# Example: Analytic Frequencies: CN¶

Download CN_SecDeriv.run

Calculation of analytical second derivatives is requested by specifying

AnalyticalFreq
End


A good quality is specified for the numerical Becke integration to be sure of reliable results. In general, it seems advisable to use high accuracy for heavy nuclei at the moment, whereas default integration accuracy is usually sufficient for light atoms. The precision of the fit may be improved with the ZlmFit block keyword.

\$ADFBIN/adf << eor
title CN

atoms
N  -1.3  0.0   0.0
C   0.0  0.0   0.0
end

Basis
Type DZ
Core None
End

charge -1

XC
LDA Xonly
End

BeckeGrid
quality good
End

AnalyticalFreq
End

End input
eor


After SCF is completed, the energy second derivatives matrix is calculated and analysed, which yields in this case one frequency.