[CP2K-user] [CP2K:12201] Re: PM6

[B Goldf]

Dear Thomas,
Vielen Dank !
Grüße Bernd


On Wednesday, September 11, 2019 at 11:26:49 AM UTC+2, tkuehne wrote:
>
> Dear Bernd, 
>
> „FM“ stands for force-matched. It is a PM6 custom parametrization for 
> aqueous systems obtained by force matching to MP2 water clusters. 
> Please see: https://onlinelibrary.wiley.com/doi/abs/10.1002/jcc.23887
>
> Cheers, 
> Thomas
>
> Am 11.09.2019 um 10:28 schrieb B Goldf <jog... at gmail.com <javascript:>
> >:
>
> Dear Teo,
>
> besides PM6, PM6-FM is implemented in CP2K6.1.
> Do you know which modification "FM" makes?
> Is there some reference for PM6-FM?
>
> Many thank
> Bernd
>
>
>
>
> On Wednesday, April 30, 2008 at 5:36:50 PM UTC+2, Teo wrote:
>>
>> Dear All,
>>
>> good news:
>> with the today commit, (finally !!), there's the possibility to run  
>> PM6 semi-empirical calculation in
>> CP2K (fully support for all elements) (at the moment only numerical  
>> derivatives.. analytical will come soon).
>>
>> bad news:
>> In the original version of PM6 there are some terms that make the  
>> heat of formation a discontinuous function of
>> the nuclei positions (are just correction terms, constants that  
>> become zero for different topological configurations) that
>> we didn't implement. Therefore for few situations there could be  
>> discrepancies between the heat of formation of CP2K
>> and the one of MOPAC (but the electronic energy should anyway be the  
>> same (within numerical  errors (see below)).
>> An example is H-CC-H, that has a constant correction term to the heat  
>> of formation of the triple bond that becomes
>> zero when the triple bond is broken (it's just a step function).
>>
>> Why have been these terms omitted?
>> Simply because there's no trace of them in the PM6 paper.
>>
>> I'm sure that there could be other hidden corrections/parameters not  
>> explicitly mentioned in the paper (classical correction
>> like the one for correcting the sp2 pyramidalization, that we didn't  
>> implement as well), so in case of big discrepancies
>> compared with MOPAC2007 feel free to post here your input file and a  
>> short description of the problem.
>>
>> What does it mean big discrepancies?
>> These are the values for the heat of formation (kcalmol) of the  
>> following systems (CP2K/MOPAC2007)
>>
>> HCl  (17.0356/17.0345)
>> BrCl (2113.534/2113.493)
>> TiO (202.714/202.633)
>>
>> If you have some discrepancy larger than the ones above, check always  
>> the value of the electronic energy that
>> must anyway be VERY similar (the only difference is in the way we  
>> compute integrals.. so just kind of numerical
>> errors, totally negligible).
>> Have fun!!
>>
>> Teo
>>
>>
>>
>>
>>
>>
>>
>>
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> ==============================
> Thomas D. Kühne
> Dynamics of Condensed Matter
> Chair of Theoretical Chemistry
> University of Paderborn
> Warburger Str. 100
> D-33098 Paderborn
> Germany
> td... at mail.upb.de <javascript:>
> +49/(0)5251/60-5726
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