The influence of charge ordering in the microscopic structure of monohydroxy alcohols

Abstract

While radiation scattering data provides insight inside the microstructure of liquids, the Debye relation relating the scattering intensity $I(k)$ to the atom-atom structure factors $S_{ab}(k)$ shows that, ultimately, it is these individual structure correlation functions which contain the relevant information about the micro-structure. However, these quantities are not observables, except in few cases where one can invert the Debye relation in order to obtain the structure functions. In the majority of other cases, the need for model dependent computer simulations is unavoidable. The resulting calculations reveal that the scattering pre-peak is the result of cancellations between positive pre-peaks and negative anti-peaks contributions from the atom-atom structure factors. What of systems where this cancellation is such that it entirely suppresses the scattering pre-peak? One would be tempted to falsely conclude that there is no uderlying micro-heterogeneity. Hence, the structure functions appear as hidden variables, and it is important to understand the relation between their features and the micro-structure of the system. Through the computer simulation study of various mono-ols, ranging from methanol to 1-nonanol, as well as the branched octanols, we show how the features of the atom-atom pair correlation function $g_{ab}(r)$ affect that of the structure factors $S_{ab}(k)$, and reveal that the micro-structure is ultimately the result of the charge ordering between different atoms in the system.