CO: asymptotically correct XC potentials

Sample directory adf/CO_model

For property calculations, xc potentials with asymptotically correct (-1/r) behavior outside the molecule, the results tend to be superior to regular LDA or GGA calculations. This is especially true for small molecules and for properties that depend heavily on the proper description of the outer region of the molecule. In the example, all-electron basis sets are used. This is mandatory for the SAOP potential.

$ADFBIN/adf -n1 <<EOR
create C  $ADFRESOURCES/TZ2P/C
end input
EOR
mv TAPE21 t21.C

$ADFBIN/adf -n1 <<EOR
create O  $ADFRESOURCES/TZ2P/O
end input
EOR
mv TAPE21 t21.O

In the next example, excitation energies are calculated with the GRACLB potential. This potential requires one number as argument: the experimental ionization potential in atomic units. This number can be either based on an experimental value, or on previous GGA total energy calculations.

$ADFBIN/adf <<EOR
title CO excitations grac potential
 
INTEGRATION 6.0

XC
 Model GRACLB 0.515
End

Atoms
O  0             0   0
C  1.128205364   0   0
end

Excitation
 Lowest 10
 Onlysing
End

Fragments
 O t21.O
 C t21.C
End


end input
EOR

rm TAPE21 logfile

The same calculation with the SAOP xc potential would differ in the XC block only:

XC
 Model SAOP
End

SAOP depends on the orbitals which makes it more expensive to evaluate than GRAC for large molecules.