From owner-chemistry@ccl.net Fri Oct 26 06:59:00 2018
From: "Tobias Kraemer tobias.kraemer[a]mu.ie" <owner-chemistry:-:server.ccl.net>
To: CCL
Subject: CCL:G: Low-progression Franck-Condon transitions
Message-Id: <-53529-181026065741-31274-ZGzAr9KFCM6A7pw5+4lSQQ:-:server.ccl.net>
X-Original-From: "Tobias  Kraemer" <tobias.kraemer(~)mu.ie>
Date: Fri, 26 Oct 2018 06:57:38 -0400


Sent to CCL by: "Tobias  Kraemer" [tobias.kraemer_._mu.ie]
Hello everyone,

I am interested in calculating vibrationally-resolved spectra in G16. The 
molecule in question is a phthalocyanine (pc) complex. I've followed the 
protocol detailed in the whitepaper by Barone et al., however in the 
final step (generating the spectrum) an error occurs:


     ==================================================
              Calculations of Band Intensities
     ==================================================

 -- To: vibronic fundamental state --
    Spectrum progression:    0.06%

 -- To: single overtones --
    Spectrum progression:    0.71%

 -- To: combinations of  2 simultaneously excited modes --
    Spectrum progression:    4.14%

 ERROR: Low progression after class 2. Total convergence =  4.1%.
        The vibronic spectrum will likely be unreliable. Stopping.

The whitepaper provides some possible causes, but I'd like to ask for 
some expert opinions here on CCL nonetheless. In the excited state 
optimisation I have included 6 states, of which the gradients for the 
first one are to be followed [TD=(Read,NStates=6,Root=1)].
There are a good number of keywords listed on the Gaussian16 webpage that 
relate to this type of calculation, and I'd appreciate some guidance on 
the above issue and possible ways around it. 

Thanks for your help, as always much appreciated.

Kind regards,

Tobias