I am trying to understand the physical meaning of Wiberg bond indices, how does the value of WBI explain the interaction between any atoms? For example, I have two Ag atoms in one of my structure and WBI between them is 0.8067. Does it mean that there is a bond between them? I want to understand the significance of WBI. Please let me know if any review or paper is available.
There are different ways of understanding or interpreting Wiberg index. In my personal opinion, it is best to be understood as "the average number of electron pairs shared by the two atoms". For example, if the index between two atoms is close to 1.0, it can be interpreted as there is approximately one pair of electrons shared between them.
More details: In J. Phys. Chem. A, 109, 9904 (2005) the authors nicely elucidated the underlying relationship between AIM delocalization index and Mayer bond order, namely the Mayer bond order essentially is delocalization index (DI) between two atoms in Hilbert-space. The DI is a quantitative measure of number of electrons shared between two subspaces. Though the ideas of Mayer bond order and Wiberg index (also known as Wiberg bond order) are different, formally the very old Wiberg index proposed in 1968 can be viewed as a simplified form of Mayer bond order under orthonomal basis functions.
In your case, since 0.8067 is large, there should be prominent electron sharing between the two atoms, in other words, the two Ag atoms have evident covalent interaction.
The Wiberg bond order is one of many approaches to quantify the bond orders between atoms:
https://docs.eyesopen.com/toolkits/python/quacpactk/bondordertheory.html
So, formally, in the Wiberg approach your Ag atoms are somewhat bound together. However, I would not use Wiberg bonds as the sole origin of a bond order statement. A NBO (natural bond order) analysis or a simple Mulliken population should give quantities in the same order of magnitude if it should be meaningful; that should not be too much work for your computer.
If you want to get more sophisticated you could also try Bader's AIM (atoms in molecules) approach, but of course only if your package has that implemented.
Dear rajeev chand Nishad,
I suggest you to take a look at Multiwfn program and manual, numerous informations could be found.
http://sobereva.com/multiwfn/Multiwfn_manual.html
There are different ways of understanding or interpreting Wiberg index. In my personal opinion, it is best to be understood as "the average number of electron pairs shared by the two atoms". For example, if the index between two atoms is close to 1.0, it can be interpreted as there is approximately one pair of electrons shared between them.
More details: In J. Phys. Chem. A, 109, 9904 (2005) the authors nicely elucidated the underlying relationship between AIM delocalization index and Mayer bond order, namely the Mayer bond order essentially is delocalization index (DI) between two atoms in Hilbert-space. The DI is a quantitative measure of number of electrons shared between two subspaces. Though the ideas of Mayer bond order and Wiberg index (also known as Wiberg bond order) are different, formally the very old Wiberg index proposed in 1968 can be viewed as a simplified form of Mayer bond order under orthonomal basis functions.
In your case, since 0.8067 is large, there should be prominent electron sharing between the two atoms, in other words, the two Ag atoms have evident covalent interaction.
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