The charge flow CF model

The charge flow (CF) model, which is essentially a refinement of the FPC model, was introduced by Abbate et al. (1981). It consists of the FPC terms already described and new terms describing the contribution of the charge flow. 

Here c denotes the unit vector along the of equilibrium direction of the a bond and / the equilibrium length of that bond, is the vector which crosses . Lone pair electrons are not taken into account. 

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