Structure and thermodynamic properties of Li8Al3Si5

The equilibrium structure of the compound Li8Al3Si5 has been obtained via the minimization of the total energy within local spin density approximation (LSDA) based on density functional theory (DFT). The calculated lattice constant and bond length are in good agreement with available experimental values, and the phonon band structure is also described. In the meantime, the thermodynamic properties are investigated applying Debye model combining with the first principle theory in the quasi-harmonic approximation. The evaluated lattice constant and bulk modulus using this model both well agree with the values from ab intio and from the experiment. Our results demonstrate that this method can provide reliable predictions for the temperature and pressure dependence of these quantities, such as the equation of state, the bulk modulus, the Debye temperature, the heat capacity and the thermal expansion in detail.