Matrix elements for geometric and orbital Hessians, TDDFT, etc #139
Description
The discussion in psi4/psi4#3236 reminded me about an old feature request: matrix elements for geometric and orbital Hessians, TDDFT etc. These matrix elements become quite hairy for meta-GGAs with 7 input parameters, since you get 28 derivative terms of the xc functional, each of which is coupled by some complicated expression involving derivatives of the AO basis functions.
Opening a ticket to keep this in mind.