From NWChem
Viewed 1081 times, With a total of 4 Posts

Just Got Here
Threads 2
Posts 3


9:19:41 AM PST  Thu, Dec 20th 2018 

Dear NWchem community,
I ran a DFT calculation on a small molecule in solvation model using nwchem 6.8. It was converged but it has a negative frequency of about 162 cm1. I tried to reoptimize the geometry and using a tighter energy convergence of 5d9 but still no success.
Here is the input file:
geometry units angstroms autosym 0.2
C 0.30975950 1.32138254 0.00000000
C 0.04718087 0.20210007 0.00000000
H 0.13238927 1.79961154 0.88134209
H 1.39114031 1.48379999 0.00000000
H 0.13238927 1.79961154 0.88134209
O 1.27722401 0.45562499 0.00000000
O 0.92245943 0.99906777 0.00000000
end
basis
* library 6311++G**
end
dft
xc b3lyp
mult 1
direct
grid fine
smear
convergence energy 5d9 damp 45 ncydp 0 dampon 1d99 dampoff 1d4
end
set tolguess 1d3
driver
tight
clear
maxiter 200
end
cosmo
dielec 8.51
end
task dft optimize
task dft freq numerical
Any suggestions will greatly appreciated.
Regards,
Sophia

Edited On 5:28:39 AM PST  Thu, Dec 27th 2018 by Sophia.sagala




Edoapra Forum:Admin, Forum:Mod, bureaucrat, sysop


Forum Vet
Threads 12
Posts 1675


4:12:36 PM PST  Wed, Jan 16th 2019 

Sophia
If you look at the frequencies output, you will find the section " Negative Nuclear Hessian Mode 1 "
If you use as new geometry the one as listed under
" Geometry after 100.0% step for mode 1;"
C 0.09310508 1.34795637 0.00258095
C 0.00214260 0.18798365 0.00404920
H 0.67531313 1.77100773 0.72045709
H 1.12474372 1.70215805 0.27599438
H 0.16807654 1.71637592 1.03984743
O 1.16957720 0.66899511 0.02412262
O 1.06729404 0.85799128 0.02636247
Then, if you rerun the calculation with this new geometry, all frequencies will be positive




Clicked A Few Times
Threads 3
Posts 6


9:48:32 AM PDT  Wed, Aug 14th 2019 

Quote:Edoapra Jan 16th 11:12 pmSophia
If you look at the frequencies output, you will find the section " Negative Nuclear Hessian Mode 1 "
If you use as new geometry the one as listed under
" Geometry after 100.0% step for mode 1;" ...
Then, if you rerun the calculation with this new geometry, all frequencies will be positive
I have a similar problem with a negativefrequency mode (even the frequency value is similar 167.765 [cm**1]) despite the tighter energy convergence and optimisation used. I have tried to follow this advice to put new geometry from " Geometry after 100.0% step for mode 1;" in the input file and rerun the calculation but it did not help. It converged to a bit lower energy but the mode is still at the negative frequency.
My input file:
start PCO
echo
scratch_dir .
permanent_dir .
memory 6000 mb
charge 5
geometry units angstroms
O 2.63694460 3.94597618 0.00000016
C 2.90591488 2.64073309 0.00000013
O 1.89749032 1.74606799 0.00000006
O 4.16999971 2.21992605 0.00000016
O 0.01986707 0.00426229 1.90601275
Pu 0.02688600 0.00141010 0.00000009
O 0.01986716 0.00426243 1.90601265
O 4.00241237 2.53107489 0.00000018
O 0.53932580 2.50059322 0.00000008
C 3.73858336 1.22669983 0.00000014
C 0.81223868 3.82105873 0.00000012
O 4.73281162 0.34093790 0.00000017
O 2.45996385 0.79869299 0.00000004
O 0.18408865 4.70381661 0.00000013
O 2.07680464 4.23684930 0.00000013
end
BASIS
Pu library "Stuttgart_RLC_ECP"
C library "Stuttgart_RLC_ECP"
O library "Stuttgart_RLC_ECP"
END
ECP
Pu library "Stuttgart_RLC_ECP"
C library "Stuttgart_RLC_ECP"
O library "Stuttgart_RLC_ECP"
END
dft
xc b3lyp
noio
direct
vectors input PCO_01.movecs output PCO.movecs
iterations 5000
convergence energy 5d9 damp 40 ncydp 0 dampon 1d99 dampoff 1d4 rabuck 20 levlon 0.2
smear
grid fine
odft
mult 4
end
driver
tight
MAXITER 600
end
set int:txs:limxmem 25621940
set driver:linopt 0
task dft optimize
task dft freq

Edited On 12:37:15 AM PDT  Thu, Aug 15th 2019 by Sergbuto




Clicked A Few Times
Threads 3
Posts 6


4:29:56 AM PDT  Fri, Aug 16th 2019 

Following the advices in these threads
http://www.nwchemsw.org/index.php/Special:AWCforum/st/id2535/Trouble_with_negative_freque...
http://www.nwchemsw.org/index.php/Special:AWCforum/st/id2763/Frequency_Analysis_Grid_Dens...
I also used "grid huge" but it did not help either. Furthermore, the use of this option increased the calculation time to the extent that the numerical frequency calculation is faster with the "grid fine" option. The latter calculation gives only positive frequencies.
There seems to be a problem with analytical frequency calculations in NWChem.




Edoapra Forum:Admin, Forum:Mod, bureaucrat, sysop


Forum Vet
Threads 12
Posts 1675


3:07:26 PM PDT  Mon, Aug 19th 2019 

Please try the following input. The major change is the line set dft:no_prune t. This is required for the correct integration of the contribution to XC potential from the Pu atom.
The associated output does not contain any negative frequency.
The input change increases the time to solution. We are working at a better fix that does not increase the time to solution.
start pco_new
echo
memory 6000 mb noverify
charge 5
geometry units angstroms
O 4.72777782 0.00036022 0.00000000
C 3.80305541 0.95770261 0.00000000
O 2.49547411 0.62952538 0.00000000
O 4.16561764 2.23897376 0.00000000
O 0.00000000 0.00000000 1.91098610
Pu 0.00000000 0.00000000 0.00000000
O 0.00000000 0.00000000 1.91098610
O 0.14380067 4.72701758 0.00000000
O 1.79292203 1.84638129 0.00000000
C 1.07213291 3.77239390 0.00000000
C 2.73092249 2.81469129 0.00000000
O 2.36420087 4.09419559 0.00000000
O 0.70255209 2.47590666 0.00000000
O 4.02181697 2.48804382 0.00000000
O 2.36357695 4.09455580 0.00000000
end
BASIS spherical
Pu library "Stuttgart_RLC_ECP"
C library "Stuttgart_RLC_ECP"
O library "Stuttgart_RLC_ECP"
END
ECP
Pu library "Stuttgart_RLC_ECP"
C library "Stuttgart_RLC_ECP"
O library "Stuttgart_RLC_ECP"
END
dft
xc b3lyp
direct
vectors input atomic output PCO_new.movecs
iterations 5000
convergence energy 1d10 damp 40 ncydp 0 dampon 1d99 dampoff 1d4
grid fine
smear
odft
mult 4
end
driver
xyz
tight
end
set int:txs:limxmem 25621940
set quickguess t
set dft:no_prune t
task dft optimize
task dft freq



AWC's:
2.5.10 MediaWiki  Stand Alone Forum Extension
Forum theme style by: AWC