about calculating strain at the interface

[debjani]

While constructing an interface, how are the strains calculated in ATK? The standard method of (difference in lattice parameter/respective lattice parameter) does not result into the same value as the displayed strain during interface construction. For example, if I am constructing an interface of MoS2 4X4X1 with Au[111] 4X4X1, strain on Au, as calculated from lattice mismatch is (3.16-2.88)/2.88 ~ 9.7%. However, while constructing this interface, ATK shows a strain of 0.83%. Please explain.

[Petr Khomyakov]

You can choose to strain MoS2 or Au surface structures, or both equally.

Regarding 0.84% vs 9.7 % of strain, as far as I can see the problem is that you have selected a larger supercell (which is not the one corresponding to the original 4x4 in-plane unit cell) in the Interface Builder, as there are many possible ways of building the MoS2(0001)|Au(111) interface structure.  When choosing the 4x4 cell, I get strain of 9.35 %, in good agreement with your estimate. I have also found a structure with strain of 0.84%, but it does not correspond to the originally-built 4x4 cell.

[debjani]

Thank you so much for your reply! I could regain the strain ~8% after cleaving the Au[111] surface and choosing the right unit cell.