Using our recently developed platform for local number fluctuations with a special focus on the higher-order moments, we analyzed density fluctuations in ordered and disordered phases of water across temperatures.
Michael A. Klatt, Jaeuk Kim, Thomas E. Gartner III, and Salvatore Torquato, Local number fluctuations in ordered and disordered phases of water across temperatures: Higher-order moments and degrees of tetrahedrality, The Journal of Chemical Physics 160, 204502 (2024).
Some anomalies of water are well-know, for example, that ice floats on
water because the crystalline ice is less dense than the disordered
liquid. These commonly known anomalies are only part of a large set
of interrelated anomalies of water in its dynamic, structural, and
thermodynamic properties.
In this work we find another anomaly in the density fluctuations of
water. Therefore, we use a recently developed platform to systematically
study local fluctuations in the number of molecules with a focus on the
higher-order moments of the distribution of these fluctuations. We apply
it to a rich variety of simulated states of water, crystalline and
disordered, in equilibrium and quenched, and for a broad range of
temperatures (from 80 K to 1600 K). What we find is yet another type of
anomaly: simply speaking, an approximation of the distribution by a
(standard) Gaussian distribution works best close to ambient conditions.
This local optimum around room temperature is probably due to a
balancing of thermal fluctuations and the tretrahedrality of water since
we observe clear signatures of tetrahedrality in the higher-order
moments. This new type of anomaly can help further studies to reveal new
links between the already known structural, dynamic, and thermodynamic
anomalies.
Michael Andreas Klatt 