I think there are two common uses:
- setting a specific value of a distance, angle, dihedral as part of a scan (e.g., how does the energy change around this torsion)
- setting up the geometry of a non-bonded cluster (e.g., water dimer as indicated above)
In general, I’ve used other methods. But it came up a few times in the survey results and it seems other methods weren’t very discoverable. So I want to improve some task-based documentation as well as discoverability. (The z-matrix editor will probably also help.)
There’s probably a good way to have this in the manipulate tool (or a new tool). Several people have asked for ways to rotate a Cp ring around the axis.