# Example: ESR g-tensor, A-tensor, self consistent spin-orbit coupling: VO¶

```
#!/bin/sh
# The ESR parameters of VO are calculated with the collinear approximation for
# unrestricted Spin-Orbit coupled calculations. In this example the VO-molecule
# has three unpaired electrons.
# You calculate Electron Spin Resonance properties with the keywords ESR and
# QTENS. ESR is a block-type key and is used to compute the G-tensor or the
# Nuclear Magnetic Dipole Hyperfine interaction. QTENS is a simple key and
# invokes the computation of the Nuclear Electric Quadrupole Hyperfine
# interaction.
# Proper usage of the key ESR requires that you do one of the following:
# A Spin-Orbit calculation, spin-restricted, with exactly one unpaired electron,
# or (b) A Spin-Orbit calculation, spin-unrestricted in the collinear
# approximation, or (c) No Spin-Orbit terms and spin-unrestricted. In case (a)
# and (b) you obtain the G-tensor. In case (b) and (c) you get the Magnetic
# Dipole Hyperfine interaction.
# Note: in case (a) the program also prints a Magnetic Dipole Hyperfine
# interaction data, but these have then been computed without the terms from the
# spin-density at the nucleus. Note: in case (b) and (c) one can have more than
# one unpaired electron. Note: in case (b) one has to use symmetry NOSYM.
# Two calculations are performed:
# Scalar relativistic spin-unrestricted (case c)
# Spin-Orbit relativistic spin-unrestricted collinear (case b)
# We first calculate the Dipole Hyperfine interaction:
# a spin- unrestricted calculation without Spin-Orbit coupling.
# Note that one has to use ALLPOINTS in the calculation for a linear molecule to
# get results for the nuclear magnetic dipole hyperfine interaction. For an
# accurate calculation of the hyperfine interaction the numerical quality is set
# to VeryGood.
AMS_JOBNAME=scalar $AMSBIN/ams <<eor
System
atoms
V 0 0 0
O 0 0 1.589
End
End
Task SinglePoint
Engine ADF
AllPoints
ESR
End
QTens
ZFS
basis
core None
type TZ2P
End
numericalquality verygood
relativity
level scalar
formalism ZORA
end
Unrestricted
SpinPolarization 3
XC
GGA Becke Perdew
End
EndEngine
eor
# Then a spin-orbit coupled spin-unrestricted calculation is performed using the
# collinear approximation. Note that symmetry NOSYM is used.
AMS_JOBNAME=so $AMSBIN/ams <<eor
System
atoms
V 0 0 0
O 0 0 1.589
End
End
Task SinglePoint
Engine ADF
ESR
End
QTens
basis
core None
type TZ2P
End
numericalquality verygood
relativity
level spin-orbit
formalism ZORA
spinorbitmagnetization collinear
end
SCF
AccelerationMethod LISTf
End
symmetry nosym
Unrestricted
XC
GGA Becke Perdew
End
EndEngine
eor
```