Depict an ab initio Walsh diagram with respect to the specified geometrical parameter for an assigned molecule using the Hartree-Fock 6-31G** level of theory. Include only the valence orbitals: you may omit core orbitals. One molecule will be assigned per individual.
To prepare the Walsh diagram, first you will need to optimize the geometry at the given (6-31G** HF) level of theory. Then, you will need to perform single-point energies at a series of geometries (10 increments are suggested) displaced from the equilibrium geometry. Bond lengths should be fixed at their equilibrium values; only the given parameter (usually an angle) should be allowed to change from its equilibrium value. At each geometry, perform the 6-31G** HF single-point computation and tabulate the orbital energies of all the valence orbitals (both occupied and unoccupied). If in doubt, tabulate more orbitals than you need, and cut them out later. This will keep you from having to re-run anything. You might be able to cut and paste the relevant orbital energies into a file to avoid having to write them all down. For at least one geometry point, you will need to record the orbital energies for all occupied orbitals, along with the total Hartree-Fock energy, to answer one of the questions in the discussion.
Orbitals should be labeled with their appropriate symmetry designations (e.g., 5a1) in the diagram; refer to the Q-Chem output or the Walsh diagrams in Herzberg. Note that for some molecules the Q-Chem program may choose a different axis convention than Herzberg, making some irrep labels swap. For example, for a C2v molecule, what Q-Chem calls the 1b1 orbital might be called 1b2 in Herzberg, depending on whether the molecule lies in the xz or yzplane. In such cases, Herzberg's choice is usually more acceptable.
Questions for Discussion: