s-p mixing in a one-dimensional tight-binding chain
= s-p mixing in a one-dimensional tight-binding chain
{title2=$H_{sp}(k)=2i\beta_{sp}\sin(ka)$}
Opposite <parity> of same-centre <s orbitals> and axial <p orbitals> makes their left and right nearest-neighbour <hopping integrals> opposite in sign. Their <Bloch wave> sum is consequently odd in wavevector and vanishes at the zone centre and boundary. Away from those points, <orbital hybridization> repels coupled levels and can produce an <avoided crossing>.