  The application of newly developed first-principle modeling techniques to
liquid water deepens our understanding of the microscopic origins of its
unusual macroscopic properties and behaviour. Here, we review two novel ab
initio computational methods: second-generation Car-Parrinello molecular
dynamics and decomposition analysis based on absolutely localized molecular
orbitals. We show that these two methods in combination not only enable ab
initio molecular dynamics simulations on previously inaccessible time and
length scales, but also provide unprecedented insights into the nature of
hydrogen bonding between water molecules. We discuss recent applications of
these methods to water clusters and bulk water.
