We conventionally think of liquids as disordered but dense ensembles of atoms or molecules chiefly characterized by their flow properties, for instance their viscosity. Nonetheless, a closer look to model liquids in experiments and computer simulations has revealed that, at low temperature and/or high pressure, systems that are globally disordered present non-trivial orientational and translational correlations at a local scale. I will discuss how these can be rationalised within an energy landscape picture [1] of the structure and relaxation of liquids, emphasising the role played by the number of metastable states or, better, its logarithm i.e. the configurational entropy [2], and hits relation with the flow properties, such as the viscosity. I will then discuss in detail a variety of cases where non-trivial local correlations emerge in disordered systems: I will start with colloidal spheres [3, 4], move to classical atomistic liquids [5] and conclude with recent results on a surprisingly complex liquid such as Gallium [6]. In this journey, we will invoke and describe several theoretical tools:the morphometric theory of liquids [7], geometric frustration of liquids [8] and structural-dynamical phase transitions [9].
[1] Stillinger. Energy Landscapes, Inherent Structures, and Condensed-Matter Phenomena. Princeton University Press, (2015).
[2] Berthier, Ozawa Scalliet, J. Chem. Phys. 150, 160902 (2019)
[3] Hallett, Turci, Royall, Nature Communications , 3272 (2018)9
[4] Robinson, Turci, Roth, Royall, Phys. Rev. Lett. , 068004 (2019)122
[5] Turci, Royall, Speck, Phys. Rev. X , 031028 (2017)7
[6] Drewitt, Turci, Lord,et al in preparation (2019)
[7] Robinson, Turci, Roth, Royall, (2019) arXiv:1908.03508
[8] Turci, Tarjus, Royall, Phys. Rev. Lett. 118, 215501, (2017)
[9] F Turci T Speck and CP Royall, Eur. Phys. J. E, 41: 54 (2018)
BIOGRAPHY : Francesco Turci obtained his PhD in Physics in 2012 at the Université de Montpellier (France) on a project on transport and kinetically constrained models. From 2012 to 2014 he worked as a Postdoctoral Fellow at the University of Luxembourg on crystallisation and nonequilibrium solid-liquid interfaces. Since 2014, he is Senior Postdoctoral Research Associate at the University of Bristol (UK), working on theory and numerical simulations for glass forming liquids, gels, crystals and active systems in close collaboration with experimentalists.