Electronic structure and ionic diffusion of green battery cathode material: Mg2Mo6S8

• We report the crystal and electronic structure of Mg2Mo6S8.
• Mg2Mo6S8 possesses a triclinic geometry having a semiconducting feature.
• Mg ions diffuse through the channel between Mo6S8 blocks in [010] direction.
• The dynamical stability of Mg2Mo6S8 is confirmed by phonon dispersion.

We report ab-initio density functional theory calculations of crystal and electronic structure of Mg2Mo6S8, a candidate material to be used in rechargeable magnesium batteries, by employing hybrid exchange–correlation functionals. We find that Mg2Mo6S8 crystalizes in a triclinic geometry and it is a semiconductor with an indirect band gap. Ab-initio molecular dynamics shows that Mg ions present progressive diffusion starting at 200 K with a preferable path through the channel between Mo6S8 blocks along the [010] direction. The intercalation voltage of the system is also determined and the results show that the voltage evaluated by PBE and hybrid functionals likely implies the lower and the upper limit of the experimental value. Lastly, we confirm the dynamical stability of the crystal structure by the calculated phonon dispersion relation.