[CP2K:8553] error in computing dissociation energy

Vladimir Rybkin rybk... at gmail.com
Wed Jan 18 12:34:16 CET 2017


Once again:
ADF uses Slater-type orbitals, STO, (and no pseudopotentials). STOa are 
more compact than Gaussians, smaller basis sets are needed for accurate 
energies. So, you have:
1) pseudo/no pseudo
2) really different basis sets (and you don't specify which have been used 
in ADF), which are a major source of discrepancies. In your table I see 
that for CH3-CH3 ADF gives a number 4 times larger than CP2K and the 
reference ...

Yours,

Vladimir

среда, 18 января 2017 г., 12:11:36 UTC+1 пользователь katarína stančiaková 
написал:
>
> Thank you for the prompt reply,
> just to explain: I performed two sets of tests: 
> 1) I used example input files from CP2K to check if I get the same numbers 
> as in the TEST_FILES (That's reason why I used SZV basis set there). 
>
> 2) I tested above mentioned reactions always with the same basis set 
> (TZVP-MOLOPT), box size, poison solvers, convergence criteria, etc. So I 
> don't think that this might be a problem.
> Since I thought that pseudopotential could be "the problem" I tried to 
> calculate reaction enthalpy of another simple system: 2CO2 -> 2CO + O2 
> (using the same settings as for previous reactions) and again compared 
> results with ADF. The difference was about 16 kcal/mol, so I am a bit 
> surprised that using pseudopotentials might result in a so large 
> disagreement on such a small systems. 
>
>
> Best,Katarina
>
>
> Dňa streda, 18. januára 2017 11:45:30 UTC+1 jgh napísal(-a):
>>
>> Hi 
>>
>> to add to the post of Vladimir: 
>>
>> Be careful with the basis sets (SZV is not reasonable in CH4). 
>> Be consistent: use the same box and cutoff and Poisson solver for all 
>> molecules. 
>> Be aware that pseudopotentials are known to have problems when 
>> comparing energies for systems with different spin multiplicities. 
>>
>> regards 
>>
>> Juerg 
>> -------------------------------------------------------------- 
>> Juerg Hutter                         Phone : ++41 44 635 4491 
>> Institut für Chemie C                FAX   : ++41 44 635 6838 
>> Universität Zürich                   E-mail: hut... at chem.uzh.ch 
>> Winterthurerstrasse 190 
>> CH-8057 Zürich, Switzerland 
>> --------------------------------------------------------------- 
>>
>> -----cp... at googlegroups.com wrote: -----To: cp2k <cp... at googlegroups.com> 
>>
>> From: katarína stančiaková 
>> Sent by: cp... at googlegroups.com 
>> Date: 01/17/2017 02:07PM 
>> Subject: [CP2K:8553] error in computing dissociation energy 
>>
>> 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 ->                    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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>>
>> [attachment "CH4-PBE0_TC_LRC.inp" removed by Jürg Hutter/at/UZH] 
>> [attachment "CH4-PBE0_TC_LRC.out" removed by Jürg Hutter/at/UZH] 
>> [attachment "geo_opt_isopropyl.inp" removed by Jürg Hutter/at/UZH] 
>> [attachment "geo_opt_isopropyl.out" removed by Jürg Hutter/at/UZH] 
>> [attachment "Results.pdf" removed by Jürg Hutter/at/UZH] 
>>
>
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