The only proper way to do it ab initio is to calculate the energy (E) for various internuclear distances (R) and then to approximate the equilibrium bond length by choosing the distance which has the lowest energy, or by fitting the E (R) points to something like a Morse potential (which is decent for short-distances), Lennard-Jones potential (which is decent for large distances), or the one ...
5 If your desire is to get the best bond length from that website, then I would begin by looking for the largest basis set (in this case it's aug-cc-pVQZ) and the method that is expected to recover the most correlation energy (in this case it's CCSD (T)=FULL), so the CCSD (T)=FULL/aug-cc-pVQZ bond length of 1.540 Å is a good starting point.
For very simple systems and tasks, such as optimizing the bond length of a diatomic molecule, it is straightforward to parameterize the geometry in terms of a single interatomic distance, and do multiple SCFs on your own at different interatomic distances to get a simple two-dimensional energy-interatomic distance plot to visualize the ...
Laplacian Bond Order This method is an extension of the QTAIM (Quantum Theory of Atoms In Molecules) concept of using the Laplacian of the electron density $\nabla^2\rho$ to characterize bonding. Standard QTAIM just uses the value of $\nabla^2\rho$ at bond critical points (minimum electron density along the bond, max along orthogonal directions), but these values are unintuitive and often don ...
What are the types of bond orders? - Matter Modeling Stack Exchange
If you know the bond lengths of few such compounds, you can derive a very accurate linear correlation between the bond length and the frequency. So while you can't directly predict bond lengths from IR alone, you can likely develop a correlation between a particular IR frequency and bond length for a series of related compounds.