The q = (3/8, 0, 1/2) instability in kagome CsV₃Sb₅ from first principles

The kagome metal CsV₃Sb₅ develops signatures of structural order at a high-symmetry-line k-point near k_R=(3/8, 0, 1/2) under pressure. In this talk, we present first-principles identification of this 3/8 (R) instability and discuss its evolution with pressure and doping. We also construct a phenomenological Landau theory to elucidate the competition between the R instability and the well-established L and M instabilities.