High-density liquid (HDL) adsorption at the supercooled water/vapor interface and its possible relation to the second surface tension inflection point

We investigate the properties of water along the liquid/vapor coexistence line in the supercooled regime down to the no-man’s land. Extensive molecular dynamics simulations of the TIP4P/2005 liquid/vapor interface in the range 198 – 348 K allow us to locate the second surface tension inflection point with high accuracy at 283$\pm$5 K, close to the temperature of maximum density (TMD). This temperature also coincides with the appearance of a density anomaly at the interface known as the apophysis. We relate the emergence of the apophysis to the observation of HDL water adsorption in the proximity of the liquid/vapor interface.