MCSQS Clusters & using a modified supercell

Alloy Theoretic Automated Toolkit (ATAT)
1

Hi Axel, or anyone who can respond to this.

I have currently a few configurations of a 128 atom supercell, Ga_64 As(1-x) Bi(x). Now, I want to replace some of the Gallium atoms with another element. But keep the configurations of Arsenic and Bismuth the same. This is so I can see what contributions adding in the new element does to my band gap energy.

From what I understand, there is no unit cell due to this (I’ve tried using the unit cell reduce command, it doesn’t give me one). Now the problem, when I use the same cluster commands from my 2 atom unit cell that generated the 128 atom supercell, there is a SIGNIFICANT difference in cluster numbers ( 9 vs 100s).

Is this due to generating the clusters on a unit cell vs the supercell? Is it equivalent if I run the same corrdump on the ‘reduced’ supercell that can’t be reduced? Is the time similar?

2

This due to a lowering of the symmetry of system. This can be due to super cells that cannot be reduced but also just if the symmetry is lower.