Example: Asymptotically correct XC potentials: CO¶

#!/bin/sh

# 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.

# In the first 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
 
BeckeGrid
 Quality good
End

XC
 Model GRACLB 0.515
End

Atoms
O  0             0   0
C  1.128205364   0   0
end

Excitations
 Lowest 10
 Onlysing
End

Basis
 Type TZ2P
 Core None
End

EOR

rm TAPE21 logfile


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


$ADFBIN/adf <<EOR
title CO excitations SAOP 
 
BeckeGrid
 Quality good
End

XC
 Model SAOP
End

Atoms
O  0             0   0
C  1.128205364   0   0
end

Excitations
 Lowest 10
 Onlysing
End

Basis
 Type TZ2P
 Core None
End

EOR

mv TAPE21 CO.t21


# SAOP depends on the orbitals which makes it more expensive to evaluate than
# GRAC for large molecules, but is much easier to use, since it does not require
# an ionization potential parameter as input.