Orient Command and Establishment of Periodic Structure

Dear all,

Now I am struggling in using command “orient” to build a periodic supercell system.

From the manual and mail list, I learned one should make sure the size of the simulation box coincident with the periodic size along the certain “oriented” direction, thus, the periodic system would be built.

And the periodic size should be integer multiple of lattice spacing. Is my understanding right?

If so, there seem to be some problems when I build a periodic supercell followed by this script.


------------------------ INITIALIZATION ----------------------------

units metal

dimension 3

boundary p p p

atom_style atomic

variable latparam equal 4.05

----------------------- ATOM DEFINITION ----------------------------

lattice fcc ${latparam}

lattice fcc ${latparam} orient x 1 1 2 orient y -1 -1 1 orient z 1 -1 0

region whole block 0 66.1362 0 70.1481 0 17.18268 units box

create_box 1 whole

create_atoms 1 region whole

Script end

As depicted by lammps.log file, the Lattice spacing in x,y,z = 6.61362 7.01481 5.72756 after the command lattice fcc ${latparam} orient x 1 1 2 orient y -1 -1 1 orient z 1 -1 0

Was inputted.

So I make sure the Size of the whole box keep to 66.1362, 70.1481,17.18268, respectively, which are also 10 times, 10 times and 3 times of the Lattice spacing in x,y,z.

But still, I can not get the periodic system. (Especially in x and y direction.)

Is there any way or method or any algorithm to get a periodic system?

Thank you in advance!


Li Li

It is not the spacing that matters but the correct periodic continuation and that depends on the angle.
If you tilt your lattice by 45 degrees you need 2 instances of the lattice in that direction to have compatible faces. If you tilt by 30 or 60 degrees, you need 3 and so on. The flatter and the more complex the lattice is tilted versus the box, the more replica you need.