#! /bin/sh

$ADFBIN/adf << eor
title NH3 frequencies in symmetric displacements

atoms
   N               0.0000    0.0000    0.0000
   H               0.4729    0.8190    0.3821
   H              -0.9457    0.0000    0.3821
   H               0.4729   -0.8190    0.3821
end

Basis
 Type TZP
 Core Small
End

geometry
  frequencies Symm
end

thermo  T=300,400

BeckeGrid
 quality good
End

end input
eor

mv TAPE21 NH3_symm.t21

$ADFBIN/adf << eor
title NH3 frequencies

define
  rNH=1.02
  theta=112
  phi=120
end

atoms   Z-matrix
  XX   0 0 0
  N    1 0 0   1.0
  H    2 1 0   rNH   theta
  H    2 1 3   rNH   theta   phi
  H    2 1 4   rNH   theta   phi
end

Fragments
 N t21.N
 H t21.H
End

geometry
  optim  cartesian
  frequencies
end

thermo  T=300,400

BeckeGrid
 quality good
End

end input
eor

# Rename the TAPE21 so we can restart with other masses

mv TAPE21 restart.t21


#  Calculate a different isotope of H. It will differ from the 
#  original one only in the mass of the nucleus.

$ADFBIN/adf << eor
create H M=2.014101779 $ADFRESOURCES/TZP/H
eor

mv TAPE21 t21.D

# Repeat the frequency calculation with different fragments. 
# It is important to preserve symmetry at this step so
# we replace fragment files for ALL H atoms.
# If you want to replace only one fragment then
# the original calculation must be performed the same way, with
# different fragment names

$ADFBIN/adf << eor
title NH3 frequencies

define
  rNH=1.02
  theta=112
  phi=120
end

atoms   Z-matrix
  XX   0 0 0
  N    1 0 0   1.0
  H    2 1 0   rNH   theta          
  H    2 1 3   rNH   theta   phi    
  H    2 1 4   rNH   theta   phi    
end

Fragments
  N t21.N
! The different isotope mass sits in the next line.
  H t21.D
End

geometry
  optim  cartesian
  frequencies
end

! Restart the frequency calculation. 
! In fact ADF should perform only one geometry cycle
restart restart.t21

thermo  T=300,400

BeckeGrid
 quality good
End

end input
eor

mv TAPE21 NH3.t21