From NWChem
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| 1:33:45 AM PDT - Sun, May 18th 2014 |
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In src/tce/tce_input.F I see that there are handlers for "qcisd(t)" and "cr-qcisd(t)". I took QA/tests/tce_h2o/mp4sdq_h2o.nw and replaced
tce
mbpt4(sdq)
end
with
tce
qcisd(t)
end
and the modified input file appeared to run successfully, i.e. it produced a number that looked reasonable and didn't crash during execution.
But I don't know if it is really ready for use since the manual doesn't mention QCISD(T):
http://www.nwchem-sw.org/index.php/TCE
I am interested in implementing the Gaussian-n composite thermochemical methods. I want to be able to treat open shell molecules so the implementations in GAMESS and Psi4 are currently inadequate; both require RHF reference functions for their QCISD(T) functionality. If there's something weird about the QCISD(T) functionality implemented through the TCE I don't have a second program to double-check calculations on open shell molecules using it.
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Edited On 1:41:14 AM PDT - Sun, May 18th 2014 by Mernst
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| 8:58:00 AM PST - Wed, Dec 10th 2014 |
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Quote:Mernst May 18th 8:33 amIn src/tce/tce_input.F I see that there are handlers for "qcisd(t)" and "cr-qcisd(t)". I took QA/tests/tce_h2o/mp4sdq_h2o.nw and replaced
tce
mbpt4(sdq)
end
with
tce
qcisd(t)
end
and the modified input file appeared to run successfully, i.e. it produced a number that looked reasonable and didn't crash during execution.
But I don't know if it is really ready for use since the manual doesn't mention QCISD(T):
http://www.nwchem-sw.org/index.php/TCE
I am interested in implementing the Gaussian-n composite thermochemical methods. I want to be able to treat open shell molecules so the implementations in GAMESS and Psi4 are currently inadequate; both require RHF reference functions for their QCISD(T) functionality. If there's something weird about the QCISD(T) functionality implemented through the TCE I don't have a second program to double-check calculations on open shell molecules using it.
That code might be correct. I recall that (T) is the same for QCISD and CCSD. It should be valid to run the (T) code with QCISD amplitudes.
I am surprised that QCISD(T) for open-shell systems cannot be verified via CFOUR. Can you verify this?
In any case, QCISD(T) only has a quadratic singles term and thus I think CCSD(T), which has higher-order singles terms, should be much more accurate for open-source systems. QCISD(T) for open-shell and multi-reference systems is a known problem in the literature.
In the event you find an error in NWChem, please contact me and I will try to debug the issue. My email address is found on http://jeffhammond.github.io/.
Best,
Jeff
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Edited On 9:00:30 AM PST - Wed, Dec 10th 2014 by Jhammond
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Gets Around
Threads 11
Posts 98
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| 1:23:56 PM PST - Wed, Dec 10th 2014 |
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CFOUR may well offer this functionality for comparison. In the past I signed dozens of academic software license agreements, nowadays I have license agreement fatigue. Perhaps I should to endure it one more time.
QCISD(T) surely does not offer the best accuracy for its cost among current methods, but it is needed to reproduce historical work. Calculations that required long jobs on expensive hardware 20 years ago are now easily completed on a laptop, if the software support is there. My ultimate motivation is that I don't think people should have to pay $$$$ to G******* Inc just to reproduce literature results from the 1980s and 1990s. In any case I only get to work on this problem in dribs and drabs of spare time, so progress is slow.
Thank you for the response. I have learned a lot from your mailing list posts and web pages in the past.
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