Several days ago i asked you a question about heating a non-periodic bicrystal with boundary condition psp to a certain temperature without boundary vanishing, the heated bicrystal is intended to simulate grain boundary mobility using the “ fix orient/fcc” command. The reason of choosing psp boundary is to avoid effect of the upper and low boundaries on motion of the middle grain boundary, but after tried many times, i still can not find a right method to heat the psp boundary without boundaries vanishing, so i use the ppp bicrystal to compute gb mobility for no boundary vanishing when heating ppp bicrystal.
But now i meet a new problem, it may be against attribute of periodic boundary when using the ppp bicrystal. Here i briefly describe my problem. According to doc of Lammps, the essence of the “fix orient/fcc” command is to impose a crystal orientation-dependent driving force on atoms, and only atoms near boundaries suffer such force, then atoms near the upper, middle and low boundaries will move. While motion of atoms near the upper and low boundaries will effect the motion of atoms near the middle boundary, which is used to calculate the gb mobility, so I have to constrain atoms near these two boundaries to move. Here is my approach: in order to avoid the effect of the upper and low boundaries on mobility calculation, i set atoms near these two boundaries to be still by not imposing driving force on all these atoms. According to my understanding of periodic boundary, if boundary condition perpendicular to grain boundary is set to be ‘p’, then atoms near the upper and low boundaries should suffer driving force as atoms near the middle boundary do, i.e. the upper and low boundaries should move as the middle boundary does. So i want to know whether my approach goes against attribute of periodic boundary.
Thanks in advance.
Several days ago i asked you a question about heating a non-periodic bicrystal with boundary condition psp to a certain temperature without boundary vanishing, the heated bicrystal is intended to simulate grain boundary mobility using the “ fix orient/fcc” command. The reason of choosing psp boundary is to avoid effect of the upper and low boundaries on motion of the middle grain boundary, but after tried many times, i still can not find a right method to heat the psp boundary without boundaries vanishing, so i use the ppp bicrystal to compute gb mobility for no boundary vanishing when heating ppp bicrystal.
as i was trying to point out before. ignoring and bypassing a problem
doesn't make it go away.
if your system cannot sustain a grain boundary unless enforced by
symmetry and finite size,
then there is a principal problem that will taint all other results.
please don't bother me with
any questions about this issue, unless you have resolved the more
fundamental problem.
you are just wasting your and everybody other's time.
But now i meet a new problem, it may be against attribute of periodic boundary when using the ppp bicrystal. Here i briefly describe my problem. According to doc of Lammps, the essence of the “fix orient/fcc” command is to impose a crystal orientation-dependent driving force on atoms, and only atoms near boundaries suffer such force, then atoms near the upper, middle and low boundaries will move. While motion of atoms near the upper and low boundaries will effect the motion of atoms near the middle boundary, which is used to calculate the gb mobility, so I have to constrain atoms near these two boundaries to move. Here is my approach: in order to avoid the effect of the upper and low boundaries on mobility calculation, i set atoms near these two boundaries to be still by not imposing driving force on all these atoms. According to my understanding of periodic boundary, if boundary condition perpendicular to grain boundary is set to be ‘p’, then atoms near the upper and low boundaries should suffer driving force as atoms near the middle boundary do, i.e. the upper and low boundaries should move as the middle boundary does. So i want to know whether my approach goes against attribute of periodic boundary.
i have absolutely no idea what you are rambling about here.