Mössbauer studies of FeSn molecules isolated in rare-gas solids and SCF–Xα–scattered-wave molecular-orbital analyses of Sn2 and FeSn diatomic molecules

Abstract

Iron–tin molecules were isolated in rare-gas solids and studied using both ⁵⁷Fe and ¹¹⁹Sn Mössbauer isotopes. Experiments at very dilute concentrations were performed to detect FeSn diatomic molecules. Larger clusters were identified by concentration dependence studies and Monte Carlo calculations. The ⁵⁷Fe and ¹¹⁹Sn isomer shifts (IS) for FeSn diatomic molecules suggest a covalent bonding between Fe and Sn atoms. Similar behaviour was observed for large iron–tin clusters (Fe_xSn_y; x, y 3). SCF–Xα–SW calculations were performed for Sn₂ and FeSn diatomic molecules. Sn₂ shows a ³∑_g ground state and gives a quadrupole splitting (QS) consistent with the experimentally measured value at an equilibrium distance of 2.75 Å. The most probable ground state for FeSn is a ⁷Δ{σ²(3d_Fe, 5s_Sn)σ¹(3d_Fe)σ²(4s_Fe 5p_Sn)σ²(4p_Fe,5p_Sn)π^2.75(3d_Fe)δ^2.25(3d_Fe)π¹(5p_Sn)} configuration which gives the QS values for iron and tin atoms in agreement with the experimentally measured values at an equilibrium distance of 2.5 Å.