input [configuration]


This card modifies the electron configuration. It allows the user to specify the ground-state occupation numbers of the orbitals of a species of atoms, either by atomic number Z or by potential type iph. It is possible to assign atoms with the same Z to different potential types with different configurations. The parameter input can take the following values:

  • feff7 signifying the same occupation numbers as were used in this old FEFF version;
  • file indicating there’s a file called ‘config.inp’ containing the relevant information
  • card stating that the information is passed inside the card itself in the optional parameter


Note that several instances of CONFIG card can appear in feff.inp and all will be taken into account. There is a syntax to be used for specifying configurations; it follows the usual noble gas notations closely. The resulting configuration is written to file ‘config.dat’ for user inspection. The general format is

iph name [NobleGas] istate iocc- [iocc+] istate ...

where iph is a potential index of feff.inp and name a 2-letter element name (C, Au, ...). If iph is negative, the card applies to all atoms of type name. It can even be used when there are no such atoms specified in feff.inp. (Due to the presence of a core hole or when the ION card is used, feff may use this information.) The configuration can optionally be specified from a noble gas; acceptable values are He, Ne, Ar, Kr, Xe, Hg, or Rn. All remaining fields must specify states. istate = 1s, 2p, 4f, ... For s-states, only one occupation number iocc follows; for higher states, a l-1/2 and a l+1/2 occupation number is required. Occupation numbers can be fractional (e.g. 1.5). A positive number indicates a ’valence state’; a negative number indicates a ’core state’. This distinction is only used when calculating the exchange-correlation potential and has no implications for the rest of the calculation.

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