[CP2K:8553] error in computing dissociation energy

[hut... at chem.uzh.ch]

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]