From owner-chemistry@ccl.net Sat Mar  2 16:58:00 2024
From: "Tobias Kramer Tobias.kraemer[#]mu.ie" <owner-chemistry_-_server.ccl.net>
To: CCL
Subject: CCL:G: Problem with relaxed scans in G16 Rev C.02
Message-Id: <-55105-240302165721-22600-TAu6QkwiNfH958oQJj5Qew_-_server.ccl.net>
X-Original-From: "Tobias  Kramer" <Tobias.kraemer : mu.ie>
Date: Sat, 2 Mar 2024 16:57:19 -0500


Sent to CCL by: "Tobias  Kramer" [Tobias.kraemer!^!mu.ie]
Hi all,

I've recently started to use Gaussian 16 Rev C.02 (somewhat unintended...). I've noticed that my 
relaxed scans are now terminating prematurely, ie. before the scan has done a good number of steps.
To run scan I routinely use, like many others, the addredundant option via 
opt(addredundant,maxcycles=10). I always restrict the number of optimisation steps (here 10) because I 
only need approximate energies and geometries along the scan coordinate (saves time). Previous 
versions of Gaussian (even the Rev B of G16!) would generally move to the next step defined along the 
scan coordinate when the number of steps is exceeded (that's the whole point). I have never had any 
issues with this approach, and this provided a convenient way to explore the potential energy and locate 
transition states. 

Now it seems that the in G16 C.02 the job simply exits when the number of steps is exceeded for a 
particular step and the whole calculation terminates. So I get to step 2 or so before the job stops, and 
obviously I don't have an energy profile. It makes sense that this is "normal" behaviour of Gaussian, but it 
has always worked for scans (it would be the individual optimisation at a given step that would fail, but 
Gaussian would move on to the next step rather than exit completely) Does anyone know whether there is 
a way to override this behaviour or am I missing something? 

Thanks

Best wishes,

Tobias