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Re: [lammps-users] Fix deform and Stress Strain Plots
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Re: [lammps-users] Fix deform and Stress Strain Plots


From: Axel Kohlmeyer <akohlmey@...24...>
Date: Mon, 23 Apr 2018 13:57:15 -0400

On Mon, Apr 23, 2018 at 1:50 PM, Steve Plimpton <sjplimp@...24...> wrote:
> Fix deform also by default remaps the atoms into the expanding box.
> See the "remap" option.  For a periodic box this is typically
> what you want, else you will have really long across the periodic
> boundaries.

doesn't this apply primarily to a shearing deformation?

for uniaxial expansion, i thought it would be simply the interaction
of the atoms among themselves and across the periodic boundaries, that
would ultimately lead to the strain, although that is usually
accelerated through scaling positions evenly when the box is expanded,
which would be controlled by the dilate option, if i remember
correctly.

axel.

>
> Steve
>
> On Fri, Apr 20, 2018 at 11:14 PM, MASATO KOIZUMI <mkoizumi@...3709...> wrote:
>>
>> Dear LAMMPS Users,
>>
>> Hello. I had a question regarding the fix deform command.
>>
>> I have a simulation box that contains crosslinked polymer chains, and if I
>> apply uniaxial elongation to the the box under NVT ensemble, I obtain a
>> stress strain plot.
>>
>> However, the stress strain plot is a result of elastic energy being stored
>> in the bonds of polymer chains. If fix deform command is simply changing the
>> simulation box size/volume, how is changing the box size related to storing
>> elastic energy in the chain bonds? That is, what exactly is it that pulls
>> the polymer chains when you simply deform a the shape of a box?
>>
>> In OVITO, I see that chains are elongating, but how are the chains
>> elongating when the box elongates? Are the force being applied to the beads
>> that cross the box face that is orthogonal to the direction of the uniaxial
>> loading?
>>
>> I would greatly appreciate if you could provide me with any comments.
>> Thank you.
>>
>> Sincerely,
>>
>> Masato Koizumi
>>
>>
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>
>
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-- 
Dr. Axel Kohlmeyer  akohlmey@...24...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.