how to choose AU-S bond length in molecular device

[sweta]

Hello all,

In tutorial
http://www.quantumwise.com/publications/tutorials/mini-tutorials/76-simple-way-to-build-a-molecular-device-structure

you select adsorption height=1.71 Å which will give a distance Au-S=2.39 Å.
what is the relation between these two values??
what values of adsorption height I should choose that will give Au-S bond length= 2.33, 2.76, 3.06, 3.67, 4.29
Kindly help!

[zh]

In that case, the molecule may be adsorbed on the hollow site of Au surface, rather than the top site of Au surface. So the adsorption height is not equal to the distance of Au-S. If the molecule is adsorbed on the hollow site of Au(111) surface (used as electrode), the relationship between the Au-S distance and the adsorption height  will be:
 the Au-S distance = sqrt[ (the adsorption height)^2 +  1/3 (the Au-Au distance in Au(111) surface)^2 ]

For a given adsorption height, the Au-S distance can be measured by picking up Au and S atoms.

[sweta]

Thanx you so much sir.

Two more things:
1. how we can measure conductance in terms of G0 and then sulphur charge for two probe system
2. how we can make OPE geometry by creating bond between two carbon atoms in ATK-VNL.