CCL: GAMESS Convergence Problem

 Sent to CCL by: "Brad  Rose" [brose{}live.com]
 Dear Sara,
 SCF convergence will be a problem with all the diffuse functions. It
 takes time and practice to learn how to tell what could be the cause,
 something worth your time if you plan on doing this work. The first thing
 I would consider is the integral cutoff values, these are ICUT and one
 other parameter that I don't recall offhand, I believe there should be a
 warning in your output about the integral cutoffs if you are running into
 linear dependancies (you likely are with all the diffuse functions
 present). To get a reasonable geometry close to the local minima I would
 suggest removing the diffuse functions from all but the anion and add
 dispersion correction (the dispersion correction is computationally
 cheap).
 Regards,
 Brad Rose
 Sent to CCL by: "Sara  Mahmoud" [smahmoud%x%sci.cu.edu.eg]
 Sent to CCL by Sara[smahmoud|*|sci.cu.edu.eg]
 Dear all,
 I'm trying to study the adsorption of some ions on graphene flakes using
 GAMESS-US program. When I optimize the ion-graphene system I get this
 error message after several points of optimization.
 ***** FAILURE TO LOCATE STATIONARY POINT, SCF HAS NOT CONVERGED
      UPDATED HESSIAN, GEOMETRY, AND VECTORS WILL BE PUNCHED FOR RESTART
  **** THE GEOMETRY SEARCH IS NOT CONVERGED! ****
 I am using the DFT functional B3LYP with 6-31+G(d) basis set as a
 starting level of calculation, I'm going to justify both the functional
 and basis set and then include the suitable dispersion corrections in
 single point energy calculations. This is some of the input I used:
 $CONTRL MAXIT=200 ISPHER=0
 $SCF DIRSCF=.T. SOSCF=.F. DIIS=.T. SHIFT=.T. DAMP=.t.
 $STATPT OPTTOL=0.00045 NSTEP=300
 I'm a new student in the field and have no experience in GAMESS-US
 program. What I need to know is how can I get my jobs converged? and what
 are the keywords that should I use to improve the SCF convergence for
 this kind of interaction (ion-pi-system interaction)?
 Any help concerning this point will be highly appreciated.
 Thanks in advance for all of you.
 Sara