From NWChem
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1:27:30 PM PDT  Thu, Apr 16th 2015 

Dear All,
I am benchmarking different options for running some DFT claculations and having access to large memory machines my intention is t run some fully incore calculations. For the example benchmark I am using (a C60) molecule, no matter the basis set, converges nicely in a few iterations in direct mode but when run incore fails miserably to reach convergence. I attach the two input files below. Is it possible that the starting guess is somehow different for the two? Any insight will be grately appreciated.
I am running branch 6.5 revision 26243
Cheers,
Cristián
INCORE
title "C60"
memory 2000 mw
 print low
echo
start C60
geometry "system" units angstroms nocenter noautoz noautosym noprint
load format xyz "C60.xyz"
end
set geometry "system"
basis "ao basis"
* library 321G
end
basis "cd basis"
* library "DGauss A1 DFT Coulomb Fitting"
end
dft
xc xpbe96 cpbe96
semidirect memsize 1500000000 filesize 0
end
task dft energy
DIRECT
title "rubish"
memory 2000 mw
 print low
echo
start C60
geometry "system" units angstroms nocenter noautoz noautosym noprint
load format xyz "C60.xyz"
end
set geometry "system"
basis "ao basis"
* library 321G
end
basis "cd basis"
* library "DGauss A1 DFT Coulomb Fitting"
end
dft
print low "convergence"
xc xpbe96 cpbe96
direct
end
task dft energy




Edoapra Forum:Admin, Forum:Mod, bureaucrat, sysop


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2:12:16 PM PDT  Thu, Apr 16th 2015 

Cristián
Please remove the line
semidirect memsize 1500000000 filesize 0
from your first input file, since
1) it has no effect on the SCF when CD basis set is used
2) it's used only when the starting guess is generated and, as you can see,
it has the adverse effect of generating a poorer guess than the default one.
My suggestion is not to play with the semidirect options, since  as you can see  can have unpredictable effects on the calculation accuracy

Edited On 2:12:35 PM PDT  Thu, Apr 16th 2015 by Edoapra



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