one-electron orbitals are calculated as linear combinations of fragment orbitals, and final analyzes of e.g. the bonding energy are in terms of fragment properties. The fragments may be single atoms or larger moieties.
When you compute a system in terms of its constituent fragments, these fragments must have been computed before and their properties must be passed on to the current calculation. This is done by attaching fragment files, which contain the necessary information. A fragment file is simply the standard result file of an adf calculation on that fragment.
When using Basic Atoms as fragments, you do not need to create the fragment files yourself. Instead, you may use the Basis key, and ADF will create the required fragment files automatically. We therefore recommend this feature for starting ADF users.
Basic atoms
