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Davide Vanossi

vanossi.davide@unimore.it

Dear Alex,

thank you very much for this suggestion. Surely I’ll give a try to it.

Have a nice day.

Davide

On Thu Nov 10 '11 6:06pm, Alex Granovsky wrote

----------------------------------------------

>Dear Davide,

>For MCSCF, I'd suggest to try using either semi-converged

>UHF orbitals, orbitals of positively charged system or system

>of different multiplicity. This may need some orbital reordering

>directives. With Firefly, SOSCF usually converges well even for

>problematic systems. If it does not, try to perform several FOCAS

>steps before SOSCF. The simplest way is to use e.g.:

>

$mcscf numfo=5 $end

>This will force five FOCAS steps before launching SOSCF.

>Best wishes,

>Alex

>

>

>On Tue Nov 8 '11 11:00am, Davide Vanossi wrote

>----------------------------------------------

>>Dear Alex,

>> thank you very much for your kind reply.

>>Actually I know very well the need to perform an MCSCF description for Co isolated atom. But how can I obtain, for my cluster (Ag37Co), an acceptable (converged) initial guess for using it in the next MCSCF calculation? Using fshift=0.15-0.2 didn’t help a lot.

>>Thank you again.

>>Have a nice day

>> Davide

>>On Sun Nov 6 '11 11:41pm, Alex Granovsky wrote

>>----------------------------------------------

>>>Dear Davide,

>>>actually, Firefly' DFT code has problems converging just an isolated

>>>Co atom with e.g., mult=4. The reason is very simple. As Sanya has already

>>>mentioned, this state actually requires MCSCF for correct description.

>>>Indeed, there are both empty and occupied degenerated d orbitals so SCF oscillates

>>>between solutions having different occupation numbers for different

>>>orbitals. Increasing $scf fshift to say 0.15 or so helps. Nevertheless,

>>>one should generally realize that DFT can be inadequate and that

>>>there exist multiple (quasi)degenerated solutions of KS equations for this system.

>>>

>>>

>>>As to system with Co near Ag cluster, my guess is that as Co is far

>>>away the cluster, the convergence problems are caused by the same

>>>reason. Try to move Co atom closer to the surface.

>>>Best regards,

>>>Alex

>>>

>>>

>>>

>>>On Fri Nov 4 '11 2:04pm, Davide Vanossi wrote

>>>---------------------------------------------

>>>>Dear Amir,

>>>> I’m absolutely agree with you and, in fact, I tried the lanl2dz from the beginning; unfortunately this introduced, on my system, a quasi linear dependence on the basis set which is not a good companion “to cure” the SCF convergence problem. For the moment I have “solved” the problem using another quantum chemistry package (NWChem) which permits to obtain a feasible SCF convergence even for the singlet multiplicity case.

>>>>Thank you very much for your interest.

>>>>Have a nice day.

>>>> Davide

>>>>

>>>>

>>>>On Fri Oct 28 '11 11:56am, Amir Nasser Shamkhali wrote

>>>>------------------------------------------------------

>>>>>Dear Davide

>>>>>I think that relativistic effects can be important for Ag atom. So, it's better to perform calculations with an ECP basis set which has been included relativistic effects (spin-orbit coupling) such as LANL2DZ and etc. Also these basis sets reduces the cpu time and memory considerably. You can download them form this site:

>>>>>https://bse.pnl.gov/bse/portal

>>>>>Please note that spin-orbit coupling reduces spin multiplicity and do not use high spin cases. The 2S+1=3 or 5 or 7 is sufficient.

>>>>>Best wishes

Fri Nov 11 '11 11:55am

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