CCL: Converges using HF and hybrid DFT, but fails to converge using pure DFT

 Sent to CCL by: "Dr. Vitaly Chaban" [vvchaban[-]gmail.com]
 Thanks everyone for interesting suggestions. I had to finally
 recognize, that the basis set I initially tried to make use of, was
 not enough to provide a decent description of the system's
 wavefunction. So, the basis set was forcibly enlarged, and this
 removed the convergence problem. Expensive, but doable.
 Dr. Vitaly V. Chaban
 On Wed, Feb 12, 2014 at 4:40 PM, Cory Pye cpye,ap.smu.ca
 <owner-chemistry]~[ccl.net> wrote:
 >
 > Sent to CCL by: Cory Pye [cpye**ap.smu.ca]
 > Hello,
 >
 > Another thing to try is turning off the incremental Fock matrix
 construction.
 >
 > SCF=(XQC,NoIncrFock)
 >
 > It appears that it is restarting the incremental Fock matrix construction
 > several times before not converging.
 >
 > Also make sure that the accuracy of your grid matches the accuracy of your
 SCF.
 >
 > -Cory
 >
 > On Tue, 11 Feb 2014, Dr. Vitaly Chaban vvchaban::gmail.com wrote:
 >
 >>
 >> Sent to CCL by: "Dr. Vitaly Chaban" [vvchaban/./gmail.com]
 >> On Tue, Feb 11, 2014 at 6:57 PM, Sebastian Kozuch
 >> seb.kozuch!A!gmail.com <owner-chemistry()ccl.net> wrote:
 >> >
 >> > Sent to CCL by: Sebastian Kozuch [seb.kozuch(a)gmail.com]
 >> > That happens sometimes. Pure GGA have some extra convergence
 difficulties.
 >> > You may try to take the converged orbitals in the checkpoint file
 from a
 >> > hybrid DFT and use them as a guess for the GGA, and try with
 scf(qc) or
 >> > scf(xqc). More expensive, but life is always more expensive than
 our
 >> > expectations.
 >>
 >>
 >> The bad thing is that even SCF=QC with Guess=Read does not work
 >> adequately. Below follows the logfile after a couple of hours of
 >> iterations. The guess came from "B3LYP/CEP-31G*
 SCF=Conver=9", and the
 >> failed convergence example used "BLYP/CEP-31G*"
 >>
 >> Unless there is no other magic way, I will have to decrease the SCF
 >> criterion down to what BLYP can afford. Maybe indeed a bit exotic
 >> system...
 >>
 > <stuff deleted>
 >>  >>>>>>>>>> Convergence criterion not
 met.
 >>  SCF Done:  E(RB-LYP) =  -477.317424055     A.U. after   65 cycles
 >>             NFock= 64  Conv=0.47D-05     -V/T= 2.4474
 >>
 > <stuff deleted>
 >
 >    *************    !  Dr. Cory C. Pye
 >  *****************  !  Associate Professor
 > ***   **    **  **  !  Theoretical and Computational Chemistry
 > **   *  ****        !  Department of Chemistry, Saint Mary's University
 > **      *  *        !  923 Robie Street, Halifax, NS B3H 3C3
 > **      *  *        !  cpye(a)crux.stmarys.ca   http://apwww.stmarys.ca/~cpye
 > ***     *  *    **  !  Ph: (902)-420-5654  FAX:(902)-496-8104
 >  *****************  !
 >    *************    !  Les Hartree-Focks (Apologies to Montreal Canadien
 Fans)>
 >