Erratic "fix move linear x y z" behavior

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1

Hello!

At this moment, I am trying to simulate a deformation behavior of Nickel polycrystal.

Problems

  1. Since I used “s s s” non-periodic boundary condition, explicit movement must be applied.
  2. However, “fix move” shows a erratic behavior that suddenly jumps from certain point.

Brief explanation for simulation

  1. Polycrystal has been generated by “atomsk”.
  2. Generated polycrystal was processed by LAMMPS input script to shape specimen.
  3. generated polycrystal equilibrated under “s p s” boundary condition, with NPT ensenble.
  4. boundary condition changed to “s s s” condition
  5. “fix move” applied into small region in the end of each side of y-axis
  6. nve integration applied, and run 100,000 steps

Log

Per MPI rank memory allocation (min/avg/max) = 22.82 | 23.35 | 23.88 Mbytes

Step Lx Ly Lz Press Pxx Pyy Pzz PotEng Temp v_stanum
0 266.09915 883.10215 33.000145 -197.3738 -114.23973 -290.35889 -187.52279 -1421316.7 300.88052 212606
1 266.09915 883.10215 33.000145 -413.63069 -294.12715 -476.37951 -470.38539 -1419566.5 293.3014 212606
2 266.09915 883.10215 33.000145 -413.05097 -291.83059 -476.05783 -471.26449 -1419565 293.26594 212606
3 266.09915 883.10215 33.000145 -412.40369 -289.48266 -475.61811 -472.1103 -1419563.4 293.22877 212606
4 266.09915 883.10215 33.000145 -411.66387 -287.06674 -475.03305 -472.89181 -1419561.7 293.19018 212606
5 266.09915 883.10215 33.000145 -410.82881 -284.59973 -474.28065 -473.60604 -1419560 293.15045 212606
6 266.09915 883.10215 33.000145 -409.91208 -282.09717 -473.38807 -474.25099 -1419558.3 293.10989 212606
7 266.09915 883.10215 33.000145 -408.92161 -279.56248 -472.3665 -474.83586 -1419556.5 293.06881 212606
8 266.09915 883.10215 33.000145 -407.85431 -277.0028 -471.20248 -475.35764 -1419554.7 293.02757 212606
9 266.09915 883.10215 33.000145 -406.74203 -274.44464 -469.93856 -475.84291 -1419553 292.98648 212606
10 318.91517 905.36291 60.930201 -200.29336 -124.42642 -284.82451 -191.62915 -1420412 292.94598 212606
Loop time of 0.155598 on 8 procs for 10 steps with 331426 atoms

after that, I’ve changed the script to separate run by two.

as you can see in below,

2

Hello!

At this moment, I am trying to simulate a deformation behavior of Nickel polycrystal.

Problems
1. Since I used "s s s" non-periodic boundary condition, explicit movement must be applied.
2. However, "fix move" shows a erratic behavior that suddenly jumps from certain point.

how can we tell? couldn't it be, that you are just using it wrong, or
the system behaves different from what you expect? have you visualized
what happens?

axel.