Example: Numerical Frequencies: NH3¶

#! /bin/sh

# Summary:
# - Frequencies with symmetric displacements
# - Frequencies with Cartesian displacements
# - Isotope effects in the frequencies

# == Frequencies with symmetric displacements ==

# Computation of frequencies by symmetric displacements. The assumed equilibrium
# input structure should be given in Cartesian coordinates.

# The symmetry is determined automatically by the program as C(3v), from the
# input coordinates. During the calculation first symmetric atomic displacements
# are constructed. The number of such displacements in each irreducible
# representation corresponds to the number of frequencies with the corresponding
# symmetry. All displaced geometries within one representation have the same
# symmetry, which enables us to use it to speed up the computation
# significantly. 

AMS_JOBNAME=NH3_symm $AMSBIN/ams <<eor
System
  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
  Symmetrize Yes
end

Task SinglePoint

Properties
  NormalModes Yes
End

NormalModes
  Displacements Symmetric
End

Thermo
  Temperatures 300:400:10
End

Engine ADF
  title NH3 frequencies in symmetric displacements
  BeckeGrid 
    quality good
  End
  Basis 
    type TZP 
    core Small
  End
EndEngine
eor


# == Frequencies with Cartesian displacements ==

# Computation of frequencies by Cartesian displacements. The assumed equilibrium
# input structure is given in internal coordinates. 

AMS_JOBNAME=NH3_cartesian $AMSBIN/ams <<eor
System
  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
  Symmetrize Yes
end

Task SinglePoint

Properties
  NormalModes Yes
End

NormalModes
  Hessian Numerical
  Displacements Cartesian
End

Thermo
  Temperatures 300:400:10
End

Engine ADF
  title NH3 frequencies
  BeckeGrid 
    quality good
  End
  Basis 
    type TZP 
    core Small
  End
EndEngine
eor


# The symmetry is determined automatically by the program as C(3v), from the
# input coordinates. In a Frequencies calculation the symmetry (specified on
# input or computed internally) is used for analysis and in some cases to speed
# up the calculation.

# The equilibrium coordinate values are supplied as identifiers that are
# associated with values in the define block.

# The key thermo addresses the thermodynamical analysis (only available in a
# Frequencies calculation, otherwise ignored). The specification Temperatures 300:400:10
# means that the thermodynamic properties are printed for the temperature range
# 300-400K using 10 equidistant steps and for a pressure of 1.0 atmosphere
# (default).

# Frequencies calculations suffer easily from numerical inaccuracies. Therefore,
# the default numerical integration precision in a Frequencies calculation is
# higher than in an ordinary single-point or minimization run.


# == Isotope effects in the frequencies ==

# Calculate a different isotope of H, in this case deuterium.

AMS_JOBNAME=Isotope $AMSBIN/ams <<eor
System
  atoms
     N   0.0000    0.0000    0.0000
     H   0.4729    0.8190    0.3821 mass=2.014
     H  -0.9457    0.0000    0.3821 mass=2.014
     H   0.4729   -0.8190    0.3821 mass=2.014
  end
  Symmetrize Yes
end

Task SinglePoint

Properties
  NormalModes Yes
End

NormalModes
  Hessian Numerical
  Displacements Cartesian
End

Thermo
  Temperatures 300:400:10
End

Engine ADF
  title NH3 frequencies
  BeckeGrid 
    quality good
  End
  Basis 
    type TZP 
    core Small
  End
EndEngine
eor