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mrkllntschpp / lammps-tutorials

LAMMPS tutorials for Beginners
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How to realize the 110 direction stretching? #1

Closed Dreamer-zh closed 4 years ago

Dreamer-zh commented 4 years ago

Thank you very much for this tutorial. According to this tutorial, I have realized the tensile mechanical properties of BCC(body centered cubic) Fe block (x - < 100 >, Y - < 010 >, Z - < 001 >).

But I couldn't achieve it when I tried the tensile mechanical properties of another crystal oriented Fe block (x - < 110 >, Y - < 110 >, Z - < 001 >). I have tried to modify the system temperature, cutoff and other parameters, but I still can't. I have to ask you for help. I hope you can help me.

Thank you!

Dreamer-zh commented 4 years ago

Other conditions remain unchanged. If I only change this command, the program will report an error. Crystal orientation in tutorial: lattice bcc ${latparam} orient x 1 0 0 orient y 0 1 0 orient z 0 0 1 Crystal orientation after transformation lattice bcc ${latparam} orient x 1 1 0 orient y -1 1 0 orient z 0 0 1

Error: Step Lx Ly Lz Press Pxx Pyy Pzz PotEng Temp 0 28.55 28.55 28.55 2.5124817e+16 3.7687225e+16 3.7687225e+16 -161074.47 1.0947933e+15 300 ERROR: Non-numeric pressure - simulation unstable (../fix_nh.cpp:1043) Last command: run 20000

mrkllntschpp commented 4 years ago

Thanks! It turns out that I had defined the "lattice" command twice and the initial one did not have the details of the orientation, so it defaults to the <100> configuration--this caused a problem because the next command used the periodic distance in those directions to set up the simulation cell boundaries. Then, it built the atoms to the "intended" orientation with the second "lattice" command. This means that it probably built a bunch of atoms at the boundary that made for a weird atom lattice (not single crystal!). So...

I went ahead and moved the "lattice" orientation assignment in Tutorials 1, 2, 3, and 4 before the perioidic distance command. I added an FAQ to Tutorials 1 and 3 about how to do this. Voila! Issue resolved. Not a problem necessarily for <100>, but now it should be easily changed to new orientations.