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Re^7: How to reduce memory constraints for DFT calculations of say 5th row above elements...?

Pavlo Solntsev

Run two jobs and see which one is thefastest. You may also check number of basis functions for each case and number of shells.

You can get this information even for smaller system: H2MoS4 or H2Mo2S5 etc.

Just do it.


On Mon Apr 28 '14 8:42am, Siddheshwar Chopra wrote
>Dear Pavlo,
>Sorry for replying late. As suggested by you,  I have now preoptimized the sample. But I don't know how much time will it take to finish DFT optimization using LanL2DZ or SBKJC. I am unable to estimate the time it would need to optimize. The sample contains 15 Mo and S atoms each with 14 H atoms.


>On Tue Apr 22 '14 8:58pm, Pavlo Solntsev wrote
>>X-ray structure? Similar compounds?
>>You may try to switch DLC off (nzvar=0) and use MINI basis to preoptimize the geometry. You may face with a problem with SCF minimization at the first step if your geometry is not good. Otherwise, you may build your molecule from scratch. It is your responsibility to build geometry in this way. You may find Z-matrix editors also very useful. There are a lot of tools available (wxmacmolplt, avogadro, chemcraft, gabedit etc.)

>>On Tue Apr 22 '14 8:18pm, Siddheshwar Chopra wrote
>>>Dear Alex,
>>>Yes I too noticed it Alex. But I got these coordinates after an initial optimization using Avogadro with conjugate gradients and Ghemical forcefield.. Infact such problems I even noticed when I use metal atoms too. Please suggest me how should I provide realistic geometry when metals or heavy atoms are used?
>>>I haven't tried FIREFLY to do this yet.


>>>On Tue Apr 22 '14 7:55pm, Alex Granovsky wrote
>>>>Dear Siddheshwar,

>>>>the input geometry is definitely wrong. Al bond orders are way
>>>>too short. This makes DLC coordinates generator crazy.
>>>>You should provide a realistic geometry.

>>>>Kind regards,
>>>>Alex Granovsky
>>>>On Tue Apr 22 '14 7:11am, Siddheshwar Chopra wrote
>>>>>Dear Alex,
>>>>>The o/p file is attached for your reference. I am getting this message:

>>>>> Fatal error : not enough memory to perform the requested task!
>>>>>   665376426   additional words of memory are required!

>>>>>I have to increase the memory, but cannot get rid of the error. My laptop has 2GB RAM...


>>>>>On Tue Apr 22 '14 0:55am, Alex Granovsky wrote

>>>>>>and what is the exact error message? It would be just fine if you
>>>>>>could provide sample input and output files.  

>>>>>>Kind regards,
>>>>>>Alex Granovsky
>>>>>>On Mon Apr 21 '14 8:40am, Siddheshwar Chopra wrote
>>>>>>>Dear Sir,
>>>>>>>I am trying to run DFT calculations for 5th row and beyond elements on my i3 processor laptop with 2GB RAM. I am using SBKJCs for the same. But I am continuously getting the memory errors. Please suggest me how to go about this situation. I am using the following commands:

>>>>>>> $SYSTEM MEMORY=194459319 aoints=dist TIMLIM=5295600 KDIAG=0 $END
>>>>>>> $STATPT opttol=10E-7 NSTEP=200 Method=GDIIS $END
>>>>>>> $SMP HTTFIX=.f. $END
>>>>>>> $p2p p2p=.t. mxbuf=2048 dlb=.t. $END
>>>>>>> $SCF dirscf=.t. fdiff= .f. diis=.t. $END  
>>>>>>> $DFT HFX(1)=0.15 LMAX=41 NRAD=99 $end
>>>>>>> $ZMAT DLC=.t. AUTO=.t. $END
>>>>>>> $SCF NCONV=7 $END


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