[CP2K:3168] Re: error in bond dissociation energy of gas phase molecule

Teodoro Laino teodor... at gmail.com
Wed Apr 6 13:02:12 CEST 2011


Hi Jun,

that's correct - 
Try nonetheless whatever decoupling you like (WAVELET or MT) - I'm quite skeptical on the ANALYTIC one though (so I would never suggest you this one specifically).

H2O2 and H2O have strong dipoles and these may still bias the energetics in full periodic boundary conditions (keep in mind that in a full slab of dipoles the electrostatic interactions falls like 1/r, although for two isolated dipoles the interactions goes like 1/r^3).

Remember to include also:
&CELL
   PERIODIC NONE
..
&END

for your large basis set you may still have some contributions from the NL of the core hamiltonian matrix.

Regards,
Teo

On Apr 6, 2011, at 12:55 PM, Jun wrote:

> Thanks for the prompt reply.
> We are calculating OH radical, rather OH anion. So, all the species
> are neutral.
> Jun
> 
> On Apr 6, 11:53 am, hut... at pci.uzh.ch wrote:
>> Hi
>> 
>> as you are generating charged species you should use a non-periodic
>> steup.
>> 
>> Try PERIODIC NONE in the &CELL section together with
>> 
>>     &POISSON
>>       PERIODIC NONE
>>       PSOLVER WAVELET    <- MT and ANALYTIC could also work but this is best
>>     &END
>> 
>> in the DFT section.
>> 
>> regards
>> 
>> Juerg
>> 
>> --------------------------------------------------------------
>> Juerg Hutter                         Phone : ++41 44 635 4491
>> Physical Chemistry Institute   FAX   : ++41 44 635 6838
>> University of Zurich               E-mail:  hut... at pci.uzh.ch
>> Winterthurerstrasse 190
>> CH-8057 Zurich, Switzerland
>> ---------------------------------------------------------------
>> 
>> -----cp... at googlegroups.com wrote: -----
>> 
>> To: cp2k <cp... at googlegroups.com>
>> From: Jun
>> Sent by: cp... at googlegroups.com
>> Date: 04/06/2011 12:43PM
>> Subject: [CP2K:3165] error in bond dissociation energy of gas phase molecule
>> 
>> Hello everyone,
>> 
>> We did some testing calculations on bond dissociation energies of HO-
>> OH in vacuum using BLYP and B3LYP. We found a large difference from
>> reported results using the same functionals in literature; our numbers
>> are about 0.5 eV too small for both functionals. We also cross-checked
>> the numbers using gaussian program, indeed cp2k gives smaller bond
>> dissociation energy. It is not likely to be BSSE, as we use quite
>> large basis set TZV2P and also checked QZV2P. It is obvious that we
>> got either the total energy of H2O2 too high or the OH energy too low.
>> We checked the energy of H2O --> OH + H, which is very close to what
>> we found in literature. So, the problem appears to be the too high
>> energy of H2O2.
>> Also, we checked CH3-CH3, and found the same: CH3-CH3 bond
>> dissociation energy is 0.3 eV too small for both functionals compared
>> to literature numbers, while the energy of CH4-->CH3+H agrees well.
>> The bond dissociation energies (total energies without ZPE) are
>> summarised below, and inputs for H2O2-->2OH (H2O2.inp and OH.inp) are
>> uploaded.
>>                                 BLYP             B3LYP
>> H2O2-->2OH       2.04 eV (2.67)      1.80 eV  (2.27)
>> H2O-->OH+H        5.10 eV              5.16 eV (5.2)
>> C2H6-->2CH3     3.64 eV (3.92)       3.69 eV (3.97)
>> CH4-->CH3+H    4.69 eV (4.77)       4.75 eV (4.67)
>> Numbers in parentheses are from literature. The geometry is optimised
>> one taken from literature, which is almost the same as optimised by
>> cp2k.
>> Can anyone comment on this? Many thanks in advance.
>> 
>> Cheers,
>> Jun
>> 
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