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Re: [lammps-users] Difference in results for atomstyle charge and dipole
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Re: [lammps-users] Difference in results for atomstyle charge and dipole


From: John Smith <johnson21smith@...24...>
Date: Thu, 6 Jul 2017 16:47:54 -0500

My simulation keeps stopping because atoms are getting lost during minimization. I tried increasing the size of the domain, yet this is happening. I am attaching the log and input file.

On 6 July 2017 at 16:32, Axel Kohlmeyer <akohlmey@...24...> wrote:
On Thu, Jul 6, 2017 at 5:29 PM, John Smith <johnson21smith@...24...> wrote:
> Thank you, it works now! I am getting a warning saying that kpsace is being
> invoked when there are no charges present. This is true since my input
> consists only of dipoles. Is it still necesary for me to use kspace_style?

if you use a "/long" style, yes. for dipole-dipole interactions only,
it might be acceptable to use lj/cut/dipole/cut or lj/sf/dipole/sf
instead and forego the long-range electrostatic handling. but that is
up to you to decide what is handling the interactions of your system
sufficiently accurate.

axel.

>
> Thanks,
> John
>
> On 6 July 2017 at 15:18, Axel Kohlmeyer <akohlmey@...24...> wrote:
>>
>> On Thu, Jul 6, 2017 at 4:14 PM, John Smith <johnson21smith@...24...>
>> wrote:
>> > In order to do this, I had to change the dimension to 3d and changed the
>> > lattice from sq to sc and boundary p p f. Since I cannot enforce2d in a
>> > 3d
>> > simulation, how do I zero out forces and velocities in z direction?
>>
>> velocity command and then fix setforce?
>>
>> axel.
>>
>> >
>> >
>> >
>> > On 6 July 2017 at 13:29, Axel Kohlmeyer <akohlmey@...24...> wrote:
>> >>
>> >> On Thu, Jul 6, 2017 at 2:27 PM, John Smith <johnson21smith@...24...>
>> >> wrote:
>> >> > I looked into the documentation and updated the pair_style to
>> >> > lj/cut/dipole/long to account for dipole-dipole interactions. I also
>> >> > changed
>> >> > from 'fix nve' to 'fix nve/sphere update dipole'. The documentaion
>> >> > said
>> >> > that
>> >> > I need to include
>> >> >
>> >> > kspace_style ewald/disp 1e-4
>> >> >
>> >> > But I am getting an error that that command cannot be used in a 2D
>> >> > simulation. How do I effectively make this into a 3D simulation and
>> >> > get
>> >> > the
>> >> > same results? Or can is there a workaround to getting the above
>> >> > command
>> >> > working in 2d?
>> >>
>> >> please see kspace_modify slab.
>> >>
>> >> axel.
>> >>
>> >> >
>> >> > Thanks,
>> >> > John
>> >> >
>> >> > On 5 July 2017 at 18:05, Axel Kohlmeyer <akohlmey@...24...> wrote:
>> >> >>
>> >> >> On Wed, Jul 5, 2017 at 6:39 PM, John Smith
>> >> >> <johnson21smith@...24...>
>> >> >> wrote:
>> >> >> > Hello,
>> >> >> >
>> >> >> > I am attaching two input scripts, one with a mixture SRD of style
>> >> >> > charge
>> >> >> > (initial charge set to 0.0) and the other with a net dipole of 1.0
>> >> >> > (in
>> >> >> > reduced lj units). I expected to see an effect due to electric
>> >> >> > field
>> >> >> > on
>> >> >> > the
>> >> >> > system in the case of dipole, but I am not able to observe any
>> >> >> > difference
>> >> >> > between the results of the two runs. I am also attaching the
>> >> >> > graphs
>> >> >> > for
>> >> >> > vacf, msd and diffusion coeffcient calculated using msd.
>> >> >> >
>> >> >> > I have used fix efield, but I am not sure if it is being called?
>> >> >>
>> >> >> as the fix efield documentation states, fix efield adds a torque to
>> >> >> particles with a (point) dipole.
>> >> >> however, there is nothing in your input, that is in any way reacting
>> >> >> to this torque (or to the dipole outside of fix efield).
>> >> >>
>> >> >> axel.
>> >> >>
>> >> >> > Any advice please?
>> >> >> >
>> >> >> > Sincerely,
>> >> >> > John
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> >
>> >> >> > ------------------------------------------------------------------------------
>> >> >> > Check out the vibrant tech community on one of the world's most
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>> >> >> > _______________________________________________
>> >> >> > lammps-users mailing list
>> >> >> > lammps-users@...396...sourceforge.net
>> >> >> > https://lists.sourceforge.net/lists/listinfo/lammps-users
>> >> >> >
>> >> >>
>> >> >>
>> >> >>
>> >> >> --
>> >> >> 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.
>> >> >
>> >> >
>> >>
>> >>
>> >>
>> >> --
>> >> 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.
>> >
>> >
>>
>>
>>
>> --
>> 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.
>
>



--
Dr. Axel Kohlmeyer  akohlmey@...43...4...  http://goo.gl/1wk0
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.

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