CCSD iterations does not converge
Clicked A Few Times
2:18:37 PM PDT - Thu, May 2nd 2013
Dear NWChem Developers:

I am trying to do a CCSD(T) optimization on HBr+ using aug-cc-pv5z on H and pp-aug-cc-pv5z on Br. The problem I am having is CCSD iteration does not converge even at 500 steps. The differences in the energy between SCF iteration is actually increasing instead of decreasing. The related output is below,

CCSD iterations

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

Iter          Residuum       Correlation     Cpu    Wall    V2*C2

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

   1   0.3947204386567  -0.5986246846772    39.4    39.9    14.9

   2   0.0777144398021  -0.5668211536264    39.3    39.8    15.0

   3   0.1507226170554  -0.5778189847214    39.4    39.9    14.9

   4   0.2654166565068  -0.5768900976901    39.5    40.0    15.0

   5   0.9146529333630  -0.5776076230098    39.4    40.0    15.1

MICROCYCLE DIIS UPDATE:                     5                     5

   6   0.0442335406897  -0.5726599439331    39.5    40.0    15.0

   7   0.0728365126228  -0.5769226318288    39.4    39.9    15.0

   8   0.2686042645653  -0.5771582128763    39.4    39.9    15.0

   9   0.6598562875828  -0.5774425649866    39.4    39.9    15.0

  10   2.8417269601096  -0.5775023587506    39.5    40.0    15.0

MICROCYCLE DIIS UPDATE:                    10                     5

  11   0.0206737603309  -0.5764805831965    39.4    39.9    15.0

  12   0.0367361772656  -0.5769149561010    39.3    39.8    15.0

  13   0.0858697482857  -0.5773548026063    39.4    39.9    15.0

  14   0.2587281370144  -0.5774284785070    39.4    39.9    15.0

 ... ...

 ... ...

 ... ...

The input file for this calculation is,


start name

echo

charge 1



memory stack 4600 mb heap 4100 mb global 14500 mb



geometry noautosym

 H              -0.17832631     0.97840869    -0.98242772

 Br              0.00496505    -0.04724133    -0.02735323

end



BASIS

H  library aug-cc-pv5z

Br library aug-cc-pv5z-pp

END



ECP

Br nelec 10

Br ul

2      1.0000000              0.0000000

Br S

2     70.0242570             49.9628340

2     31.1784120            370.0142050

2      7.1565930             10.2414390

Br P

2     46.7734710             99.1122440

2     46.1841200            198.2530460

2     21.7138580             28.2617400

2     20.9417920             56.6233660

Br D

2     50.6988390            -18.6058530

2     50.6447640            -27.9232800

2     15.4475090             -0.3796930

2     15.5002590             -0.7805830

2      2.8003910              0.0359680

2      1.0774800              0.0943970

Br F

2     14.4656060             -1.0912690

2     21.2340650             -2.8876910

END



SCF

 DOUBLET

END



tce

 FREEZE atomic

 thresh 1e-6

 maxiter 500

 scf

 ccsd(t)

end



task tce optimize

I also tried the same calculation with smaller basis (aug-cc-pvqz) and it works fine. Is this a problem related to bad wave functions due to different basis set?

Thanks in advance and best regards,

SR

Clicked A Few Times
11:04:31 AM PDT - Thu, May 9th 2013
Any one can provide any idea related to the unconvergence will be greatly appreciated.

Thanks

SR

Forum Vet
8:59:34 AM PDT - Fri, May 10th 2013
This is most likely an issue with not having the levelshift kick in. I've seen this before with large basis sets. You can try "lshift 0.2", but you should double check in the output (look for DIIS level shift) to see if it actually gets set. In some older versions we have had some issues with it not being set properly. If it doesn't get set, you may try to compile the latest development version, or next week the new release.

