Electrons and Hydrogen-Bond Connectivity in Liquid Water

The network connectivity in liquid water is revised in terms of electronic signatures of hydrogen bonds (HBs) instead of geometric criteria, in view of recent x-ray absorption studies. The analysis is based on ab initio molecular-dynamics simulations at ambient conditions. Even if instantaneous threadlike structures are observed in the electronic network, they continuously reshape in oscillations reminiscent of the $r$ and $t$ modes in ice ($\tau \sim 170\mathrm{fs}$). However, two water molecules initially joined by a HB remain effectively bound over many periods regardless of its electronic signature.