# Example: Vibrational Circular Dichroism (VCD): NHDT¶

Download VCD_COG_NHDT.run

Analytical frequencies with subsequent calculation of vibrational circular dichroism (VCD)

The VCD keyword can be used to calculate VCD spectra. It is important to note that the VCD keyword only works in combination with the keys AnalyticalFreq and symmetry NOSYM.

Recommended is use to use high accuracy for the geometry optimization which one needs to do before the frequency calculation. This simple example is an NHDT molecule, which is NH3 where one hydrogen atom is replaced with deuterium and another with tritium.

Note that the fragment t21 names, like t21.N, are made by the adf script, and here this knowledge is used.

\$ADFBIN/adf <<eor
Atoms
N         0.000000    0.000000    0.010272
H        -0.471582   -0.816803    0.407861
H.D       0.943163    0.000000    0.407861
H.T      -0.471582    0.816803    0.407861
End

AtomProps
H.D m=2.014101778
H.T m=3.01604927
End

Basis
Type TZP
Core None
End

Symmetry NOSYM

xc
GGA BP86
end

Fragments
N     t21.N
H     t21.H
H.D   t21.D
H.T   t21.T
End

BeckeGrid
quality verygood
End

AnalyticalFreq
End

VCD
end input
eor