# Example: ESR g-tensor, A-tensor, perturbative spin-orbit coupling: HgF¶

```
#!/bin/sh
# This example calculates the ESR g-tensor and A-tensor for HgF. In this example
# first spin-orbit coupling is taken into account perturbatively.
# Note that an all-electron calculation is carried out. This is relevant for the
# computation of the A-tensor, the nuclear magnetic dipole hyperfine
# interaction, where an accurate value of the spin-polarization density at the
# nucleus is important. For the g-tensor this plays a minor role. However, for
# the g-tensor calculation that includes spin-orbit coupling perturbatively, all
# electron basis sets are necessary.
# In the first example the module nmr calculates the g-tensor (subkey GFACTORS)
# using spin-orbit coupling and the external magnetic field as perturbation.
AMS_JOBNAME=HgF $AMSBIN/ams <<eor
System
atoms
Hg 0.0 0.0 0.0
F 0.0 0.0 2.804
end
end
Task SinglePoint
Engine ADF
beckegrid
quality verygood
end
basis
core None
type TZ2P
end
relativity
level scalar
formalism ZORA
end
save TAPE21 TAPE10
scf
converge 1e-7 1e-7
iterations 500
end
spinpolarization 1
symmetry NoSym
unrestricted
usespcode
xc
gga PBE
end
EndEngine
eor
$AMSBIN/nmr <<eor
tape10file HgF.results/TAPE10
adffile HgF.results/adf.rkf
nmr
gfactors
u1k best
out iso tens
end
eor
# In the second example the module cpl calculates the A-tensor (key HYPERFINE)
# using spin-orbit coupling and the nuclear magnetic field as perturbation. Note
# that one needs to set the SCF convergence criterion to a small value. For an
# accurate calculation of the A-tensor one needs a very large basis set in the
# core region (especially tight s-functions), especially for heavy nuclei. If
# one has such a large basis set in the core region, one can also see an effect
# of using a finite size of the nucleus instead of a point nucleus. Such large
# basis sets can be found for some elements in $AMSRESOURCES/ADF/ZORA/jcpl, which
# are basis sets especially designed for ESR A-tensor and NMR spin-spin coupling
# calculations.
AMS_JOBNAME=HgF_jcpl $AMSBIN/ams <<eor
System
atoms
Hg 0.0 0.0 0.0
F 0.0 0.0 2.804
end
end
Task SinglePoint
Engine ADF
beckegrid
quality verygood
end
basis
PerAtomType Symbol=Hg File=ZORA/jcpl/Hg
PerAtomType Symbol=F File=ZORA/jcpl/F
end
nuclearmodel Gaussian
relativity
level scalar
formalism ZORA
end
scf
converge 1e-7 1e-7
iterations 500
end
spinpolarization 1
symmetry NoSym
unrestricted
usespcode
xc
gga PBE
end
EndEngine
eor
$AMSBIN/cpl <<eor
adffile HgF_jcpl.results/adf.rkf
gga
hyperfine
atoms 1 2 :: calculates A-tensor for atom 1 and 2, input order
SCF Converge=1e-7
end
eor
```