Bert

Clicked A Few Times
11:00:16 PM PDT - Mon, May 13th 2013
Dear Bert,

     Thank you for your reply. I have tried the options you suggested but the problem still exist. I am using NWChem 6.1.1 (which should be the latest one). Here is the information for the DIIS lshift,



         Correlation Information

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

         Calculation type : Coupled-cluster singles & doubles w/ perturbation

  Perturbative correction : (T)

           Max iterations :      500

       Residual threshold : 0.10D-05

    T(0) DIIS level shift : 0.20D+00

    L(0) DIIS level shift : 0.00D+00

    T(1) DIIS level shift : 0.00D+00

    L(1) DIIS level shift : 0.00D+00

    T(R) DIIS level shift : 0.00D+00

    T(I) DIIS level shift : 0.00D+00

  CC-T/L Amplitude update :  5-th order DIIS

               I/O scheme : Global Array Library

       L-threshold : 0.10D-05

       EOM-threshold : 0.10D-05

no EOMCCSD initial starts read in

TCE RESTART OPTIONS

READ_INT:   F

WRITE_INT:  F

READ_TA:    F

WRITE_TA:   F

READ_XA:    F

WRITE_XA:   F

READ_IN3:   F

WRITE_IN3:  F



     Does it mean the lshift has been set correctly? If so, is there more options that I can try other than wait for the new release?



     Thank you for your help.

SR

Gets Around
12:12:10 AM PDT - Fri, Jun 7th 2013
"T(0) DIIS level shift : 0.20D+00" indicates you set the level shift for the CCSD amplitude solver properly.

I find that CCSD does not always converge with diffuse basis sets. This is due to unfortunate realities of numerical linear algebra. I wish I could give you a better answer than this.

Clicked A Few Times
12:16:06 PM PDT - Fri, Jul 5th 2013
Quote:Jhammond Jun 7th 12:12 am
"T(0) DIIS level shift : 0.20D+00" indicates you set the level shift for the CCSD amplitude solver properly.

I find that CCSD does not always converge with diffuse basis sets. This is due to unfortunate realities of numerical linear algebra. I wish I could give you a better answer than this.



Another thing I noticed is, at each DIIS step, the energy decreases a little bit (very small, maybe 10-9 Hartree). So will it make sense if I make the maxiter in SCF really large and use DIIS to decrease the residuum?

Thank you very much

SR

Gets Around
12:19:49 PM PDT - Fri, Jul 5th 2013
(T) is non-iterative so the notion of convergence does not make sense.

I do not understand your reference to SCF maxiter here. Are you trying to converge the SCF or the CCSD iterations?

Clicked A Few Times
12:31:14 PM PDT - Fri, Jul 5th 2013
Quote:Jhammond Jul 5th 12:19 pm
(T) is non-iterative so the notion of convergence does not make sense.

I do not understand your reference to SCF maxiter here. Are you trying to converge the SCF or the CCSD iterations?


Sorry for the confusion. I could not get the CCSD iterations converged. and the iteration shows:
CCSD iterations

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

Iter          Residuum       Correlation     Cpu    Wall    V2*C2

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

   1   0.2812658734394  -0.8785464064858    18.1    18.2     3.6

   2   0.0584455131307  -0.8571460720421    18.1    18.3     3.6

   3   0.0209806546166  -0.8753694879529    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                     3                     3

   4   0.0166793076886  -0.8734726702560    18.2    18.3     3.6

   5   0.0083406835212  -0.8746841048019    18.1    18.2     3.6

   6   0.0059823765765  -0.8753932654371    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                     6                     3

   7   0.0038436749801  -0.8753658591552    18.2    18.3     3.6

   8   0.0023507946302  -0.8754945849824    18.2    18.3     3.6

   9   0.0026921558151  -0.8755120058603    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                     9                     3

  10   0.0007721100098  -0.8755301279887    18.1    18.2     3.6

  11   0.0004624364451  -0.8755675802626    18.1    18.3     3.6

  12   0.0003001233903  -0.8756056447170    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                    12                     3

  13   0.0002219979231  -0.8756046827711    18.1    18.2     3.6

  14   0.0001616913834  -0.8756076242349    18.1    18.3     3.6

  15   0.0001907546745  -0.8756081246472    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                    15                     3

  16   0.0000524149708  -0.8756088035823    18.1    18.2     3.6

  17   0.0000324385020  -0.8756111110847    18.2    18.4     3.6

  18   0.0000217372284  -0.8756130071232    18.2    18.3     3.6

MICROCYCLE DIIS UPDATE:                    18                     3

  19   0.0000181808334  -0.8756137082857    18.1    18.3     3.6

  20   0.0000161295062  -0.8756130007051    18.1    18.3     3.6

  21   0.0000180666516  -0.8756130492805    18.2    18.3     3.6

MICROCYCLE DIIS UPDATE:                    21                     3

  22   0.0000102414047  -0.8756127871295    18.1    18.2     3.6

  23   0.0000094218153  -0.8756131898605    18.1    18.3     3.6

  24   0.0000091600093  -0.8756132274086    18.1    18.2     3.6

MICROCYCLE DIIS UPDATE:                    24                     3

  25   0.0000090653553  -0.8756133875916    18.0    18.2     3.6

  26   0.0000089921356  -0.8756132080443    18.2    18.3     3.6

  27   0.0000089970307  -0.8756132302744    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                    27                     3

  28   0.0000088270014  -0.8756130798797    18.1    18.2     3.6

  29   0.0000087531072  -0.8756132543603    18.0    18.2     3.5

  30   0.0000087151982  -0.8756132315666    18.1    18.3     3.6



....... many steps .........



