the antibonding-sister of ?

The crystalline and electronic structures of CaSi2 under high-pressure are very similar to those of MgB2. As CaSi2 has two more valence electrons than MgB2, the highest occupied σ band is bonding for MgB2 and antibonding in CaSi2. We investigated whether high-pressure CaSi2 superconductivity is similar to that in MgB2, with a large electron–phonon coupling between the E 2 g mode and the in-plane σ band of the Si sheets. Indeed, this electron–phonon coupling is important, but within the approximations of our calculations (Density Functional Theory, Frozen-Phonon, McMillan Formula), it would not be high enough to account for the superconductivity of high-pressure CaSi2 at T c ∼ 14 K .