First-principles investigation of mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 phases

The mechanical, thermodynamic and electronic properties of FeSn5 and CoSn5 intermetallic phases at zero pressure have been systemically investigated by first-principles calculations using ultrasoft pseudopotential and generalized gradient approximation (GGA). The equilibrium lattice constants of FeSn5 and CoSn5 at zero pressure are in good agreement with the available experimental values. Thermodynamic and mechanical properties of FeSn5 and CoSn5 are predicted by calculating formation enthalpy, phonon density of states and elastic constants, respectively. Formation enthalpies calculation indicates that FeSn5 and CoSn5 are energetically unfavorable compare to FeSn2 and CoSn2. This may be the partial reason why FeSn5 and CoSn5 were hidden in the Fe/Co-Sn phase diagrams previously. FeSn5 and CoSn5 exhibit opposite relative incompressible behavior along a-axis and c-axis. Our results reveal that both FeSn5 and CoSn5 are mechanically and dynamically stable at 0 GPa. The quasiharmonic model is employed to calculate the temperature dependence of specific heat at constant volume. In addition, the electron density of states and electron density difference are calculated to disclose the underlying electronic structure. (C) 2015 Published by Elsevier B.V.