Nucleation delay in the anorthite-diopside binary system: Models and experiments

• Published in: Journal of non-crystalline solids 2020-10, Vol.546, p.120255, Article 120255
• Main Authors: Baker, Don R., Rusiecka, Monika K., Bilodeau, Maude, Kwon, Sun Yong
• Format: Article
• Language: English
• Subjects: Classical nucleation theory; Crystal nucleation; Nucleation delay; Thermodynamics of silicate systems; Transport properties of silicate melts
• ISSN: 0022-3093; 1873-4812
• DOI: 10.1016/j.jnoncrysol.2020.120255

•Nucleation delay of crystallization has been calculated by classical nucleation theory in the binary system anorthite (CaAl2Si2O8) – diopside (CaMgSi2O6).•The necessary parameters were extracted from previously published thermodynamic models of the system and diffusion and viscosity measurements in the literature.•Comparison with experimental data required an adjustment of the activation energy for transport across the melt-diopside nucleus for pure diopside, but the adjustment was within uncertainty of diffusion measurements in diopside melt.•The nucleation delay model reproduced nucleation delays in the two end-members and three intermediate compositions in the binary to within approximately a factor of 10.•Differences between modelled and measured nucleation delays are attributed to uncertainties in the underlying thermodynamic and transport properties of the system, particularly those related to the activation energy for transport across the melt-diopside nucleus. Nucleation delay was calculated for crystallization of anorthite (CaAl2Si2O8) and diopside (CaMgSi2O6) from melt, and for crystallization in 3 melts in the anorthite-diopside system using classical nucleation theory and values for equilibrium and transport properties from the literature. Calculations were compared to experiments in the literature and new experiments performed on diopside. Only one value, the activation energy of transport for diopside melt, was adjusted to fit the experiments. The activation energies, interfacial energies, and size of the structural unit of growth used for the end-member compositions were applied to calculate nucleation delays for three mixtures inside the binary. The calculated and experimental nucleation delays were within ~10x of each other, substantiating the use of classical nucleation theory to calculate nucleation delays in this system. Differences between measurements and calculations are probably due to uncertainties in equilibrium and transport properties of the system, particularly the activation energy for transport.