QuantumATK Forum

QuantumATK => General Questions and Answers => Topic started by: sweta on April 26, 2013, 10:05

Title: doubt in selecting bond length
Post by: sweta on April 26, 2013, 10:05

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 ????

Title: Re: doubt in selecting bond length
Post by: Anders Blom on April 26, 2013, 11:28

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.

Title: Re: doubt in selecting bond length
Post by: sweta on April 27, 2013, 08:42

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???

Title: Re: doubt in selecting bond length
Post by: Anders Blom on April 27, 2013, 16:37

Quote from: sweta on April 27, 2013, 08:42

...
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.