CCL:G: Calculating interaction energy/bond energy between atoms in mole:G

 Sent to CCL by: "Yuanhe  Li" []
 Counterpoise is a correction for BSSE error in (weak) intermolecular interaction
 energy. What you want is probably irrelevant to it.
 If you mean by cutting the 4 bonds:"1-4,5-28,3-8,11-17"
 splitting the molecule in to two (tetra-radical?) fragment, and you want the
 interaction between those (roughly equal to the sum of the bond energies). You
 can just calculate the two fragments A, B, the molecule AB; get the difference
 of electronic energy. This is a (very) strong interaction, thus no counterpoise
 is required. However, I can't see why this is meaningful, and the fragment
 electronic structure might be tricky.
 If you mean you want the bond energy for each of the 4 bonds, be aware that the
 bond energy of a bond inside a ring is ambiguous. You have the liberty to design
 reasonable processes to represent it, like rotating one side of the ring away
 > from the bonding position, then calculate the singlet biradical. Also one
 try to cancel any artificial interaction during the process like steric
 repulsion. Or you can calculate the Laplacian bond order, which is well
 correlated with bond energy in organic systems. (Laplacian bond order cannot be
 calculated by Gaussian, try Multiwfn:
 Sent to CCL by: "Nikhil  Maroli" [scinikhil[#]]
 Dear all,
 im new to gaussian,
 i wanted to calculate the interaction energy between the atoms in the
 molecules (image :
 I know I can use counterpoise method by making it two fragments ,but how it
 is possible for finding interaction energy between the 1-4,5-28,3-8,11-17.
 how I make fragments?
 Any suggestion will be helpful