Charge transfer contribution, SIBFA

Charge Transfer Charge transfer becomes important where metal-ligand bonds exhibit some degree of covalent character. Electron density from the bound ligands can be transferred to the central metal cation M, and back donation to or from the d-orbitals of transition metals can provide an additional energetic contribution. Charge transfer in SIBFA is based on the expression [53-55]... 

The SIBFA model [25, 26] (sum of interactions between fragments ab initio computed) obtains the energy of a system as the contribution of electrostatic multipolar, short-range repulsion, polarization, charge transfer and dispersion. 

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