Table 5 Important molecular descriptors derived from DFT and molecular dynamics simulations (Obot et al. 2013)
Descriptors | Explanation |
|---|---|
Global quantum chemical descriptors | |
E HOMO | Energy of the highest occupied molecular orbital |
E LUMO | Energy of the lowest unoccupied molecular orbital |
IP(≈‐ E HOMO) | Ionization potential: removing an electron from a molecular system X (X→X+ + e−) |
EA(≈‐ E LUMO) | Electron affinity: attaching an additional electron to a molecular system X (X + e−→X−) |
\( \mu ={\left(\frac{\delta E}{\delta N}\right)}_v \) | Chemical potential, defined as the change in electronic energy E upon change in total number of electrons N |
χ = − μ ≈ − 1/2(E HOMO + E LUMO) | Absolute electronegativity |
\( \eta =-{\left(\frac{\delta \mu }{\delta N}\right)}_v\approx -\left({E}_{\mathrm{HOMO}}-{E}_{\mathrm{LUMO}}\right) \) | Molecular hardness, defined as the change in chemical potential μ upon change in total number of electrons N |
\( S=\frac{1}{2\eta } \) | Molecular softness |
Α | Molecular polarizability; note that molecules arrange themselves towards a state of minimum polarizability and maximum hardness |
\( \omega =\frac{\mu^2}{2\eta }=\frac{\chi^2}{2\eta }. \) | Electrophilicity index |
Charge distribution | |
QA(r) | Net atomic charges (at atom r) |
E interaction = E total − (E surface + E inhibitor) | Where E total is the total energy of the metal surface and inhibitor, E surface is the metal surface energy and E inhibitor is the energy of inhibitor molecule from plant extract |