[CP2K:8553] error in computing dissociation energy
rybk... at gmail.com
Wed Jan 18 12:34:16 CET 2017
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
среда, 18 января 2017 г., 12:11:36 UTC+1 пользователь katarína stančiaková
> 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.
> Dňa streda, 18. januára 2017 11:45:30 UTC+1 jgh napísal(-a):
>> 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
>> Be aware that pseudopotentials are known to have problems when
>> comparing energies for systems with different spin multiplicities.
>> 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:
>> 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
>> 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
>> Thank you for any help
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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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