MICROCYCLE DIIS UPDATE:                   489                     3

 490   0.0000047553429  -0.8756132433250    18.3    18.4     3.6

 491   0.0000047422879  -0.8756132433638    18.1    18.2     3.6

 492   0.0000047414338  -0.8756132434023    18.1    18.2     3.6

MICROCYCLE DIIS UPDATE:                   492                     3

 493   0.0000047551186  -0.8756132433254    18.1    18.3     3.6

 494   0.0000047415363  -0.8756132433643    18.0    18.2     3.6

 495   0.0000047327345  -0.8756132434027    18.0    18.2     3.6

MICROCYCLE DIIS UPDATE:                   495                     3

 496   0.0000047547753  -0.8756132433264    18.1    18.3     3.6

 497   0.0000047417231  -0.8756132433652    18.1    18.3     3.6

 498   0.0000047409030  -0.8756132434037    18.1    18.3     3.6

MICROCYCLE DIIS UPDATE:                   498                     3

 499   0.0000047545510  -0.8756132433268    18.2    18.3     3.6

 500   0.0000047409687  -0.8756132433657    18.0    18.2     3.6

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

ccsd_energy_loc: maxiter exceeded      501

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

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

As you can see, the converge tendency is okay but it just moves really slow. In your last reply, were you trying to say increase maxiter won't help in this case? (I have tried lshift as Bert suggested and it did not work either).

Thanks again

SR

Gets Around
12:49:55 PM PDT - Fri, Jul 5th 2013
Please post your input file and I'll try to figure it out. This may be a pathological case though.

Do you think that 5e-6 is to sloppy of convergence for this problem btw?

Clicked A Few Times
12:59:44 PM PDT - Fri, Jul 5th 2013
Quote:Jhammond Jul 5th 12:49 pm
Please post your input file and I'll try to figure it out. This may be a pathological case though.

Do you think that 5e-6 is to sloppy of convergence for this problem btw?


Sorry that was a wrong click, my internet browser is really stupid...
Please delete the previous post and I will paste my input in a better way..

Thanks

SR

Clicked A Few Times
1:08:40 PM PDT - Fri, Jul 5th 2013
Quote:Jhammond Jul 5th 12:49 pm
Please post your input file and I'll try to figure it out. This may be a pathological case though.

Do you think that 5e-6 is to sloppy of convergence for this problem btw?


Thank you for your reply, please see below for my input deck,

start name

charge 1

memory stack 3600 mb heap 600 mb global 7800 mb

geometry noautosym

O                0.60987066     3.21010816     0.00000498

C               -0.06992897     2.29911529     0.00000003

O               -0.83251927     1.35696645    -0.00000100

H               -0.43462609     0.30974447     0.00001390

Br               0.08216442    -1.44068130    -0.00000054

end

BASIS

...

end

ECP

...

end

SCF

DOUBLET

END

tce

FREEZE atomic

thresh 4e-6

maxiter 1000

diis 3

scf

ccsd(t)

end

task tce optimize

I did not include basis set and ecp in my input because it is very long. The basis I used is cc-pvtz for O, C and H and pp-cc-pvtz for Br.

I don't think 5e-6 is bad for this case (i have set it to be 4-e6 to match some other cases) but I am just wondering if there is some ways to make the converge a bit more efficient or changing the convergence criteria is the only way.

Thank you very much for your kind help

SR

Forum Vet
9:08:36 AM PDT - Wed, Jul 10th 2013
CCSD convergence level
So, your correlation energy is converged to at least 7 digits. I don't think you need that many for CBS fitting. Just as a reference, convergence to 0.0001 Hartree is less than 0.1 kcal/mol. Your convergence gives you a convergence error of at most 0.0001 kcal/mol. Hence, don't think you need that high a level of convergence.

Bert


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