First-principles calculations of the electronic, optical properties and quantum capacitance of Mn doped Sc2CO2 monolayer under biaxial strain

The electronic structures and quantum capacitance of Mn atom doped Sc2CO2 under biaxial strain are investigated by first-principles calculations. The results indicate that pristine Sc2CO2 monolayer is nonmagnetic, while Mn doping makes the system have the magnetic character, which is mainly from Mn and C atoms neighboring to Mn atom. The total magnetic moment under strain ranges from 2.16 μB to 2.69 μB. The local magnetic moment of Mn atom under strains ranges from 2.59 μB to 4.33 μB, and the variation in local magnetic moment has the largest value of 1.84 μB. Spin-up band structures under strain exhibit the characteristic of the indirect semiconductor, and have the largest band gap of 0.3 eV at −2 % strain. The spin-down band structures under strain show the character of direct semiconductor and the largest band gap is 1.83 eV at 2 % strain. Sc2CO2-Mn under strains except +5 % are suitable for cathode material, while Sc2CO2-Mn with +5 % strain changes to cathode material in ionic/organic system. Effective mass, work function, and optical properties are further explored.