#!/bin/sh

# 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) 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.

# Five calculations are performed:
# - Scalar relativistic spin-restricted
# - Scalar relativistic open shell spin-restricted
# - Scalar relativistic spin-unrestricted
# - Spin-Orbit relativistic spin-restricted
# - Spin-Orbit relativistic spin-unrestricted collinear

# First a scalar relativistic spin-restricted calculation is performed. The
# TAPE21 of this calculation is saved as a fragment in the next spin-
# unrestricted calculation, using only 1 SCF iteration, which is a way to get
# the scalar relativistic spin-restricted open shell result for the magnetic
# dipole hyperfine interaction.


$ADFBIN/adf   <<eor
title  TiF3  scalar relativistic restricted
noprint sfo frag functions
Atoms
  Ti    0    0   0
  F   1.780   0   0
  F  -0.89  1.5415252187363007 0
  F  -0.89 -1.5415252187363007 0
End
Basis
 Type TZ2P
 Core None
End
XC
  GGA Becke Perdew
End
relativistic scalar zora
eor

mv TAPE21 t21.TiF3
rm logfile

$ADFBIN/adf   <<eor
title  TiF3  scalar relativistic open shell restricted
noprint sfo frag functions
ESR
End
qtens
Atoms
  Ti    0    0   0 f=TiF3
  F   1.780   0   0 f=TiF3
  F  -0.89  1.5415252187363007 0 f=TiF3
  F  -0.89 -1.5415252187363007 0 f=TiF3
End
Fragments
  TiF3   t21.TiF3
End
XC
  GGA Becke Perdew
End
charge 0 1
unrestricted
scf
 Iterations 0
End
relativistic scalar zora
eor

rm TAPE21 logfile


# Next a spin-unrestricted SCF calculation is performed to get the scalar
# relativistic spin-unrestricted result for the magnetic dipole hyperfine
# interaction.


$ADFBIN/adf   <<eor
title  TiF3  relativistic open shell unrestricted
noprint sfo frag functions
ESR
End
qtens
Atoms
  Ti    0    0   0 f=TiF3
  F   1.780   0   0 f=TiF3
  F  -0.89  1.5415252187363007 0 f=TiF3
  F  -0.89 -1.5415252187363007 0 f=TiF3
End
Fragments
  TiF3   t21.TiF3
End
XC
  GGA Becke Perdew
End
charge 0 1
unrestricted
relativistic scalar zora
eor

mv TAPE21 TiF3_scalar_zora.t21
rm logfile 


# Then, for the same molecule, we compute the G-tensor in a Spin-Orbit run
# (spin-restricted).

# The here-computed and printed Dipole Hyperfine interaction misses the terms
# from the spin-density at the nucleus: compare with the outcomes from the first
# calculation.

# In each of the calculations, the QTENS key invokes the computation of the
# Electric Quadrupole Hyperfine interaction.

# 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 (and also for the Q-tensor) this plays
# a minor role, but for reasons of consistency both calculations use the same
# basis set and (absence of) frozen core.


$ADFBIN/adf   <<eor
title  TiF3  relativistic spinorbit open shell restricted
noprint sfo frag functions
ESR
End
qtens
Atoms
  Ti    0    0   0 f=TiF3
  F   1.780   0   0 f=TiF3
  F  -0.89  1.5415252187363007 0 f=TiF3
  F  -0.89 -1.5415252187363007 0 f=TiF3
End
Fragments
  TiF3   t21.TiF3
End
XC
  GGA Becke Perdew
End
relativistic spinorbit zora
eor

mv TAPE21 TiF3_SO_zora.t21
rm logfile


# Finally a spin-orbit coupled spin-unrestricted calculation is performed using
# the collinear approximation. Note that symmetry NOSYM is used.


$ADFBIN/adf   <<eor
title  TiF3  relativistic spinorbit open shell unrestricted collinear
noprint sfo frag functions
ESR
End
qtens
symmetry nosym
unrestricted
collinear
Atoms
  Ti    0    0   0 f=TiF3
  F   1.780   0   0 f=TiF3
  F  -0.89  1.5415252187363007 0 f=TiF3
  F  -0.89 -1.5415252187363007 0 f=TiF3
End
Fragments
  TiF3   t21.TiF3
End
XC
  GGA Becke Perdew
End
relativistic spinorbit zora
eor

mv TAPE21 TiF3_SO_coll.t21
rm logfile