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Date: Sun, 24 Oct 2004 01:12:29 -0400 (EDT)
From: Yinghua.Shen@dartmouth.edu (Yinghua Shen)
Subject: DFT single point calculation convergence problem
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Dear users,
      I ran into a DFT single point calculation convergence problem, here is the input file:
*******************************************************************************************
scf
thresh 1.0e-9
maxiter 300
end

dft
mult 1;
grid fine;
xc vwn_1_rpa 0.19 lyp 0.81 HFexch 0.20  slater 0.80 becke88 nonlocal 0.72
convergence energy 1e-9
iterations 1000
end

task dft energy

************************************************************************************************

As you see, I used iterations=1000 and grid fine, yet I still got the warning message from the output file:

*************************************************************************************************
 WARNING: error on integrated density =  0.46E-01
 greater than required accuracy of  0.10E-06
  Singularity in Pulay matrix. Error and Fock matrices removed.
 d= 0,ls=0.5,diis    89   -216.5766147656 -1.23E-08  2.79E-10  1.97E-15    49.3
 WARNING: error on integrated density =  0.46E-01
 greater than required accuracy of  0.10E-06
  Singularity in Pulay matrix. Error and Fock matrices removed.
  Singularity in Pulay matrix. Error and Fock matrices removed.
 d= 0,ls=0.5,diis    90   -216.5766147708 -5.21E-09  6.55E-10  1.29E-15    49.8
 WARNING: error on integrated density =  0.46E-01
 greater than required accuracy of  0.10E-06
 d= 0,ls=0.5,diis    91   -216.5766147660  4.78E-09  1.25E-10  3.21E-15    50.3
 WARNING: error on integrated density =  0.46E-01
 greater than required accuracy of  0.10E-06
  Singularity in Pulay matrix. Error and Fock matrices removed.
 d= 0,ls=0.5,diis    92   -216.5766147653  6.87E-10  2.88E-10  9.06E-16    50.8
 WARNING: error on integrated density =  0.46E-01
 greater than required accuracy of  0.10E-06


         Total DFT energy =   -216.576614769999
      One electron energy =   -450.219742993843
           Coulomb energy =    217.859325168436
    Exchange-Corr. energy =    -20.777534148207
 Nuclear repulsion energy =     36.561337203616

 Numeric. integr. density =     24.800564181437

****************************************************************************
DFT converged to some strange numbers, for the correct energy should be around: -218.181581622 Hartree. (calculated by gaussian 98). I don't know what I should do to get NWchem converge to this value. Any suggestions?

Thanks in advance,
Yinghua