## Firefly and PC GAMESS-related discussion club

Learn how to ask questions correctly

** Re^7: density convergence **
Alex Granovsky

gran@classic.chem.msu.su

Dear Siddheshwar,this will slightly increase computation time. Numeric DFT integration

is fast with Firefly so the performance penalty will not be dramatic.

Note, use of default grid is enough in most cases and most convergence

problems are *not* caused by the grid settings. The suggestion to use

tighter grid was only one of the possible ways to explore.

Kind regards,

Alex Granovsky

On Mon Jan 20 '14 10:27am, Siddheshwar Chopra wrote

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

>Dear Alex,

>Will adding "$dft lmax=47 nrad=127 $end" to the input file INCREASE the computation time? If yes then by how much? I am facing the convergence problem too, but am worried about the computation time. Please help. Earlier I had used nrad=99.

>

>

>On Wed Jan 1 '14 7:46pm, Alex Granovsky wrote

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

>>Dear David,

>>As to DFT grids, try to set

>>

$dft lmax=47 nrad=127 $end

>>Kind regards,

>>Alex Granovsky

>>

>>

>>

>>On Wed Jan 1 '14 4:23pm, David G. wrote

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

>>>>Dear Pavel

>>>yes actually I am using diffuse functions and I should have dropped off some of them to reach equilibrium. After then I should use diffuse functions to compute the properties of the system accurately. Could I increase the DFT grid accuracy using just LAMX ?

>>>

>>>

>>>Dear Slawomir

>>>adding the following line didn't help to make density convergence better than before.

>>>$CONTRL INTTYP=HONDO ICUT=15 ITOL=35 LEXCUT=5 $END

>>>

>>>

>>>Many Thanks for your kind attentions and comments.

>>>Sincerely David

>>>

>>>

>>>

>>>On Wed Jan 1 '14 9:50am, Pavlo Solntsev wrote

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

>>>>Dear David.

>>>>My two cents.

>>>>Do you use diffuse functions? Is geometry really good? In the first case you may drop off some diffuse functions to achieve a convergence. If geometry is not good, you may try to use smaller basis set and then expend it up to desired size. Keep in mind, for DFT you may also need to increase grid accuracy, especially for transition metals.

>>>>Pavel.

>>>

Wed Jan 22 '14 1:51pm

This message read **643** times