From NWChem
Viewed 1786 times, With a total of 5 Posts

Clicked A Few Times
Threads 2
Posts 5


7:46:42 AM PDT  Tue, Jul 8th 2014 

Hello All
Can anyone please tell how to do frequency calculation in rodft level? Is analytical hessian is avaliable with rofdt?
Thank You
Sujitha




Gets Around
Threads 18
Posts 133


1:00:32 PM PDT  Tue, Jul 8th 2014 

I don't know if any of the DFT methods have analytical frequencies. Here's an example of a rodft calculation.
Title "no2geovib"
Start no2geovib
echo
charge 0
geometry units angstroms print xyz
O 0.75760 0.04378 0.06825
N 2.09353 0.04378 0.06825
O 3.42945 0.04378 0.06825
symmetry c1
end
basis "ao basis" cartesian print
* library "631G*"
end
dft
mult 2
rodft
XC m06
mulliken
end
driver
default
end
task dft optimize
task dft freq




Huub Forum:Admin, Forum:Mod, NWChemDeveloper, bureaucrat, sysop


Forum Regular
Threads 1
Posts 185


9:15:50 AM PDT  Wed, Jul 9th 2014 

Hi,
NWChem supports analytical DFT frequencies for closed shell and unrestricted open shell calculations. There are some additional limitations due to the requirement for 2nd order partial derivatives of the functional you are using. At the moment we don't have these for all functionals but I hope to have that problem fixed soon.
For RODFT the story is a bit different as there is an additional constraint (additional relative to unrestricted open shell) that the alpha and beta orbitals should be the same. This leads to an additional Lagrangian in the gradient expression with has been coded in NWChem. But we haven't worked out what this additional term means for the frequency calculations. So, you are right that if you do an RODFT frequency calculation then the 2nd derivative will be constructed by numerically differentiating the gradient.
Huub




Clicked A Few Times
Threads 2
Posts 5


11:58:45 AM PDT  Wed, Jul 9th 2014 

Thank you for the responses.
The RODFT requires with "CGMIN" . But the frequency calculatios were not possible with this option. My attempts to perform frequency calculation by removing this keyword was also unsuccessful. The options I tried for getting frequencies were as follows. As I mentioned both of these options were unsuccessful.
Thank You.
Sujitha
OPTION 1
dft
xc b3lyp
rodft
cgmin
mult 1
decomp
tolerances tight
grid xfine nodisk
end
task dft optimize
task dft freq numerical
OPTION 2
dft
xc b3lyp
rodft
cgmin
mult 1
decomp
tolerances tight
grid xfine nodisk
end
task dft optimize
dft
nocgmin
end
task dft freq numerical




Gets Around
Threads 18
Posts 133


6:44:08 PM PDT  Wed, Jul 9th 2014 

bug with DFT grid nodisk

Interesting, there seems to be a bug in using geometry optimization with DFT grid 'nodisk' option under these circumstances. This input runs quickly and terminates normally:
Title "no2geovib"
Start no2geovib
echo
charge 0
geometry units angstroms print xyz
O 0.75760 0.04378 0.06825
N 2.09353 0.04378 0.06825
O 3.42945 0.04378 0.06825
symmetry c1
end
basis "ao basis" cartesian print
* library "631G*"
end
dft
mult 2
xc b3lyp
rodft
cgmin
decomp
tolerances tight
grid xfine
end
task dft optimize
task dft freq numerical
This input produces progressively higher energy geometries until it runs out of optimization steps:
Title "no2geovib"
Start no2geovib
echo
charge 0
geometry units angstroms print xyz
O 0.75760 0.04378 0.06825
N 2.09353 0.04378 0.06825
O 3.42945 0.04378 0.06825
symmetry c1
end
basis "ao basis" cartesian print
* library "631G*"
end
dft
mult 2
xc b3lyp
rodft
cgmin
decomp
tolerances tight
grid xfine nodisk
end
task dft optimize
task dft freq numerical
@ Step Energy Delta E Gmax Grms Xrms Xmax Walltime
@        
@ 0 204.97333967 0.0D+00 0.22447 0.10581 0.00000 0.00000 4.4
@ 1 204.95545153 1.8D02 0.18350 0.08650 0.02951 0.06260 8.8
@ 2 204.94675962 8.7D03 0.16714 0.07879 0.01340 0.02843 12.8
@ 3 204.94250996 4.2D03 0.15979 0.07532 0.00640 0.01357 16.7
@ 4 204.93999303 2.5D03 0.15562 0.07336 0.00375 0.00795 19.4
@ 5 204.93749968 2.5D03 0.15160 0.07147 0.00369 0.00782 22.2
@ 6 204.93503032 2.5D03 0.14774 0.06965 0.00363 0.00769 25.1
@ 7 204.93258045 2.4D03 0.14402 0.06789 0.00358 0.00758 28.7
@ 8 204.93005490 2.5D03 0.14027 0.06613 0.00381 0.00778 33.6
@ 9 204.92697342 3.1D03 0.13582 0.06403 0.00492 0.00949 61.0
@ 10 204.92422775 2.7D03 0.13195 0.06222 0.00435 0.00844 66.9
@ 11 204.92145431 2.8D03 0.12812 0.06043 0.00439 0.00854 82.9
@ 12 204.91882836 2.6D03 0.12458 0.05877 0.00417 0.00808 89.2
@ 13 204.91620944 2.6D03 0.12112 0.05716 0.00417 0.00807 96.7
@ 14 204.91367270 2.5D03 0.11783 0.05564 0.00406 0.00783 104.7
@ 15 204.91120819 2.5D03 0.11469 0.05419 0.00396 0.00762 112.6
@ 16 204.90881147 2.4D03 0.11169 0.05280 0.00388 0.00743 121.1
@ 17 204.90640494 2.4D03 0.10873 0.05144 0.00390 0.00747 128.4
@ 18 204.90411816 2.3D03 0.10596 0.05017 0.00374 0.00713 135.9
@ 19 204.90189926 2.2D03 0.10331 0.04896 0.00367 0.00694 142.7
@ 20 204.89974575 2.2D03 0.10077 0.04780 0.00360 0.00677 149.3
@ 20 204.89974575 2.2D03 0.10077 0.04780 0.00360 0.00677 149.3
EDIT: In case it matters, these results were obtained with the latest NWChem snapshot: http://www.nwchemsw.org/download.php?f=Nwchemdev.revision25716src.20140609.tar.gz
I compiled using OpenBLAS 0.28 as BLAS and was running under 64 bit Ubuntu 14.04.

Edited On 6:59:50 PM PDT  Wed, Jul 9th 2014 by Mernst




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


Forum Vet
Threads 9
Posts 1404


8:53:42 AM PDT  Thu, Jul 10th 2014 

Matt
Thanks for the bug report.
The gradient generated with 'grid nodisk' and rodft/cgmin are incorrect.
A fix has been checked into the svn repository

Edited On 2:01:09 PM PDT  Thu, Jul 10th 2014 by Edoapra



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