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Re: [lammps-users] Fwd: pcff force field
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Re: [lammps-users] Fwd: pcff force field


From: Andrew Jewett <jewett@...1937...>
Date: Wed, 23 Aug 2017 20:19:36 -0700

Currently, it's difficult to use PCFF.

EMC (or msi2lmp+MaterialsStudio) might be your only options.  However,
unfortunately both PCFF and CVFF use a complicated system
"auto_equivalences" for looking up force field parameters according to
atom type.  "msi2lmp" does not handle these correctly, and I suspect
EMC might not either, but I could be wrong.  (Please correct me if I'm
wrong.  People have complained to me about using both tools with PCFF
force field.)

About 6 months ago, we attempted to convert COMPASS PCFF and CVFF into
moltemplate format, but it was taking a lot of time to figure out how
to handle "auto_equivalences" correctly.  (A LOT of time.  A -month-
of time devoted to this specific issue.)
http://lammps.sandia.gov/threads/msg66954.html
With Marcus Martin's help, I think we figured out how to solve the
issue I still probably need another week to get this working, and I
have other projects of much greater urgency (which threaten my
livelihood) to work on.  I hope to get this working some time early
next year when things have settled down.

If you want to use a class2 force field, perhaps you will have better
luck with COMPASS.  For now, try using EMC (or msi2lmp) with the
compass force field.  COMPASS does not use "auto_equivalences"

Good luck

Andrew



On Wed, Aug 23, 2017 at 7:58 PM, Vanessa Oklejas <voklejas@...24...> wrote:
> Please, always email the lammps user list when responding.
>
> What version of lammps are you using? I believe the most current stable
> version for download (17 August 2017) lists a force field file (*.frc) for
> pcff in ./tools/msi2lmp/frc_files/. So I imagine that producing a
> lammps-style data files using types from the pcff force field should be
> possible. There are a few places where you might run into stumbling blocks
> that I can think of off the top of my head: (1) I think pcff is a class 2
> type force field, which I think requires a special flag when you invoke
> msi2lmp. (2) It's possible MS might have additional atom types in their
> version of pcff that are not present in the pcff.frc file that is part of
> the lammps distribution.
>
> ---------- Forwarded message ---------
> From: Rajesh <creativeidleminds@...24...>
> Date: Wed, Aug 23, 2017 at 7:37 PM
> Subject: Re: [lammps-users] pcff force field
> To: Vanessa Oklejas <voklejas@...24...>
>
>
> Dear Vanessa,
> I tried with msi2lmp tool but it is inconsistent with pcff force field. Cant
> we use vmd or moltemplate for the same?
>
> On Wed, Aug 23, 2017 at 10:55 PM, Rajesh <creativeidleminds@...24...>
> wrote:
>>
>> Thank you Vanessa, will give it a try.
>>
>> On Wed, Aug 23, 2017 at 10:28 PM, Vanessa Oklejas <voklejas@...24...>
>> wrote:
>>>
>>> See the msi2lmp tool located in the tools directory of your LAMMPS
>>> package. You need to build this tool before you use it, but that's
>>> relatively straightforward. See the README file in the msi2lmp directory for
>>> specific instructions.
>>>
>>> On Wed, Aug 23, 2017 at 9:50 AM Rajesh <creativeidleminds@...24...>
>>> wrote:
>>>>
>>>> Dear Dr Shan
>>>>
>>>> Thank you for your reply. Is there any tool that can convert material
>>>> studio files to lammps input with all coefficients defined automatically.?
>>>>
>>>>
>>>> Thanks
>>>>
>>>> On Wed, Aug 23, 2017 at 10:12 PM, Ray Shan <rshan@...1795...>
>>>> wrote:
>>>>>
>>>>> Like anyother valence force fields, pcff is invoked via a combination
>>>>> of pair, bond, angle, dihedral, and improper styles.  Pcff belongs to the
>>>>> class2 family, so check the doc page with anything that is “class2”.
>>>>>
>>>>>
>>>>>
>>>>> Ray
>>>>>
>>>>>
>>>>>
>>>>>
>>>>>
>>>>> From: Rajesh <creativeidleminds@...24...>
>>>>> Date: Wednesday, August 23, 2017 at 9:37 AM
>>>>> To: LAMMPS Users Mailing List <lammps-users@lists.sourceforge.net>
>>>>> Subject: Re: [lammps-users] pcff force field
>>>>>
>>>>>
>>>>>
>>>>> Dear lammps users
>>>>>
>>>>>
>>>>>
>>>>> I am trying to simulate a polymer in lammps with pcff. Is there any
>>>>> option for pcff field in lammps? How can I achieve this? I didn't find
>>>>> anything in manual on pcff. Any help will be appreciated. I found some file
>>>>> pcff.frc in lammps folder. I think pcff in not included a pair_style in
>>>>> lammps?
>>>>>
>>>>>
>>>>>
>>>>> Thanks
>>>>>
>>>>>
>>>>>
>>>>> Rajesh
>>>>
>>>>
>>>>
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>>
>
>
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