How does tetrahedral structure grow in liquid silicon upon supercooling?

We present an extensive set of isothermal-isobaric first-principles molecular-dynamics simulations of liquid silicon over a temperature range of 950-1700 K. We find that the tetrahedral order gradually grows upon cooling to similar to 1200 K, but that the growth accelerates significantly below similar to 1200 K. This growth process gives rise to anomalous changes in density and liquid structure upon supercooling. In particular, we find that the atomic coordination number remains constant to similar to 1200 K and then begins to decrease below similar to 1200 K, which resolves the existing controversy regarding liquid structure in the supercooled regime.