Confinement-induced orbital breathing, fusion, fission and re-ordering in semifilled shell atoms

Alternate contraction and drastic expansion, i.e., 'breathing' of electronic subshells, the effects of the fusion of two subshells into one subshell and its subsequent fission (splitting) into the original subshells, as well as multiple alteration of the order of subshells in confined semifilled shell atoms with a progressively narrowing confinement are theoretically discovered. The confinement is represented by a repulsive penetrable spherical potential of an inner radius r0. The effects are exemplified by calculated data for confined semifilled shell atoms from the second, third and fourth rows of Mendeleev's table-Li, N, P and Cr atoms with semifilled 2s1, 2p3, 3p3 and 3d5 subshells, respectively-for the completeness of the study. The underlying physics behind the discovered effects is explained.