What are delta energies?

The delta energy is an estimate of the surface energy of a cluster. The delta energy is defined as:

\[\Delta = \frac{E - NE_{coh}}{N^{2/3}}\]

where \(\Delta\) is the delta energy, \(E\) is the energy of the cluster, \(N\) is the number of atoms in the cluster, and \(E_{coh}\) is the cohesive energy of a crystal lattice of the same metal that the clusters contain (where \(E_{coh}\) is given in eV/atom). The \(N^{2/3}\) term is an estimate of the number of surface atoms that the cluster contains in a spherical cluster. The units of \(\Delta\) are eV/atom, or eV per estimate number of surface atoms.

See the article for more information about the delta energy: A. L. Garden, A. Pedersen, H. Jónsson, “Reassignment of ‘magic numbers’ of decahedral and FCC structural motifs”, Nanoscale, 10, 5124-5132 (2018), DOI: 10.1039/C7NR09440J