In their article, Petar Grujić and Nenad Simonović emphasize the value of the classical description of atoms in yielding simplicity, conceptual clarity, and analytical treatments of complex problems involving various atomic interactions. Quantum mechanics can often yield more accurate results, but at the expense of clarity, simplicity, and sophistication. A similar situation exists with our classical treatment1,2 of the work function of metals and the original quantum mechanical treatment by Eugene Wigner and John Bardeen.3
Consider the correspondence between the ionization potential of free, gaseous atoms and the work function of solid metals. Both are really ionization energies, only applied to different entities (atoms and solids) and artificially given different names. But both can be defined generically as the energy required to remove from the entity the most loosely bound electron(s) to infinity at rest, as Niels Bohr rigorously did for atoms.
The conceptual clarity offered by classical methods can yield comparatively easy extensions to more complex situations. For example, a generic dependence of the ionization energy on a solid’s size (particularly in the case of small particles) has been established and subsequently confirmed by experiments.4,5
Thus, consistent with the concepts put forward by Grujić and Simonović, simple classical concepts are also useful and valuable to treat complex phenomena such as the work function of metals and insulators, particle charging, triboelectric charge exchange, and so forth.
