Insight into stabilities and magnetism of EuGen (n=1-20) nanoclusters: an assessment of electronic aromaticity

The present study reports insight into electronic structure and stability of EuGen (n = 1-20) nanoclusters under the framework of density functional theory within the generalized gradient approximation. To understand the stabilities and the magnetic behavior of endohedral nanoclusters with the structural growth, different parameters, such as, average binding energies, fragmentation energies, energy difference between highest occupied and lowest unoccupied molecular orbitals, vertical ionization potential and adiabatic ionization potential are studied. It is found that EuGe16 in octet spin state is the most stable both thermodynamically and chemically. Furthermore, the study of natural bond orbital and electron localization function indicates that the charge transfer in global ground state EuGe16 is from Ge-n cage to Eu atom. Calculated density of states and projected density of states show the hybridization between 5d, 6 s, and 6p orbitals are mainly responsible for the stability, and 4f(7) is responsible for the high magnetic moment of the EuGe16 cluster. Single-electron orbital analysis of the upper 34 electrons of EuGe16 with the sequence 2S(2)1G(16)2P(4)2D(2)2P(2)2D(8) can be split as 18 sigma and 16 pi electrons. These 18 sigma electrons follow Hirsch's 2(n + 1)(2) rule for n = 2. The remaining 16 pi electrons do not directly follow Huckel (4n + 2) pi rule. After splitting 16 electrons as 6 pi + 10 pi for n = 1 and 2, respectively, can follow Huckel's rule. So, by applying the mixed pi-sigma mixed electron counting rule, the stability of the cluster can be explained. Further, calculated nucleus-independent chemical shift also supports the existence of the Huckel (4n + 2) pi-electron rule. Further, infrared and Raman spectra confirm that EuGe(16 )is a symmetric spherical shape with fewer vibrational modes than the other ground-state structures. [GRAPHICS] .

Automated summary

This study investigates the electronic structure and stability of EuGen nanoclusters using density functional theory. The results show that EuGe16 in the octet spin state is the most stable and exhibits high magnetic moment. The study also analyzes various parameters to understand the stability and magnetic behavior of the nanoclusters.