How to input Hessian about geometric HOT 4 OPEN

You only need to convert it to a square matrix format. I am 99% sure that the Hessian output from Gaussian is in atomic units (Hartree/bohr^2), and that is also what geomeTRIC uses.

from geometric.

Thank you！

from geometric.

Thank you！

Hello, did you eventually figure out how to do this? I'm trying to do the same thing, trying to get the hessian from a gaussian freq calculation
I can't actually find the triangular matrix in gaussian's output either

from geometric.

I currently don't have a Gaussian frequency calculation handy to provide a detailed response. However, if a Gaussian frequency calculation does not print the Hessian (aka force constant matrix) in the output, then it will be in the .chk file which you can convert to a human-readable format with formchk. Then it is just a matter of extracting the matrix into a separate file.

from geometric.