Rigid PES Scan for ground and excited states

Questions
#1

Dear Q-Chem Community,

I am interested in a feature similar to “$scan $end” for a variable that is defined in either the z-matrix or rectangular coordinates block. Is there a way to use this feature in the current version of Q-Chem?
Although I am aware that I can run multiple inputs, but it is less convenient.
Thank you.

#2

How is what you are requesting different from JOBTYPE = SCAN? If you had, e.g.,

$scan
tors 1 2 3 4 -180 180 15
$end

that’s a torsional coordinate that might appear in a Z-matrix. Is it that you don’t want the rest of the system to be relaxed at each point? If so, your best bet is to write a script that generates a sequence of input files in Z-matrix coordinates.

#3

That is a great feature of Q-Chem. However, I need to change the values of the stretching and bending coordinates at the moment. It would be more convenient if they were gathered in a table, but I can work with multiple inputs. Thanks

#4

Do you know that you can define variables in the Z-matrix? e.g., for H2O:

$molecule
0 1
O
H 1 r1
H 1 r2 2 b

r1 0.95
r2 0.95
b  104.5
$end

so a script could just replace the numerical values of r1, r2, b (and similarly torsion angles)