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Re: [lammps-users] [lammps-Users]Script to check Single layer graphene deformation in x direction
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Re: [lammps-users] [lammps-Users]Script to check Single layer graphene deformation in x direction


From: sumit nagar <sn971489@...24...>
Date: Tue, 10 Oct 2017 07:26:25 +0530

Hello everyone,

I have used quartic bond style as it uses the potential to define a
bond which can be broken . In the attached movie file the bonds are
getting broken but my concern here is the fracture should propagate by
a crack initiation .Am i missing a important check here? The data file
and script file are attached herewith also the simulation has been
done at 0 kelvin .The script uses lennard jones potential.

I am also self training on MD simulation as research and training
facilities are not present in India . I am from India and i am quite
new to lammps .
Sumit ,Nagar
M.Tech (Production engg)
B.E (Production and Ind Engg)
MCSA 70-290 ,SQL (Oracle z -007)
ITIL certified ,MCAD 70-306
GATE 2006,2013<div id="DAB4FAD8-2DD7-40BB-A1B8-4E2AA1F9FDF2"><br />
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Sumit ,Nagar
M.Tech (Production engg)
B.E (Production and Ind Engg)
MCSA 70-290 ,SQL (Oracle z -007)
ITIL certified ,MCAD 70-306
GATE 2006,2013


On Mon, Oct 9, 2017 at 2:34 PM, sumit nagar <sn971489@...24...> wrote:
> Hello everyone,
>
> I have used quartic bond style as it uses the potential to define a
> bond which can be broken . In the attached movie file the bonds are
> getting broken but my concern here is the fracture should propagate by
> a crack initiation .Am i missing a important check here? The data file
> and script file are attached herewith also the simulation has been
> done at 0 kelvin .The script uses lennard jones potential.
>
> I am also self training on MD simulation as research and training
> facilities are not present in India . I am from India and i am quite
> new to lammps .
> Sumit ,Nagar
> M.Tech (Production engg)
> B.E (Production and Ind Engg)
> MCSA 70-290 ,SQL (Oracle z -007)
> ITIL certified ,MCAD 70-306
> GATE 2006,2013
>
> ---------- Forwarded message ----------
> From: Axel Kohlmeyer <akohlmey@...24...>
> Date: Tue, Sep 26, 2017 at 8:31 PM
> Subject: Re: [lammps-users] [lammps-Users]Script to check Single layer
> graphene deformation in x direction
> To: sumit nagar <sn971489@...24...>
>
>
> i'm taking this offline out of courtesy (see below).
>
> On Tue, Sep 26, 2017 at 8:34 AM, sumit nagar <sn971489@...24...> wrote:
>> Dear lammps users ,
>>
>> Attached is my script for deformation of single layer graphene inside a
>> simulation box.The main point which i want to see here is fracture of
>> graphene .I have remapped the coordinate in x to group it inside a
>> deformation box .I have used COMPASS force field for my simulation .I have
>> also taken a fairly large time for the simulation but the graphene appears
>> like a rubber band it continues to stretch without showing fracture .Can
>> anyone please tell me what i am missing in my script.I will be highly
>> grateful to you .
>
> you are missing almost everything that is important, your input looks
> like it is copied together from bits and pieces and lots of them are
> inconsistent.
> you are wasting your time and the time of everybody on this list
> reading your message. getting an MD code to run an input is easy;
> setting up a meaningful simulation not so much.
>
> you need *in person* tutoring in general MD basics and supervision.
> you need understanding of force fields and how to set up MD
> calculations that have meaning. this is not something you can learn by
> copying random bits from a manual and by asking a mailing list for
> help and explanations. you already have asked for introductory and
> tutorial material and have been given useful advice, yet you don't
> appear to have been able to learn from it. this is an indication, that
> you don't have sufficient prerequisite knowledge.
>
> more specifically, in your input deck there is no time integration,
> there is no equilibration, your force field parameters are obviously
> bogus, your claim that this is COMPASS is incorrect (apart from the
> off-the-chart non-bonded parameters, there is no bond topology, and no
> matching bond/angle/dihedral and styles and parameters. besides with
> default settings, bonds in COMPASS or other conventional force fields
> cannot break), you are ignoring important warnings that LAMMPS prints.
>
> the only thing your input is doing is to uniformly stretch your system
> while essentially ignoring the forces you compute. you could pick any
> force field, any pair style, any set of parameters, and you would see
> *exactly* the same trajectory. this is not a LAMMPS issue or a topic
> for lammps-users. this is a problem of you not knowing what you are
> doing.
>
> be smart, take the hint, talk to your adviser/supervisor, and ask for
> help to get properly trained for your research.
> if you continue your current path, you are heading for public embarrassment.
>
> axel.
>
>
>
>>
>> Regards,
>> Sumit ,Nagar
>> M.Tech (Production engg)
>> B.E (Production and Ind Engg)
>> MCSA 70-290 ,SQL (Oracle z -007)
>> ITIL certified ,MCAD 70-306
>> GATE 2006,2013
>>
>> ------------------------------------------------------------------------------
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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.
>
>
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