부산대학교 도서관

The present study reports insight into electronic structure and stability of EuGe.sub.n (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 EuGe.sub.16 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 EuGe.sub.16 is from Ge.sub.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.sup.7 is responsible for the high magnetic moment of the EuGe.sub.16 cluster. Single-electron orbital analysis of the upper 34 electrons of EuGe.sub.16 with the sequence 2S.sup.21G.sup.162P.sup.42D.sup.22P.sup.22D.sup.8 can be split as 18[sigma] and 16[pi] electrons. These 18[sigma] electrons follow Hirsch's 2(n + 1).sup.2 rule for n = 2. The remaining 16[pi] electrons do not directly follow Hückel (4n + 2) [pi] rule. After splitting 16 electrons as 6[pi] + 10[pi] for n = 1 and 2, respectively, can follow Hückel'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 Hückel (4n + 2) [pi]-electron rule. Further, infrared and Raman spectra confirm that EuGe.sub.16 is a symmetric spherical shape with fewer vibrational modes than the other ground-state structures. Graphical Abstract
Author(s): Ravi Trivedi [sup.1], Antara Banerjee [sup.2], Debashis Bandyopadhyay [sup.3] Author Affiliations: (1) grid.418304.a, 0000 0001 0674 4228, High Pressure and Synchrotron Radiation Physics Division, Bhabha Atomic Research Centre, , [...]