doubt in selecting bond length

[sweta]

Hello all,

As we know there is a difference (relation) in the distance between metal electrode and anchoring atom and the adsorption height in fcc site. Therefore, i have a doubt in the article

Adsorption of benzene thiolate on the (111) surface of M (M=Pt, Ag, Cu) and the conductance of M/benzene dithiolate/M molecular junctions: a first-principles study,W.T. Geng, Jun Nara, Takahisa Ohno, Thin Solid Films 464–465 (2004) 379– 383

the bondlength reported in the fcc site is either the distance between metal electrode and anchoring atom or the adsorption height ?

[Anders Blom]

The commonly quoted value around 2.39 Å is for the bond distance (atom to atom) between the metal surface atoms and the sulphur atom, and this article also uses the term "bond length" which makes it clear what the value refers to.

[sweta]

Thank you Dr Blom for your prompt response.
According to relation
                            Au-S distance=[(adsorption height)^2+〖1/3(Au-Au distance)〗^2 ]^(1/2)

For commonly used Au-S bondlength=2.39 and adsorption height=1.71 as i discussed before in this forum, Au-Au bond must be 2.88 but the exp value of Au-Au bond is 2.472.

If i want to calculate adsorption height for Ag or Cu electrode for a given Ag-S or Cu-S bond, what value for Ag-Ag and Cu-Cu bond i should use either exp or anything else???

[Anders Blom]

...
the exp value of Au-Au bond is 2.472.
...

Taking the experimental lattice constant 4.078 Å you get the Au-Au bond length = 4.078/sqrt(2) = 2.88 Å as required.