engleski

Spatial and temporal universalities of hydrogen bonding in associative liquids

Formation of labile aggregates (clusters) in hydrogen bonding liquids, such as water or alcohols, is well-known phenomenon. Lifetime of such aggregates is important microscopic parameter and can be calculated in computer simulations. Statistical nature of these clusters suggests that their lifetime distribution should be broad Gaussian-like function of time, with a single maximum representing the mean lifetime of these structures. This distribution would be weakly dependent on bonding criteria, such as the distance or angle, while the long time part is known to have some power law dependence. Surprisingly, lifetime distributions of hydrogen bonds in all liquids studied herein, namely water and alcohols, show three specific lifetimes in the time range 0 –0.5 ps. The dominant lifetime, which is attributed to hydrogen bonded pairs, depends strongly on the bonding distance criterion. This mode is absent in simple, non-associative liquids. The secondary and tertiary lifetimes are related to clusters and are nearly independent on the bonding criterion. Secondary mode is present also in lifetime distributions related to simple liquids, unlike the third mode which is absent in this case. This poses the question of the origin of the third lifetime. The study of alcohols reveals that the appearance of the third lifetime is related with the topology of H-bonded clusters. Furthermore, it is shown that the presence of alkyl tails may strongly influence the hydrogen bonding process in these liquids and, consequently, the overall shape of lifetime distribution of hydrogen bonds. Finally, this work displays the universal hierarchy of hydrogen bonding lifetimes with a timescale regularity across different types of hydrogen bonding liquids.

hydrogen bond ; associative liquids ; labile aggregates ; spatial and temporal universalities ; histogram of hydrogen bonding lifetimes ;

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