Fonames

Background
ADF uses symmetry-adapted fragment orbitals (SFOs) as its basis. These SFOs are generally orthonormal linear combinations of atomic orbitals. This makes it difficult to determine which individual atomic orbitals form the basis in calculations that have any symmetry. In addition, ADF allows "fragment" calculations which use the molecular orbitals of the fragments (FOs, or fragment orbitals) for building up the calculated molecular orbitals.

The difficulty in handling the basis for a molecule with symmetry and the availability of extra information in the fragment calculations makes using aonames (as specified for the other formats) inappropriate, except for certain circumstances. Therefore, an extra member called fonames is available for the adfparser.

Examples
C1+C4_1S+1S - Orbitals from carbon 1 and carbon 4 can interact, and their 1S orbitals mix in a positive manner

C1+C4_1Px-1Px - Orbitals from carbon 1 and carbon 4 can interact, and their 1Px orbitals mix in a negative manner

bdt1_37A - Molecular orbital 37A from the fragment bdt1

Logfile requirements
ADF: There are no required inputfile options for fonames to be suppored; however, if one wishes to have SFOs map directly to atomic basis functions, there are two requirements. First, the Symmetry NOSYM option must be given to force ADF to not linearly combine atomic orbitals into SFOs. Second, fragment calculations cannot be done (for obvious reasons). Also, it is suggested that Eigval 99999 99999 be put into an Eprint block of the input file of a spin-restricted calculation so that every molecular orbital energy will be printed.