Convergence problem...

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Posts 31
Hi, I'm having trouble getting optimizing a system..
It gives the error as

dft optimize failed                                                                     0
------------------------------------------------------------------------
This type of error is most commonly associated with calculations not reaching convergence criteria

This is the inout (.nw) file I'm using ..

start ho_hocl

geometry units angstroms
O                  0.33520249    2.39077715   -0.00683931
H -0.37981087 0.74868511 0.17285391
O -0.82593007 -0.08154900 -0.00959877
Cl 0.27430978 -1.31115211 -0.00263665
H 1.29229047 2.31606903 -0.00797856
end

basis
  • library 6-311++G**
end

dft
mult 2
xc m06-2x
iterations 2000000000000
end

task dft optimize
task dft freq

Hope someone can help me with this.
Thanks a lot.
Edited On 2:10:11 PM PST - Tue, Jan 21st 2014 by Mhiranya

Forum Vet
Threads 10
Posts 1623
Mhiranya,
A way to converge this input is by first converging a HF calculation, then using the HF Molecular Orbital to start
the m06-2x calculation.
The input below implement this methods.
Cheers, Edo


start ho_hocl

geometry units angstroms
O                  0.33520249    2.39077715   -0.00683931
H                 -0.37981087    0.74868511    0.17285391
O                 -0.82593007   -0.08154900   -0.00959877
Cl                 0.27430978   -1.31115211   -0.00263665
H                  1.29229047    2.31606903   -0.00797856

end

basis
 *  library 6-311++G**
end

dft
mult 2
xc hfexch
vectors input atomic output hf.mos
end
task dft

dft
xc m06-2x
grid fine
vectors input hf.mos output m062x.mos
end

task dft


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Threads 15
Posts 31
Edo,
I tried the input you gave but still I'm getting error saying the optimization failed and calculations not reaching the convergence criteria.
Thanks

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Posts 1623
Mhiranya
Please post or upload the full output/error file.
Thanks

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Threads 15
Posts 31
here it is... hope you can help me with this.. Thanks


   3 O                |   2 H                |     1.83455  |     0.97080
4 Cl | 3 O | 3.20503 | 1.69603
5 H | 1 O | 1.84364 | 0.97561
------------------------------------------------------------------------------
number of included internuclear distances: 3
==============================================================================



==============================================================================
                                internuclear angles
------------------------------------------------------------------------------
center 1 | center 2 | center 3 | degrees
------------------------------------------------------------------------------
2 H | 3 O | 4 Cl | 102.39
------------------------------------------------------------------------------
number of included internuclear angles: 1
==============================================================================



------------------------------------------------------------------------
dft optimize failed 0
------------------------------------------------------------------------
This type of error is most commonly associated with calculations not reaching convergence criteria
------------------------------------------------------------------------
For more information see the NWChem manual at http://www.nwchem-sw.org/index.php/NWChem_Documentation


For further details see manual section:

Forum Vet
Threads 10
Posts 1623
OK, This is not the full output file, but it's probably enough.
The geometry optimization is now running out of geometry steps (from the default 20).
In other words, your run has computed 20 energy points, but the minimum has not been reached yet.
To fix this, please add the following to your input file.

driver
 maxiter 99
end

task dft optimize
task dft freq

Clicked A Few Times
Threads 15
Posts 31
It worked.
Thank you very much Edoapra.
By the way so can we change the '99' to some other number (greater than 20) ??

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Threads 15
Posts 31
one more thing, Is there a way to get partial charges of each atom ..
Thanks a lot.


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