Interaction pair | Molecule | B3LYP/6-31+G(d,p) | CCSD/6-31+G(d,p) |
---|
Eint(kcal/mol) | R(Ã…) | Eint-kcal/mol) | R(Ã…) |
---|
a π-π stack | C6H6-C6H6 | +0.100 | 7.874 | −1.883 | 4.262 |
b H-π | C6H5CH6-Imid | −2.444 | 3.616 | −5.897 | 3.324 |
c H-b | NMA-NMA | −5.827 | 2.186 | −6.023 | 2.022 |
Coordinate | Imid-Na+ | −38.045 | 2.267 | −36.788 | 2.317 |
d Cation-Ï€ | C6H6CH3-H3O+ | Eint(kcal/mol) | R(Ã…) | CPU time | Â |
B3LYP/6-31+G(d,p) |  | −17.791 | 2.781 | 1.08 hours |  |
CCSD/6-31+G(d,p) |  | −18.147 | 2.781 | 50 days |  |
CCSD(T) /6-31+G(d,p) |  | −18.872 | 2.781 | 86 days |  |
- a DFT method B3LYP/6-31+G(d,p) cannot yield attractive interaction energy for C6H6-C6H6 π-π stacking interaction, failing in describing the dispersion dominated π-π stacking interactions.
- b ‘H-π’ indicates the interaction between polar hydrogen atom with aromatic molecule in ‘T’ orientation, in which the dispersion energy contributes more than 50%. The energy difference between CCSD and DFT calculations is defined as the dispersion contribution.
- c ‘H-b’ indicates the common hydrogen bond interaction, which is the MO-coordinated and charge dominated interaction.
- d In the cation-Ï€ interactions the electrostatic interactions and MO orbital coordinate interactions make the main contributions, and the dispersion contribution is less than 10%.