DFT studies on structural properties and electron density topologies of the iron selenides FemSen (1 ≤ m, n ≤ 4)

Abstract

We report the structural properties and electron density topologies of the iron selenides Fe_mSe_n (1 ≤ m, n ≤ 4) using DFT method. Structural studies reveal the Se atom leads to significant change in the geometries of the iron selenides. We confirm that the bond length between Fe atoms increase owing to the sequential addition of Se atom. Comparable stabilities were investigated based on the variation of averaged binding energies and selenium doping energy. The covalent property of the Fe–Se bond is increased as the coincident bond critical points (BCPs) showed smaller positive \(\nabla _{{\rho _{BCP}}}^2\) values than those of original FeSe molecule. Our results demonstrate that the ρ_Fe–Fe values keep in the order of 0.048–0.220 a.u. Almost all of the \(\nabla _{{\rho _{BCP}}}^2\) values are positive and consequently mean the closed-shell interactions are conserved in the iron selenides.