# Example: open shell NMR (pNMR) shielding: O2¶

```
#!/bin/sh
# Example calculation open shell NMR (pNMR) chemical shielding.
# This can only be done at the scalar relativistic ZORA level,
# symmetry NOSYM, all electron basis sets,
# and one needs to include the key ALLINONE in the input for NMR
# Needed are the ESR g-tensor, the ESR hyperfine interaction on the nuclei,
# and the orbital dependent part of the NMR chemical shielding.
# The calculation of the orbital dependent part of the NMR chemical shielding
# should be done at the end.
# The ESR g-tensor and ESR A-tensor will be written to adf.rkf, and the nmr
# program will use those to calculate a temperature dependent contribution
# to the NMR chemical shielding.
# Effects due to zero-field splitting are neglected (possibly important for S>1/2).
# The temperature dependent part can be huge and is highly dependent on the
# calculated A-tensor (hyperfine interaction), which is highly dependent
# on the used basis set and used XC-functional, especially if the spin-polarization effects
# on the nuclei are important, like this is the case in this example for O2.
# For an accurate evaluation of the spin-polarization density at the nucleus it is
# important to use an all-electron basis set for the nuclei that one is interested in,
# avoiding the frozen core approximation.
# The basis sets in the directories ZORA/TZ2P-J, ZORA/QZ4P-J are
# recommended for accurate hyperfine calculations.
# For heavy elements the incorporation of a Gaussian finite nucleus model can be important.
# However, one should have really large basis sets with tight basis functions to observe this
# effect in calculations.
# The basis sets in the directories ZORA/TZ2P-J, ZORA/QZ4P-J are suitable for finite nucleus calculations.
# Remark: do not use restricted open shell Kohn-Sham (ROKS), since that would (incorrectly) give
# (almost) zero hyperfine interaction.
AMS_JOBNAME=SR "$AMSBIN/ams" << eor
Task SinglePoint
System
Atoms
O 0.000 0.000 -0.604
O 0.000 0.000 0.604
End
End
Engine ADF
Basis
Type TZ2P-J
Core None
End
Occupations IntegerAufbau
Unrestricted Yes
SpinPolarization 2
NumericalQuality Good
Symmetry NOSYM
XC
GGA PBE
End
SAVE TAPE10
EndEngine
eor
# Calculation of the ESR A-tensors, which are written to adf.rkf
"$AMSBIN/cpl" << eor
adffile SR.results/adf.rkf
tape10file SR.results/TAPE10
hyperfine
atoms 1 2
END
eor
rm logfile TAPE15
# Calculation of the ESR g-tensor, which is written to adf.rkf
"$AMSBIN/nmr" << eor
adffile SR.results/adf.rkf
tape10file SR.results/TAPE10
NMR
gfactors
out iso tens
u1k best
calc all
END
eor
rm logfile TAPE15
# Calculation of the orbital dependent part of the NMR chemical shielding
# The ESR g-tensor and ESR A-tensors will be read from adf.rkf, and the nmr
# program will use those to calculate a temperature dependent contribution
# to the pNMR chemical shielding.
# ALLINONE is required.
"$AMSBIN/nmr" << eor
adffile SR.results/adf.rkf
tape10file SR.results/TAPE10
ALLINONE
NMR
out iso tens
atoms 1 2
u1k best
calc all
End
eor
rm logfile TAPE15
```