# Example: Mössbauer spectroscopy: Ferrocene¶

```
#! /bin/sh
# By default in ADF the electron density at the nuclei is calculated, no input
# key is required. The electron density at the nuclei could be used for the
# interpretation of isomer shifts in Mossbauer spectroscopy. The absolute
# electron density at a nucleus heavily depends on the accuracy of the basis set
# in the core region of this nucleus, especially if relativistic effects are
# included. Important is to use the same basis set, same exchange correlation
# functional, same numerical accuracy, if electron densities at nuclei in
# different molecules are compared. For the calculation of Mossbauer quadrupole
# splittings the key QTENS is required For 57 Fe quadrupole splittings will be
# written in units of mm/s, used in Mossbauer spectroscopy Example shows a
# calculation on ferrocene with anon-relativistic, and two with a scalar
# relativistic ZORA Hamiltonian using a different all electron basis set.
# First a non-relativistic calculation.
AMS_JOBNAME=NR $AMSBIN/ams <<eor
System
symmetrize Yes
atoms
Fe 0.000000 0.000000 0.000000
C 1.215650 0.000000 1.600813
C 0.375656 -1.156152 1.600813
C -0.983481 -0.714541 1.600813
C -0.983481 0.714541 1.600813
C 0.375656 1.156152 1.600813
C 1.215650 0.000000 -1.600813
C 0.375656 1.156152 -1.600813
C -0.983481 0.714541 -1.600813
C -0.983481 -0.714541 -1.600813
C 0.375656 -1.156152 -1.600813
H 2.310827 0.000000 1.629796
H 0.714085 -2.197727 1.629796
H -1.869498 -1.358270 1.629796
H -1.869498 1.358270 1.629796
H 0.714085 2.197727 1.629796
H 2.310827 0.000000 -1.629796
H 0.714085 2.197727 -1.629796
H -1.869498 1.358270 -1.629796
H -1.869498 -1.358270 -1.629796
H 0.714085 -2.197727 -1.629796
end
end
Task SinglePoint
Engine ADF
title ferrocene
exactdensity
basis
core none
type TZP
end
numericalquality Good
qtens
xc
gga blyp
end
Relativity
Level None
End
EndEngine
eor
# Next the scalar relativistic ZORA calculations. ADF will also calculate the
# quadrupole splittings including the small component density, also called SR
# ZORA-4.
AMS_JOBNAME=SR $AMSBIN/ams <<eor
System
symmetrize
atoms
FE 0.000000 0.000000 0.000000
C 1.215650 0.000000 1.600813
C 0.375656 -1.156152 1.600813
C -0.983481 -0.714541 1.600813
C -0.983481 0.714541 1.600813
C 0.375656 1.156152 1.600813
C 1.215650 0.000000 -1.600813
C 0.375656 1.156152 -1.600813
C -0.983481 0.714541 -1.600813
C -0.983481 -0.714541 -1.600813
C 0.375656 -1.156152 -1.600813
H 2.310827 0.000000 1.629796
H 0.714085 -2.197727 1.629796
H -1.869498 -1.358270 1.629796
H -1.869498 1.358270 1.629796
H 0.714085 2.197727 1.629796
H 2.310827 0.000000 -1.629796
H 0.714085 2.197727 -1.629796
H -1.869498 1.358270 -1.629796
H -1.869498 -1.358270 -1.629796
H 0.714085 -2.197727 -1.629796
end
end
Task SinglePoint
Engine ADF
title ferrocene
exactdensity
basis
core none
type TZP
end
numericalquality Good
qtens
relativity
level scalar
formalism ZORA
end
xc
gga blyp
end
EndEngine
eor
# Next a scalar relativistic calculation is performed with a much larger basis
# set (QZ4P) in the core region. Changing the basis set will have a large effect
# on the electron density at the nucleus and a noticeable effect on the
# calculated quadrupole splittings.
AMS_JOBNAME=SR_QZ4P $AMSBIN/ams <<eor
System
symmetrize
atoms
FE 0.000000 0.000000 0.000000
C 1.215650 0.000000 1.600813
C 0.375656 -1.156152 1.600813
C -0.983481 -0.714541 1.600813
C -0.983481 0.714541 1.600813
C 0.375656 1.156152 1.600813
C 1.215650 0.000000 -1.600813
C 0.375656 1.156152 -1.600813
C -0.983481 0.714541 -1.600813
C -0.983481 -0.714541 -1.600813
C 0.375656 -1.156152 -1.600813
H 2.310827 0.000000 1.629796
H 0.714085 -2.197727 1.629796
H -1.869498 -1.358270 1.629796
H -1.869498 1.358270 1.629796
H 0.714085 2.197727 1.629796
H 2.310827 0.000000 -1.629796
H 0.714085 2.197727 -1.629796
H -1.869498 1.358270 -1.629796
H -1.869498 -1.358270 -1.629796
H 0.714085 -2.197727 -1.629796
end
end
Task SinglePoint
Engine ADF
title ferrocene
exactdensity
basis
core none
type QZ4P
end
numericalquality Good
qtens
relativity
level scalar
formalism ZORA
end
xc
gga blyp
end
EndEngine
eor
```