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Re: [lammps-users] Problem with Ackland Analysis
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Re: [lammps-users] Problem with Ackland Analysis

From: Axel Kohlmeyer <akohlmey@...24...>
Date: Fri, 4 May 2018 08:52:09 -0400

On Fri, May 4, 2018 at 5:40 AM, Olivier Politano <olivier.politano@...1102...> wrote:
Dear Lammps users,

We are still working with Lammps 12Apr13. When we perform an ackland analysis with this version of LAMMPS, we obtain the following image for some atomic configuration. BCC atoms are represented in blue and FCC atoms are green.

I went through the file « compute_ackland_atom.cpp » in the USER-MISC directory and I found some modifications between the versions 12Apr13 and 7Dec15 (or later). However, I did not find mentions of these changes in the webpage "Latest Features and Bug Fixes in LAMMPS » or in the source file.

​after a little digging in the git repository and the mailing list archives, i think i have found the origin of the change you noticed in this contribution posted to the mailing list:

it comes with some detailed explanations, so please have a look.

So, I’m wondering if someone also noticed this drastic difference of result for the Ackland analysis and if there is a bug or a problem with the newer implementation of Ackland. 

​that e-mail claims to have removed some issues with the "old" implementation and the changes were approved by the original contributor of compute ackland/atom.

i am copying brian, who contributed these changes, in the hope, that he may be able to comment on his changes and your observations.

and i am also copying alex, the author of ovito in the hope, that he can provide some insight into what algorithm/implementation his code uses and how that stacks up with what the code in LAMMPS does.

it would be fairly easy to roll back the changes, but unless there is some tangible information that can prove what is correct for all cases and where the problem is at the implementation level, it is difficult to make a choice here.





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Dr. Axel Kohlmeyer  akohlmey@...24...
College of Science & Technology, Temple University, Philadelphia PA, USA
International Centre for Theoretical Physics, Trieste. Italy.