Structural, electronic, and magnetic properties of FeSi: hybrid functionals and non-local exchange

The structural, electronic, and magnetic properties of FeSi are investigated by first-principles all-electron density functional calculations. The interplay between non-local exchange and correlations is studied by comparing results obtained with standard density functionals, the hybrid functional B3LYP and the Hartree-Fock ansatz. The calculations are performed using a local basis set. For the standard functionals, previous theoretical results for the non-magnetic semiconducting ground state are well reproduced. With the hybrid functional B3LYP, a magnetic metallic solution is found in addition to the non-magnetic low-energy semiconducting one. The influence of the non-local exchange is also reflected in the increased value of the indirect gap which separates the valence and conduction bands.