[lammps-users] about periodic boundary condition

Hello,

I am doing MD simulation of void growth in aluminium single srystal. I am using periodic boundary condition, my question is that as lammps execute the command line by line. So, when i use periodic boundary condition to define my simulation box and then define the void region, then does lammps do periodic boundary to only the simulation box or also to the void. Below is the code for my structure. Is the definition of void structure is correct. Thanks in advance.

INITIALIZATION

units metal

dimension 3

boundary p p p

atom_style atomic

It will be for both. If you want to imagine, think of your system as infinite (if you include images) system of Al foam, where the voids are spaced at the distance same as your box dimensions in cubic(oidal) fashion.

So, if i want to include only one void in the center in my simulation, how should i proceed. Which boundary should i use. Moreover, i am using fix npt and fix deform, and lammps boundary command is like this…

A periodic dimension can change in size due to constant pressure boundary conditions or box deformation (see the fix npt and fix deform commands). The p style must be applied to both faces of a dimension.

-Mehul

One option is to great huge box so that one void don’t effectively see other void

I'm not sure what you are asking, but perhaps this line from the
region doc page is relevant:

IMPORTANT NOTE: Regions in LAMMPS do not get wrapped across periodic
boundaries, as specified by the boundary command. For example, a
spherical region that is defined so that it overlaps a periodic
boundary is not treated as 2 half-spheres, one on either side of the
simulation box.

Steve

In my simulation i am varying the size of void from 10 angstrom to 100 angstrom in step of 10 angstrom. I have kept my simulation box constant to 240 angstrom. Now, i think i have to keep volume fraction constant and vary the void size. Moreover, what is the calculation or how i will come to know whether one void is affecting the nearby void or not. What size of simulation or volume fraction will be good in my simulation.

-Mehul

Moreover, what is the calculation or how i will come to know
whether one void is affecting the nearby void or not. What size of
simulation or volume fraction will be good in my simulation.

These are questions you have to answer yourself. You could
try running multiple simulations with periodic boxes of different
sizes, each with a single void, and see how big the box needs
to be before your answers don't change.

Steve