Structure of defective crystals and glasses

As for most real-world materials found in Nature, defective crystals and glasses lack the regularity of perfectly organised crystals while still possessing some short- or medium-range structural order. Their properties have therefore to be established from ensembles of microscopic local structures (rather than from periodic ordering). In this respect, atomistic simulations (such as molecular dynamics) offer a comprehensive framework enabling the identification of stable configurations and the quantitative determination of related spectroscopic, thermodynamic and dynamical properties.

Among the investigated crystals, we focus on the incorporation of chemical impurities in minerals offering new ways to better understand the atomic-scale machinery controlling geochemical or geophysical processes of global importance.

In glasses (i.e. non-crystalline solids obtained from the rapid cooling of liquids), we aim to establish the structural similarities with either the parent liquid or the underlying crystalline phases. We are in particular motivated by the existence of polyamorphic transitions (e.g. under pressure), i.e. transformations between distinct glassy states, in a way which recalls the transformations between polymorphic crystals.

Selected publications:

E. Balan, M. Blanchard, M. Lazzeri, J. Ingrin, Theoretical Raman spectrum and anharmonicity of tetrahedral OH defects in hydrous forsterite, European Journal of Mineralogy 29, 201-212 (2017)  

C. Crépisson, M. Blanchard, M. Lazzeri, E. Balan, C. Sanloup, New constraints on Xe incorporation mechanisms in olivine from first-principles calculations, Geochimica et Cosmochimica Acta, in press (2017)

E. Balan, F. Pietrucci, C. Gervais, M. Blanchard, J. Schott, J. Gaillardet, First-principles study of boron speciation in calcite and aragonite, Geochimica et Cosmochimica Acta, 193, 119-131 (2016)

C. Pinilla, M. Blanchard, E. Balan, R. Vuilleumier, F. Mauri, Equilibrium magnesium isotope fractionation between Mg2+(aq) and carbonate minerals: insights from path integral molecular dynamics, Geochimica et Cosmochimica Acta, 163, 126-139 (2016)

A. Zeidler, K. Wezka, D. A. J. Whittaker, P. S. Salmon, A. Baroni, S. Klotz, H. E. Fischer, M. C. Wilding, C. L. Bull, M. G. Tucker, M. Salanne, G. Ferlat, M. Micoulaut, Density-driven structural transformations in B2O3 glass, Physical Review B, 90, 024206 (2014) (link)

H. Yi, E. Balan, C. Gervais, L. Segalen, F. Fayon, D. Roche, A. Person, G. Morin, M. Guillaumet, M. Blanchard, M. Lazzeri, F. Babonneau, A carbonate-fluoride defect model for carbonate-rich fluorapatite. American Mineralogist (letter),98, 1066-1069 (2013)

G. Ferlat, A. P. Seitsonen, M. Lazzeri, F. Mauri, Hidden polymorphs drive vitrification in B2O3, Nature Materials, 11, 925-929 (2012) (link)

Researchers:

Etienne Balan, Guillaume Ferlat, Fabio Pietrucci