error in computing dissociation energy

Vladimir Rybkin rybk... at gmail.com
Wed Jan 18 11:33:52 CET 2017


Dear Katarina,

first of all, most results are not that different. 
1) Regarding the literature. Surely, different basis sets have been used. 
Also please note that CP2K employs pseudopotentials. Truhlar has performed 
all-electron calculations. Thus, I would say that the results rather agree, 
than not.
2) As for the tests, there will be some tolerance margin differing on you 
compilation, system etc. So, only the last number looks suspicious, 
although not really.

Yours,

Vladimir

вторник, 17 января 2017 г., 14:07:00 UTC+1 пользователь katarína 
stančiaková написал:
>
> Dear CP2K users,
> I did some basic testing on bond dissociation energies on a small set of 
> molecules using PBE functional.
> I compared my results with literature (
> http://dx.doi.org/10.1007/s00214-007-0401-8 ) and with results obtained 
> using ADF. 
>
> However CP2K results are quite different from my reference and ADF. I 
> tried to play with settings (e.g. turn off the periodicity), but this did 
> not lead to any improvement.
> Afterwards I decided to do some basic testing, using test files. 
> Especially I tested following input files:
>
> /tests/QS/regtest-hybrid-4/CH3-PBE0_TC.inp
> /tests/QS/regtest-hybrid-4/CH3-PBE0_TC_LRC.inp
> /tests/QS/regtest-hybrid-4/CH4-PBE0_TC.inp
> /tests/QS/regtest-hybrid-4/CH4-PBE0_TC_LRC.inp
>
> However, for CH4 case I obtained quite a difference between the numbers 
> given in txt TEST_FILES, where I assume numbers which I should obtain are 
> stores. I tested two versions of CP2K (4.0 and 2.6), and numbers are still 
> the same. Now I am struggling what might be wrong. Please, do you have any 
> suggestions?
>
> Below you can find example of input files and my data
>
> (for all cases we assume homolytic dissociation)
>
> CH3-CH3 -> CH3 + CH3        92.59 (96.79) kcal/mol 
> CH3-OCH3 -> CH3 + OCH3       81.48 (87.24) kcal/mol
> CH3-isopropyl -> CH3 + isopropyl         86.01 (89.65) kcal/mol
> OCH3-isopropyl -> OCH3 + isopropyl                   77.69 (84.08) kcal/mol
>
> Numbers in parentheses are from literature.
>
> The results from testing files:
> CH3-PBE0_TC.inp         -7.98384  (-7.94392) a.u.
> CH3-PBE0_TC_LRC.inp    -7.34353  (-7.34351) a.u.
> cCH4-PBE0_TC.inp        -7.35850  (-7.35848) a.u.
> CH4-PBE0_TC_LRC.inp    -8.00130  (-7.96099) a.u.
> Numbers in parentheses are from corresponding TXT file TEST_FILES 
> (/tests/QS/regtest-hybrid-4/)
>
>
> Thank you for any help
> Best,
> Katarina
>
>
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