In addition to bond energies it is now possible to compute total energies with ADF by including the keyword TOTALENERGY in the input. This work is in progress.
TOTALENERGY
The total energy will be computed for the chosen XC functional (LDA, GGA, hybrid functionals, or Hartree-Fock). MetaGGA functionals, (ZORA) scalar relativistic and relativistic spin-orbit calculations, electric fields and QM/MM are not supported yet.
The total energies have not been tested extensively and should therefore be used with caution. In particular the requirements to the integration accuracy are somewhat higher than for bond energies. Tests have shown that one can expect an accuracy of roughly accint-2 decimal places in the total energies, where accint is the general integration accuracy parameter (see keyword INTEGRATION). The accuracy may be a bit higher if the investigated compound contains only first and second row atoms and a bit lower if the investigated compound also contains heavier elements. Reaction energies or relative energies obtained as difference of total energies in general benefit from error cancellation and a higher accuracy than for absolute total energies should be achieved. It is recommended to use an integration accuracy setting of 6, but at least 5. If in doubt, a convergence test with respect to the integration accuracy is recommended.
ADF normally does not calculate total energies. It calculates difference energies with respect to fragment energies. By default, these are the spherical spin-restricted atoms. For this reason total energies from other programs could not be compared to ADF directly. With the key TOTALENERGY this is now possible. Note, however, that only energy difference comparisons are meaningful. These are the only energies that play a role in chemistry of course, and for this one does not need total energies.
