Spin-potential in density functional theory framework

Spin-potential in density functional theory framework 

To describe the chemical reactivity in the context of DFT, there are several global and local quantities useful to understand the charge transfer in a chemical reaction, the attack sites in a molecule, the chemical stability of a system, etc. In particular, there are processes where the spin number changes with a fixed number of electrons such processes demand the SP-DFT version [27,32]. In this approach, some natural variables are the number of electrons, N, and the spin number, Ns. The total energy changes, estimated by a Taylor series to the first order, are 

in systems where the multiplicity changes because there are electronic transitions, Equation (3) is suitable. 

For such a process, Galvan et al. [32] wrote the spin potential as 

The computation of the electronic structure for each Rc is by using the KS approach with a code designed to use Dirichlet boundary conditions. In this work, we use the Perdew and Wang exchange-correlation functional [33] within the local density approximation [34], Details about this code can be found in Ref. [9] and some applications are in Refs. [35-37], 

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