#! /bin/sh

# Spin-orbit coupled relativistic ZORA, X2C, and RA-X2C
# are compared in this example for the calculation of 
# Core Electron Binding Energies (CEBEs).
# In this case the CEBE of the 1s of Iodine in the molecule HI.
# For such calculations X2C or RA-X2C is recommended.
# Note, for more accurate calculations one should increase the basis set.
# In this example the LDA functional is used.

# Results of this example will show that for X2C the CEBE is around 33.211 keV
# and for RA-X2C the CEBE is around 33.202 keV.
# If one increases the basis set (especially in the core region), for example, with a QZ4P basis set,
# the results obtained with X2C and RA-X2C will be much closer.

# In case of ZORA, without the scaled ZORA energy correction
# the CEBE in this case is around 34.515 keV, much larger than the results with X2C or RA-X2C.
# If one includes the scaled ZORA energy correction (can be found in the output)
# the CEBE in case of ZORA is around 33.238 keV.

# NOTE: The scaled ZORA energy correction should only be used to compare two calculations
# in which the only difference in the calculation is the electron configuration.
# Then the difference in energy of this term should be added to the difference in energy of
# the two electron configurations.
# This term should not be used otherwise.
# In practice it is useful only for core excitation energy calculations.

for f in "ZORA" "X2C" "RA-X2C"
do

AMS_JOBNAME=HI_$f $AMSBIN/ams <<eor
System
  atoms
     H 0.0 0.0 0.000
     I 0.0 0.0 1.609 
  end
end

Task SinglePoint

Engine ADF
  basis
    core None
    type DZ
  end
  numericalquality good
  relativity
    level spin-orbit
    formalism $f
  end
  nuclearmodel gaussian
EndEngine
eor

AMS_JOBNAME=HI_core_$f $AMSBIN/ams <<eor
System
  atoms
     H 0.0 0.0 0.000
     I 0.0 0.0 1.609 
  end
  charge 1
end

Task SinglePoint

Engine ADF
  basis
    core None
    type DZ
  end
  numericalquality good
  relativity
    level spin-orbit
    formalism $f
    SpinOrbitMagnetization NonCollinear
  end
  unrestricted
  symmetry nosym
  irrepoccupations
    A1/2 1 0 52
  end
  nuclearmodel gaussian
EndEngine
eor
done