what does "stacking fault" mean ?

[fangyongxinxi]

I make a two probe configuration as below (attachment 1), the details are: Au(1 1 1), surface vector is 4*4, left and right layers are both 3.
When setting Layers with 2, it shows "stacking fault , Second order matrix element will be ignored ", when setting layers with 3, it shows " Second order matrix elements will be ignored "
My question are: what does stacking fault mean, and this configuration with 2 layers is ok ?
                        I noticed that the structure detail of two Probe is different with 2 and 3 layers (attachment 2 ), why? Any rules should be notice when setting the TwoProbe configuration ?

[fangyongxinxi]

problem solved .The reason is the Au( 1 1 1) sruface is stacked as ABCABC, so the surface layers must be 3n.

[zh]

It is good to hear that you solve it by yourself.

The surface layers should be continuously matched with the atomic layers in electrodes. As you said, the stacking sequence of atomic layers in Au(111) is ABCABC..., so, if the atomic layers in electrode are just three layers with ABC, the atomic layers in surface layer may be chosen as AB, ABC or ABCA and etc. On other hand, if the atomic layers in electrodes are characterized as BCA, the atomic layers in surface layer is required to be BC, BCA, BCAB and etc.