Problems with negative frequencies

From NWChem

Viewed 501 times, With a total of 4 Posts
Jump to: navigation, search

Just Got Here
Threads 2
Posts 3
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 cm-1. I tried to re-optimize the geometry and using a tighter energy convergence of 5d-9 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 6-311++G**
end

dft
 xc b3lyp
mult 1
direct
grid fine
smear
convergence energy 5d-9 damp 45 ncydp 0 dampon 1d99 dampoff 1d-4
end
set tolguess 1d-3

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

Forum Vet
Threads 10
Posts 1623
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 re-run the calculation with this new geometry, all frequencies will be positive

Clicked A Few Times
Threads 2
Posts 5
Quote:Edoapra Jan 16th 11:12 pm
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;" ...
Then, if you re-run the calculation with this new geometry, all frequencies will be positive


I have a similar problem with a negative-frequency 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 re-run 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 5d-9 damp 40 ncydp 0 dampon 1d99 dampoff 1d-4 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 2
Posts 5
Following the advices in these threads
http://www.nwchem-sw.org/index.php/Special:AWCforum/st/id2535/Trouble_with_negative_freque...
http://www.nwchem-sw.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.

Forum Vet
Threads 10
Posts 1623
Quote:Sergbuto Aug 16th 3:29 am
Following the advices in these threads
http://www.nwchem-sw.org/index.php/Special:AWCforum/st/id2535/Trouble_with_negative_freque...
http://www.nwchem-sw.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.

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 1d-10 damp 40 ncydp 0 dampon 1d99 dampoff 1d-4 
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 



Forum >> NWChem's corner >> Running NWChem



Who's here now Members 0 Guests 1 Bots/Crawler 0


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