CDFT convergence issue


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Dear all,

I am doing CDFT calculation on Ethylene Carbonate (EC) and Li-ion system. I am using following script for assigning partial negative charges to oxygen atom in EC and integer positive charge on Li keeping overall system charge as nutral. I put lithium atom far away from the EC molecule.


echo
title "EC optimization"
charge 0.0
geometry units angstroms noautoz noautosym
O 19.30226 20.00000 19.04308
C 19.31126 20.00000 20.44608
O 20.60126 20.00000 20.99608
C 21.58126 20.00000 19.83208
C 20.74826 20.00000 18.56608
O 18.32326 20.00000 21.10408
H 22.07926 21.03631 19.85908
H 22.33326 19.32131 19.90808
H 20.95926 20.71231 17.85008
H 20.92526 18.99231 18.08708
Li 12.32326 20.00000 28.10408
end
basis
  • library 6-31++G*
end

driver
maxiter 200
xyz final
end

dft
iterations 500
xc b3lyp
convergence nolevelshifting
odft
mult 2
cdft 1 1 charge -0.7
cdft 11 11 charge +1.0
end

In a set of simulations on above configuration, when I put atom charge (-0.1 to -0.5) on atom 1, it converges, but any charge lower than -0.5 (I tried -0.6 to -1.0), the simulation ended up with following error message.

CDFT failed to optimize the multipliers.
multipliers:
1 -0.1122200661
2 831.0016664469
------------------------------------------------------------------------
CDFT failed to optimize multipliers, cdft_maxiter= 50
------------------------------------------------------------------------

I also tried adding "set dft:cdft_maxiter 999" statement, but it didn't work. I run these simulations in both NWChem 6.1 and 6.3 version.

I would highly appreciate if anyone help me to figure out what is going wrong.

Thank you in advance.

Mahbub