Surface half metallicity and thermodynamic stability of 001-plane Ti2XSi (X=Mn, Co) Heusler alloys (HAs): A DFT approach

We report the surface stability and surface half-metallicity of Ti2XSi (X=Mn/Co) [001] slab with natural TiSi and TiX(X=Mn/Co) terminals from the first principles calculation. We started our calculation from the bulk optimization followed by the electronic and magnetic properties by adopting GGA exchange correlation for treating all electrons interaction. We have also analyzed the surface stability by calculating the surface energies as a function of constituents chemical potentials within the framework of ab-initio thermodynamics. Within the allowed chemical potentials range, TiSi(Ti2MnSi) terminated surface found to be the most energetically favorable thin film while the TiX terminated surfaces show strong molecular attraction. The bulk half metallicity is preserved in TiSi(Ti2MnSi) terminated surface with 100% spin polarization while the other terminal surfaces are metallic. The results of atomic site partial magnetic moments in the surface states along with their corresponding values in the bulk structure are also presented.