# 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
```