David Shobe
avidshobe@yahoo.com
Thanks for everyone's patience,
--David Shobe
On Fri Mar 25 '16 0:49am, David Shobe wrote
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>Thanks, Alex. (although now I look for the "search" button and can't see it). Anyway, you wrote, at the link provided:
>> These problematic cases should be further inspected to find out
>> whether MP2 problems are caused by the use of inadequate basis
>> set (and hence, the problems can be solved using better basis
>> set),
>> or are inherent to MP2 (e.g., because of milti-configuration
>> nature of true wavefunction).
>I doubt (although I could be wrong) that simple alkynes require a multireference model. That leaves the basis set. I think of larger basis sets as having more convergence difficulties but there could be exceptions. I would have liked a triple-zeta basis set, but I also would like to be able to put in third-row elements (Ge-Br) and options are limited.
>Anyway, I am only trying to calculate heats of hydrogenation, compared to that of acetylene. (R-CC-R' + CH3-CH3 --> R-CH2-CH2-R' + HCCH). Using MP4/DZV(d,p)++//MP2/DZV(d,p) might actually be overkill for an isodesmic reaction like this. I was in the habit of using CCSD//B3LYP methods (and a different computational chemistry program) for just about everything containing only s- and p- block elements, and it usually worked in a reasonable amount of time. Now I can't use coupled cluster theory with your program (correct?) so I have to be a bit more judicious.
>Regards,
>--David Shobe
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>On Thu Mar 24 '16 10:11pm, Alex Granovsky wrote
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>>Dear David,
>>if you search this site (using "search" button on the left) for mp2 cphf
>>you will find the following link
>>http://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7026-869+00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7026-869+00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7026-869+00.htmhttp://classic.chem.msu.su/cgi-bin/ceilidh.exe/gran/gamess/forum/?C34df668afbHW-7026-869+00.htm
>>Hope this help.
>>Kind regards,
>>Alex Granovsky
>>
>>