Numerical studies of crystallization and vitrification: a novel and general method applied to water and B2O3

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(Institution)
Abstract
10-051 guillaume pierre jean ferlat ferlat, g.p.(Sorbonne Université); Under which circumstances will a system crystallize or vitrify remains a genuine and fascinating question. Although atomistic simulations are a priori natural tools for exploring the structure and energetics of liquids, the observation of nucleation phenomena remains in most cases extremely challenging because of the limited timescale affordable in such simulations as compared to the time required for crystals nuclei to form. Thus, nucleation has only been observed numerically in specific systems (very poor glass-formers) and/or by using seeding techniques and/or simplified force-fields. However, a general and transferable method, that would reveal the atomistic mechanism and the energetics of transformations has been lacking. Here, we present results obtained from a novel method which combines enhanced sampling techniques (metadynamics) and a topological metric, capturing changes in the topology of the interatomic network. Using water as a benchmark and challenging case, we are able to systematically track transitions among liquid, amorphous and crystalline forms throughout the whole phase diagram [1], including the nucleation of crystals above and below the melting point. We will then address the case of B2O3, arguably one of the best glass-former and notoriously known for its crystallization anomaly (abnormal reluctance to crystallize at ambient pressure) [2, 3]. 

[1] Navigating at will on the water phase-diagram, S. Pipolo, M. Salanne, G. Ferlat, S. Klotz, A.M. Saitta, F. Pietrucci. Phys. Rev. Lett., 119, 245701 (2017).  
[2] Rings in network glasses: the B2O3 case. G. Ferlat, in "Frontiers and challenges in molecular dynamics simulations of structurally disordered materials", Eds: C. Massobrio, J. Du, P. S. Salmon, M. Bernasconi, Springer (2015). 
[3] Hidden polymorphs drive vitrification in B2O3, G. Ferlat, A.P. Seitsonen, M. Lazzeri, F. Mauri, Nature Mat. 11, 925 (2012).
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