On Mon, Nov 14, 2022 at 5:20 AM Victor Nazarychev <[email protected]> wrote:
>
> Dear Christoph,
>
> I tried parameterising non-bonded interaction in composite systems with 
> stacks containing the polymer (C-type beads) and graphene-like molecules 
> (A-type beads).
>
> To understand in what range, I should conduct force calculations, first I 
> calculated the target distribution A-A, A-C, C-C, please see 
> fig.SYS_all_targets.jpg.
>
> From these distributions, I understand that I should calculate the forces in 
> the range from 0 to 4 ns. Then, using settting_fm2.xml I started a 
> force-matching procedure. However, for C-C interactions, I got infinity
>
> #### Force matching residual ####
>      Chi_2[(kJ/(mol*nm))^2] = -nan
> #################################
>
> This should be a number: -nan
> This should be a number: -7.13506
> This should be a number: -6.01957
>
> I changed the ranges in which I calculated the forces (from 0 to 2, 3 or 3.5 
> nm). Nevertheless, for the C-C interactions, the number was NAN.
>
> Maybe I should change some parameters in the setting file? Or should I 
> increase the box size?
I am not the force-matching expert, so I will have to think about this
a bit more carefully, but I am assuming the error is an artifact from
the fact that the system isn't uniform.

Christoph

>
> Best wishes,
>
> Victor
>
> <cg>
>
>   <fmatch>
>     <!--Number of frames for block averaging -->
>     <frames_per_block>6</frames_per_block>
>     <!--Constrained least squares?-->
>     <constrainedLS>0</constrainedLS>
>   </fmatch>
>
>     <non-bonded>
>         <name>C-C</name>
>         <type1>C</type1>
>         <type2>C</type2>
>         <fmatch>
>             <min>0.0</min>
>             <max>4.0</max>
>                   <step>0.01</step>
>                   <out_step>0.005</out_step>
>         <res_output_coeff>5</res_output_coeff>
>         </fmatch>
>     </non-bonded>
>
>     <non-bonded>
>         <name>A-A</name>
>         <type1>A</type1>
>         <type2>A</type2>
>         <fmatch>
>             <min>0.0</min>
>             <max>4.0</max>
>                   <step>0.01</step>
>                   <out_step>0.005</out_step>
>         <res_output_coeff>5</res_output_coeff>
>         </fmatch>
>     </non-bonded>
>
>         <non-bonded>
>         <name>A-C</name>
>         <type1>A</type1>
>         <type2>C</type2>
>         <fmatch>
>             <min>0.0</min>
>             <max>4.0</max>
>                   <step>0.01</step>
>                   <out_step>0.005</out_step>
>         <res_output_coeff>5</res_output_coeff>
>         </fmatch>
>     </non-bonded>
>
>
> </cg>
>
> пятница, 11 ноября 2022 г. в 10:35:24 UTC+3, Victor Nazarychev:
>>
>> Dear Christoph,
>>
>> Thank you very much.
>>
>> чт, 10 нояб. 2022 г. в 19:30, Christoph Junghans <[email protected]>:
>>>
>>> On Thu, Nov 10, 2022 at 5:01 AM Victor Nazarychev <[email protected]> 
>>> wrote:
>>> >
>>> > Dear Cristoph,
>>> >
>>> > Thank you for your help.
>>> >
>>> > среда, 9 ноября 2022 г. в 22:52:45 UTC+3, Christoph Junghans:
>>> >>
>>> >> On Wed, Nov 9, 2022 at 11:48 AM Victor Nazarychev <[email protected]> 
>>> >> wrote:
>>> >> >
>>> >> > Dear Votca users,
>>> >> >
>>> >> > I try to parametrize the non-bonded intecations in CG model using the 
>>> >> > ibi procedure for graphene molecules. However, when I build 
>>> >> > nanocomposite comprises polymer and graphene flakes is atomostic 
>>> >> > simulation stacks are formed between the graphene flakes. In this 
>>> >> > case, the target pair distribution function between CG atoms in 
>>> >> > graphene falls to 1 only on the end of box. please see the attached 
>>> >> > file.
>>> >> >
>>> >> > If I undesrtand it is imposible to acurate calculate potential between 
>>> >> > the atoms in stacks using ibi procedure due to the fact the rdf does 
>>> >> > not fall to one.
>>> >> There are re-weighting techniques for these kind of systems, e.g. see
>>> >> https://doi.org/10.1063/1.4742067
>>> >>
>>> > I have a couple of clarifying questions. I did not find re-weighting 
>>> > techniques in the VOTCA, as I understand this approach has not been 
>>> > implemented yet?
>>> Correct and most likely it will never get added. You will have to
>>> overwrite the RDF calculator script with something that works for your
>>> special case.
>>>
>>> >>
>>> >> > However, could I calculate in some case this like potential for CG 
>>> >> > model with help of the force-matching?
>>> >> I think force-matching could work as well.
>>> >>
>>> >
>>> > If I use bonded potentials calculated by the ibi procedure, will 
>>> > calculating only nonbonded potentials with the help of force-matching be 
>>> > correct for my model? Or should I parametrize bonded and non-bonded 
>>> > potential together by means of force-matching?
>>>
>>> That depends on the system, so I don't know.
>>> We mixed IB/IBI with force-matching in this paper
>>> http://dx.doi.org/10.1002/mats.201100011 and it worked, but that isn't
>>> a guarantee it will work for your system.
>>> IBI reproduces the effective PMF while FM reproduces the average
>>> force, which is not always the same.
>>>
>> If I understand the procedure csg_fmatch is not paralleled and can be used 
>> in single processor mode only?
>>
>>
>> Best regards.
>> Victor
>>
>>>
>>> Christoph
>>>
>>> >
>>> > Best regards,
>>> > Victor
>>> >
>>> >>
>>> >> Christoph
>>> >> >
>>> >> > Best regards,
>>> >> > Victor
>>> >> >
>>> >> > --
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>>> >>
>>> >>
>>> >>
>>> >> --
>>> >> Christoph Junghans
>>> >> Web: http://www.compphys.de
>>> >
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>>>
>>>
>>> --
>>> Christoph Junghans
>>> Web: http://www.compphys.de
>>>
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-- 
Christoph Junghans
Web: http://www.compphys.de

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