Herein, the charge constraints for the force-field basins in molecular systems are formulated together with the governing relations for the fluxes of the electronic force fields through the boundaries of the atomic and force-field basins, \({\Omega }_{S}\) and \({\Omega }_{P}\) , defined by the electron density gradient \(\nabla \rho(\mathbf{r})\) and the conservative total static force field \(\mathcal{F}(\mathbf{r})\) , respectively. A chemically meaningful interpretation of the electron occupancy of the \({\Omega }_{P}\) basins is provided in terms of the exchange charge. It is demonstrated that the emergence of the negative exchange charge density, \({q}_{x}(\mathbf{r})=\nabla \cdot {\mathbf{F}}_{x}(\mathbf{r})/(4\pi)\) , characterizes the “exclusion” effect arising from the condensation of fermionic electrons into electron pairs. Furthermore, the electrostatic-field and total-static-field fluxes through the interatomic surface are interpreted to be induced by the difference in actual electronegativity between the chemically bonded atoms. This study advances an exploration of the subatomic structure of the diborane molecule by employing the above formulations in conjunction with recently developed exchange-force-derived chemical structure descriptors. It is revealed that the hydrogen exchange-force-field basins \({\Omega }_{X}\) —each containing a hydrogen nucleus yet governed by a nonnuclear attractor—encompass the internuclear binding regions associated with the highly polar B–H and B– \(\mu\) -H covalent bonds. When considering the conservative exchange force field \(\mathbf{F}_{x}(\mathbf{r})\) , both the nonnuclear attractors of the \({\Omega }_{X}\) basins of the bridging hydrogen ( \(\mu\) -H) sites are directly connected by two gradient trajectories, which originate at the line-type saddle equilibrium point situated at the geometric center of the B2 \(\mu\) -H2 rhombus. Notably, nearly all of negative \(q_x(\mathbf{r})\) , within the valence shell is confined to the hydrogen \({\Omega }_{X}\) and \({\Omega }_{S}\) basins. Specifically, \(q_x(\mathbf{r})\) assumes a dumbbell-shaped negative distribution that spans the \(\mu\) -H nuclei, thereby indicating the condensation of electron-pair density among them. By contrast, the hydrogen \({\Omega }_{P}\) basins avoid capturing an excessive portion of negatively valued \(q_x(\mathbf{r})\) in accordance with the corresponding charge constraint imposed on \({\Omega }_{P}\) . Furthermore, the negative scalar component of \(\mathbf{F}_{x}(\mathbf{r})\) , contributing to \(\mathcal{F}(\mathbf{r})\) , coupled with the positive scalar component of \(\mathbf{F}_{x}(\mathbf{r})\) , contributing to the interelectron interaction force \(\mathbf{F}_{\text{ee}}(\mathbf{r})\) —both observed along the perimeter and within the rhombic B2 \(\mu\) -H2 framework—elucidates the mechanism of the Fermi electron correlation that consolidates these four atoms into the unified B2 \(\mu\) -H2 assembly and sustains their cohesion within the diborane molecule.
