The mechanics of charge-shift bonds: A perspective from the electronic stress tensor

The mechanism of charge-shift bonding is discussed from the perspective of the electronic stress tensor. In charge-shift bonds, the tensile mode of the stress tensor (attraction of electrons to the nuclei) is stronger, relative to the compressive modes (attraction of electrons toward the bond axis) than in conventional covalent bonds. Similar bonding indicators based on the eigenvalues of the tensor of second derivatives of the electron density and bond metallicity measures also correlate with charge-shift binding. These indicators seem preferable to the electron-density Laplacian and the local energy density because they can distinguish between weak covalent bonds and charge-shift bonds.