Mössbauer studies of FeSn molecules isolated in rare-gas solids and SCF–Xα–scattered-wave molecular-orbital analyses of Sn2and 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 (FexSny; 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(3dFe, 5sSn)σ1(3dFe)σ2(4sFe 5pSn)σ2(4pFe,5pSn)π2.75(3dFe)δ2.25(3dFe)π1(5pSn)} 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.