Electronic structure of InTe, SnAs and PbSb: Valence-skip compound or not?

• We calculated the electronic structure of InTe, SnAs and PbSb from first principles.
• Obtained tight-binding parameters of InTe are close to those of BaBiO3, which suggests that their electronic properties are also alike.
• InTe is favorable to emerge valence skip, while PbSb is not favorable for it. SnAs is between the two.
• Our findings well agree with the experimental results.

InTe, SnAs and PbSb formally have unusual valence states, In2+, Sn3+ and Pb3+. All of them have B1 crystal structure at some pressure range. They are candidates of the valence-skip compound, which may have negative effective Coulomb interaction Ueff < 0. Negative-U Hubbard model is known to show charge-density wave or superconductivity in some parameter region. In fact, SnAs becomes superconducting at ambient pressure. InTe has a kind of charge-density wave at ambient pressure, and it becomes superconducting at high pressure. We investigated their electronic structures by ab-initio calculations, and calculated the number of s-electrons at the cation site. We found that InTe is favorable to emerge valence skip, while PbSb is not favorable for valence skip. SnAs is between these two. These findings well agree with the experimental results.