Hello Majid Moghaddam, as for the voronoi tessellation you can control the size by the postioning and Distribution of the grain cores which are generated first. I distribute a simple voronoi FORTRAN code through my researchgate paper list (look for data sets) which you can download and manipulate by yourself until you are satisfied with the Distribution of the grain cores and the generated grain structure. However you Need to get a public Domain ftn Compiler to run the program and to generate the structure. But at the end you should be able to generate a read-in file for LAMMPS by yourself. Good luck!

Thank you Dr. Rentsch for your help! I think that's just what I need!

There are links in the site below for generating crystalline material -

https://kedharnath1992.wordpress.com/category/grain-boundary/

Dear Majid Moghaddam,

We have developed a open-source code called NanoSCULPT which can generate atomistic structures from arbitrary 3d enclosed volumes. See the corresponding paper for more details:

A. Prakash, M. Hummel, S. Schmauder and E. Bitzek [2015], NanoSCULPT: A methodology for generating complex realistic configurations for atomistic simulations, MethodsX, 3, 219-230

http://dx.doi.org/10.1016/j.mex.2016.03.002

The code can be downloaded from the official repository:

https://bitbucket.org/arunpksh/nanosculpt/

We also provide some examples, one of which is in fact generation of Voronoi tessellated microstructures. Have alook into example 2 on this page

https://bitbucket.org/arunpksh/nanosculpt/wiki/Examples

Please refer to the Wiki of the repository on further details regarding licensing, citing NanoSCULPT etc.

 You can do that with code Atomsk. You may get it from http://atomsk.univ-lille1.fr/

Dear Moghaddam, 

You can create polycrystals with VORONORIZE tool, which is a part of a AtomEye utilities.  See the following link for more details. 

http://li.mit.edu/A/Graphics/A/utils.html

In the following paper, this tool has been used to create a polycrystal

https://link.springer.com/article/10.1007/s12666-015-0823-2

Article Fatigue Deformation of Polycrystalline Cu Using Molecular Dy...

ِDear Arun,

I'm familiar with "nanoSCULPT". like you said, it exacly does what I asked for.

I managed to compile and run it on linux ubuntu, but couldn't get the appropriate outputs! I guess I'm missing something!

should I generate a separate parameter file for each grain?

Dear Kedharnath,

your information was very helpful! I was looking for the GTA matlab codes and thanks to you I found them!

Dear Amlan,

Thank you! it worked for me! and it was very easy to use!

Dear G. Sainath,

Thank you for your answer. I red your article. you're right. The AtomEye seems to do the job, but I haven't tried it yet. though I used the Atomeye to visualize the structure generated by Atomsk.

Dear Majid,

yes, you need separate parameter files for each grain. After all, the parameters, at least the orientation, change from grain to grain.

What outputs are you referring to? could you provide more details.