Forum General > Miscellaneous

Really deep SCF energies DFT (with dscf)

(1/2) > >>

marilu98:
Dear all,
I'm computing ground state energies at B3LYP/6-31+G*  (defining manually the basis file) and for some of my systems the SCF (within dscf module) do not converge and gives really deep energies (of the order of -10^6 hartree).
I'm quite sure about the basis specified since it works for other "similar" systems.

I tried to modify $scforbitalshift, $scfdamp, gridsize, type of guess, but without success. I'd like to try to modify the threshold for basis linear dependencies and the threshold for neglecting one electron integral. Do you know if there are some keywords to do the latter within dscf module ?

Did any of you encounter this type of problems ?

I thank you all in advance.

Best regards
Marilu

uwe:
Hello,

my guess would be that the functional is causing those numerical errors, this can happen if the basis set generates some really unusual density and density derivatives at certain points.

Does the same input run with a predefined basis set (not a manually modified one)?

Best Regards

marilu98:
Thank you for your reply.

I don't think that is a problem of the functional (I tried also other xcf like tpssh and pbe0).
With aug-cc-pVDZ I have no problems, as well as with bs (external or built in) without diffuse functions (6-31G*, 3-21G*, cc-pVDZ,...).

The problem is that B3LYP/6-31+G* level is not working for some of my systems (namely 12 out of 48), so it is not a systematic error. My guess it's that for these systems linear dependencies are more crucial....thus, I'd like to remove some of them (if it is possible).

Thank you once again

Best regards

uwe:
Hi,

is the input structure prone to linear dependencies of the basis set if diffuse functions are used? Like a fullerene where all diffuse functions 'flood' the inner part of the fullerene?
As far as I can see aug-cc-pVDZ is not less diffuse than 6-31+G* (I just downloaded both basis sets for carbon from https://www.basissetexchange.org/ and compared them).
Is it possible to post the structure of one of those cases (coord file and also the basis set file you have used)?
Best Regards

marilu98:
Hi,
thank you very much once again. In fact, I have problems with systems that contain triple CC bonds.
Here an example (it is from the paper J. Chem. Theory Comput. 2022, 18, 2, 1046–1060):
$coord
    9.27006233815159     -4.56563200912835      0.00013379544421       h
    4.64141236904137     -4.32483962923246      0.00013182805034       h
    5.05918122897159      3.75748513925418     -0.00010634112513       h
    9.66505382813530      3.54143798936859     -0.00010887127944       h
   -3.67501791919848     -3.89309077933371     -0.00010509711842       h
   -3.25648850932071      4.19556853915043      0.00011925041120       h
   -8.32979991840199     -3.64789074931242     -0.00010594314881       h
   -7.93772671848856      4.41415218923358      0.00011623176269       h
  -15.81144469698963     -0.50727138483899     -1.67389502958465       h
  -15.75527819702021     -3.44057121940902     -0.00010840943037       h
  -15.81145089699207     -0.50737682191914      1.67386171976020       h
   16.41873589675920      2.04080322952146     -0.00006053284106       h
   13.80513209730624      3.27359241934086     -1.68893740959647       h
   13.80512039725591      3.27368692926867      1.68873124973594       h
    8.35084343836196     -2.73888994941181      0.00007836070629       c
    5.74629668879938     -2.60666967941831      0.00007860126843       c
    4.49886966908027     -0.26110449798891      0.00001062063877       c
    5.97959980891925      1.93352382967140     -0.00005539221908       c
    8.59585792826932      1.80436951956161     -0.00005627037481       c
    9.81767446813259     -0.53413285394070      0.00001026385847       c
    1.82241367963363     -0.12226715902900      0.00000922356424       c
   -0.45911807593796     -0.00608386365412      0.00000770327957       c
   -3.13570901941989      0.13323481802946      0.00000705000125       c
   -4.60739961919282     -2.07607416960626     -0.00005649241763       c
   -4.37115621920461      2.48437982950287      0.00006990720545       c
   -7.21746430856807     -1.93788686959910     -0.00005681008059       c
   -6.97894704856623      2.61135661953761      0.00006833816584       c
   -8.43051093826820      0.40687496393239      0.00000522736041       c
  -11.22667899787731      0.66458740692910      0.00000708666194       c
  -15.12622359708390     -1.48762030975725     -0.00004640146910       c
   14.37355899722264      2.24752188963408     -0.00007215975899       c
  -12.34226999752111      2.65789218946130      0.00005136653552       o
  -12.41664749751367     -1.59239539976045     -0.00004424018933       o
   13.13702549744587     -0.95154658274258      0.00001396280839       s
$end

I agree with you: 6-31+G* has less diffuse functions with respect to aug-cc-pVDZ... this is why I can't spot properly the problem.
The only difference is that aug-cc-pVDZ is implemented and I used 6-31+G* as implemented in QChem.

Best regards

Navigation

[0] Message Index

[#] Next page