Thanks for the response Rick!
That clued me in to the fact that I was only writing the correl function to the card but was not also telling CHARMM to write that card to a new file. It works perfect when I use the following:

enter ph1a dihed sele segid HETA .and. resid 1 .and. ( type C23 .or. type C19 .or. type C17 .or. type C15 ) end
enter ph1b dihed sele segid HETA .and. resid 1 .and. ( type C17 .or. type C15 .or. type C9 .or. type C12 ) end
traj firstu 61 skip 5000 nunit 1

open unit 22 write card name res_1_phi_1.dat
write ph1a unit 22 dumb time
* RESIDUE 1 phi1 dihedral angles

Last edited by ASmittie; 09/15/21 08:10 PM.