Dear Users,

After having some trouble with NumForce I realised it would be more accurate to add

`weight derivatives` to

`$dft` in my control file as well as run NumForce with the

`-central` tag. See page 276 of the Turbomole 7.3 manual:

4. Numforce additionally requires the file gradient and will not work, if the calculation

is not done at a stationary point of the molecular total energy. For reliable results,

always use Numforce with the option -central (i.e. central differences) and be aware

of effects due to the step length (option -d real;, default value is 0.02 a.u.). It is

strongly recommended to use Numforce in DFT calculations only with the option

weight derivatives in $dft, since this provides more accurate gradients and thus

frequencies, see Section 22.2.12

This did help my situation but I cannot find any details about how these change the calculation. Is there a paper about Turbomole explaining these options? Could someone give a brief explanation for why adding weight derivatives improves the accuracy of my gradient?

Best,

Dempsey