# Example: LFDFT: g-tensor of Co(acacen)¶

```
#!/bin/sh
# Application of the Ligand Field DFT approach for the calculation
# of the g-tensor. The g-tensor is only calculated for Kramer doublet states.
# This example calculates the g-tensor of the ground and excited doublet states
# of Co(acacen) with a Co d^7 electron configuration.
# First an average of configuration calculation (AOC) is performed, where 7
# electrons are equally distributed over the 5 orbitals that have the most
# dominant Co 3d character. Depending on the electron configuration this might
# be a non-trivial task. Here the Keeporbitals=0 and Freeze functionality is used,
# such that ADF will on successive SCF cycles assign electrons to the MOs
# that maximally resemble - in spatial form - those that were occupied in 0th
# (in fact 1st) cycle. Note that the orbitals that have the most
# dominant Co 3d character in the 1st cycle are orbitals 71, 72, 73, 74, and 75,
# whereas at the end of the SCF they are 71, 72, 73, 74, and 77.
#
# Symmetry NOSYM should be specified.
SCM_LFDFT="$AMSHOME/examples/adf/Co_LFDFT/LFDFT"
export SCM_LFDFT
$AMSBIN/ams <<eor
System
Atoms
Co 0.000000 0.000000 0.000000
N 1.327385 1.278147 0.000000
N 1.327385 -1.278147 0.000000
O -1.395357 1.224920 0.000000
O -1.395357 -1.224920 0.000000
C 2.704031 0.764453 0.000000
C 2.704031 -0.764453 0.000000
C -1.309408 2.515386 0.000000
C -1.309408 -2.515386 0.000000
C 1.166666 2.611094 0.000000
C 1.166666 -2.611094 0.000000
C -0.103243 -3.216502 0.000000
C -0.103243 3.216502 0.000000
H 3.246281 -1.139682 0.884137
H 3.246281 1.139682 0.884137
H 3.246281 1.139682 -0.884137
H 3.246281 -1.139682 -0.884137
C -2.626185 3.259046 0.000000
C -2.626185 -3.259046 0.000000
C 2.374732 3.518898 0.000000
C 2.374732 -3.518898 0.000000
H -3.453721 -2.540862 0.000000
H -3.453721 2.540862 0.000000
H -0.145492 4.305797 0.000000
H -0.145492 -4.305797 0.000000
H 3.008094 3.350507 0.884680
H 3.008094 -3.350507 0.884680
H 3.008094 3.350507 -0.884680
H 3.008094 -3.350507 -0.884680
H -2.710536 3.904463 0.886944
H -2.710536 -3.904463 0.886944
H -2.710536 3.904463 -0.886944
H -2.710536 -3.904463 -0.886944
H 2.061821 -4.568536 0.000000
H 2.061821 4.568536 0.000000
End
Charge 0
End
task SinglePoint
Engine adf
Symmetry NOSYM
IrrepOccupations
A 140 1.4 1.4 1.4 1.4 1.4
End
Occupations Keeporbitals=0 Freeze
basis
Core None
Type DZ
PerAtomType Symbol=Co File=ZORA/TZP/Co
End
XC
GGA PBE
End
EndEngine
eor
# When the AOC calculation is ready, you need to make sure that indeed the
# partially occupied orbitals are dominantly d orbitals. In the ADF output you
# can find the character of the MOs in the list of all MOs, ordered by energy,
# with the most significant SFO gross populations.
# First the LFDFT calculation is performed without spin-orbit coupling (soc 0),
# in which pure spin states are calculated, doublets and quartets in this case.
# Next the LFDFT calculation is performed including spin-orbit coupling (soc 1),
# which is needed for the g-tensor calculation. In this case there is 1
# shell, and the nlval for 3d is '3 2'. The MO indices should be the
# fractionally occupied levels of the AOC calculation (in this case 71 72 73 74 77).
# One should be careful when interpreting the g-tensor for 2 Kramer doublets
# that are close in energy. In the effective Hamiltonian used to interpret ESR
# experiments, an effective spin=3/2 might be used.
$AMSBIN/lfdft << eor
adffile ams.results/adf.rkf
nshel 1
nlval 3 2
MOind 71 72 73 74 77
soc 0.0
DegeneracyThreshold 1.0E-5
eor
$AMSBIN/lfdft << eor
adffile ams.results/adf.rkf
nshel 1
nlval 3 2
MOind 71 72 73 74 77
soc 1.0
DegeneracyThreshold 1.0E-5
eor
```