where \(\alpha\) is the index of an atom, \(\mathbf{R}_{\alpha}\) is the position of the atom, and \(Z_{\alpha}\) is the nuclear charge of the atom. The first term is the direct contribution to the total ESP from the monomers, the second term is a two-body correction from the dimers, and the third term is the ESP due to the atomic nuclei. The more detailed information about this equation can be found in the previous paper.33
The pESP can be introduced similarly to the pEDN, i.e.,