Fig. 2: Bandstructure of Ta2NiSe5 and Ta2NiS5. | npj Computational Materials

Fig. 2: Bandstructure of Ta2NiSe5 and Ta2NiS5.

From: Common microscopic origin of the phase transitions in Ta2NiS5 and the excitonic insulator candidate Ta2NiSe5

Fig. 2

Band structure of TNSe and TNS for the orthorhombic and monoclinic phase. For all the investigated exchange correlation functionals, we obtain a semimetallic groundstate for the high-temperature phase of TNSe. Only after the structural transition to the monoclinic geometry, a bandgap of between 40 and 183 meV opens. In TNS, already the orthorhombic phase exhibits a positive bandgap for the modified Becke–Johnson and HSE03 functional, which increases during the structural transition to the monoclinic phase. Therefore, the metal-to-insulator transition observed in TNSe is lacking for TNS. In all plots, the Fermi energy is set to 0 eV. The self-consistently calculated c-value for TNSe is c = 1.25 and c = 1.26 for TNS in both geometries.

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