If I have the Hessian matrix and the mass-weighted Hessian matrix for a system, I can find the normal modes from the mass-weighted Hessian and the force constants from the Hessian.
I have a list of the eigenvalues and eigenvectors, but I'm trying to figure out how to map each force constant to each vibrational mode. How would I go about doing that?
I have two sets of eigenvalue/eigenvector pairs. The eigenpairs for the mass-weighted Hessian gives me the vibrational frequencies and the eigenvectors for those frequencies. The eigenpairs for the non-mass-weighted Hessian (so, just a normal Hessian) give the force constants and the associated eigenvectors. What I want is to match the eigenpairs from the Hessian to the eigenpairs for the mass-weighted Hessian so then I'd have the force constant for each vibrational mode.
Right now I have a list of force constants and vibrational modes, but I have no way to know which force constant goes to which vibrational mode (since I don't know the reduced mass for the vibrational modes). If I can figure out how to relate the eigenvectors between the Hessian and mass-weighted Hessian, then I'd be able to pair the vibrational frequencies and force constants.