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FEDERICA LODESANI

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Pubblicazioni

2023 - Erratum for a new self‐consistent empirical potential model for multicomponent borate and borosilicate glasses (Journal of the American Ceramic Society, (2022), 105, 12, (7254-7271), 10.1111/jace.18681) [Articolo su rivista]
Bertani, M.; Pallini, A.; Lodesani, F.; Cocchi, M.; Menziani, M. C.; Pedone, A.
abstract

The manuscript contains a mistake in Equation (6) and an erroneous value of the B-ij term of B-O interaction in Table 2. An additional sentence is needed in paragraph 2.2. These errata acknowledge and correct the mistakes and add the needed information. The corrections do not lead to any changes in the results, discussion, and conclusion.

2023 - Evidence of Multiple Crystallization Pathways in Lithium Disilicate: A Metadynamics Investigation [Articolo su rivista]
Lodesani, F.; Menziani, M. C.; Urata, S.; Pedone, A.
abstract

Metadynamics simulations driven by using two X-ray diffraction peaks identified three alternative crystallization pathways of the lithium disilicate crystal from the melt. The most favorable one passes through the formation of disordered layered structures undergoing internal ordering in a second step. The second pathway involves the formation of phase-separated structures composed of nuclei of beta-cristobalite crystals surrounded by lithium -rich phases in which metasilicate chains are formed. The conversion of these structures to the stable lithium disilicate crystal involves an intermediate structure whose silicate layers are connected by silicate rings with the energy barrier of 2.5 kJ/mol per formula unit (f.u.). The third pathway is highly unlikely because of the huge energy barrier involved (20 kJ/mol per f.u.). This path also involves the passage through a phase-separated structure of an indefinite silica region surrounded mainly by amorphous lithium oxide.

2022 - Biasing crystallization in fused silica: An assessment of optimal metadynamics parameters [Articolo su rivista]
Lodesani, F.; Menziani, M. C.; Urata, S.; Pedone, A.
abstract

Metadynamics (MetaD) is a useful technique to study rare events such as crystallization. It has been only recently applied to study nucleation and crystallization in glass-forming liquids such as silicates, but the optimal set of parameters to drive crystallization and obtain converged free energy surfaces is still unexplored. In this work, we systematically investigated the effects of the simulation conditions to efficiently study the thermodynamics and mechanism of crystallization in highly viscous systems. As a prototype system, we used fused silica, which easily crystallizes to β-cristobalite through MetaD simulations, owing to its simple microstructure. We investigated the influence of the height, width, and bias factor used to define the biasing Gaussian potential, as well as the effects of the temperature and system size on the results. Among these parameters, the bias factor and temperature seem to be most effective in sampling the free energy landscape of melt to crystal transition and reaching convergence more quickly. We also demonstrate that the temperature rescaling from T > Tm is a reliable approach to recover free energy surfaces below Tm, provided that the temperature gap is below 600 K and the configurational space has been properly sampled. Finally, albeit a complete crystallization is hard to achieve with large simulation boxes, these can be reliably and effectively exploited to study the first stages of nucleation.

2021 - Exploring the crystallization path of lithium disilicate through metadynamics simulations [Articolo su rivista]
Lodesani, F.; Tavanti, F.; Menziani, M. C.; Maeda, K.; Takato, Y.; Urata, S.; Pedone, A.
abstract

Understanding the crystallization mechanism in silica-based materials is of paramount importance to comprehend geological phenomena and to design novel materials for a variety of technological and industrial applications. In this work, we show that metadynamics simulations can effectively overcome a large energy barrier to crystallize from viscous oxide glass melts and can be used to identify the melt-to-crystal transition path of the lithium disilicate system. The accelerated atomistic simulation revealed of a two-step mechanism of the nanoscale crystal formation. First, a partially layered silica embryo appeared, and then a more ordered crystalline layer with size larger than the critical nucleus size was formed. Subsequently, lithium ions piled up around the silicate layer and triggered stacking of adjacent silicate layers, which eventually built a perfect crystal. Contrarily to previous hypotheses, no lithium metasilicate crystal was observed as a precursor of the homogeneous crystallization of lithium disilicate.

2021 - Investigation of alumino-silicate glasses by coupling experiments and simulations: Part I - Structures [Articolo su rivista]
Delaye, J. -M.; Gac, A. L.; Macaluso, S.; Angeli, F.; Lodesani, F.; Charpentier, T.; Peuget, S.
abstract

A set of alumino-silicate glasses with SiO2-Al2O3-Na2O-CaO compositions was investigated using Raman and NMR spectroscopy techniques and by classical molecular dynamics, in order to study the structural modifications which occur when CaO progressively replaces Na2O and when Al2O3 progressively replaces SiO2. The effect of a gradual increase in the Al2O3 content was also studied. Al was always 4 coordinated for all the compositions studied, including the peraluminous glasses. An increase in the number of Al-O-Al bonds was found when the Al2O3 or CaO content increases. The study confirmed that AlO4 groupings are preferentially compensated by Na rather than by Ca, and that there are non-bridging oxygens surrounded by mixed environments containing both Na and Ca. Combining the information given by the Raman and NMR spectroscopy results enabled the attribution of the Raman band at 570cm-1 to the Si-O-Al bonds. It confirmed that the band at 510cm-1 can be attributed to the Al-O-Al bonds, while that at 985cm-1 can be attributed to the Q4-Al entities. Lastly, it was demonstrated that the classical molecular dynamics potentials of Deng et al., specifically developed for this type of glasses, permit the reproduction of a large number of the experimental results quantitatively or sometimes simply qualitatively.

2021 - Investigation of alumino-silicate glasses by coupling experiments and simulations: Part II - radiation effects [Articolo su rivista]
Delaye, J. -M.; Le Gac, A.; Macaluso, S.; Angeli, F.; Lodesani, F.; Charpentier, T.; Peuget, S.
abstract

A set of SiO2-Al2O3[sbnd]Na2O[sbnd]CaO glasses with varying Si/Al and Na/Ca ratios was experimentally irradiated with Au4+ ions at 7.3MeV. Measurements by optical interferometry showed that, depending on the glass composition, the density could increase or decrease. Overall the higher the original quantity of non-bridging O, the greater the swelling observed. In order to explain the origin of these observations, some of the experimentally studied glasses were simulated by classical molecular dynamics and then subjected to a series of 4 keV displacement cascades or quenched at different rates. Comparisons of the density changes and atomic-scale modifications have allowed the authors to propose a phenomenological density change model. There appears to have been a competition between two processes with a first process where the vitreous structure “breathes” associated with the deposit of free volumes within the cascades that favours swelling. A second process is associated with changes in the local environments (creation of non-bridging O and of 3-coordinated O, creation of 5-coordinated Al, conversions between charge compensators and network modifiers) which act as brakes on the swelling. Depending on the relative dominance of these two processes, the glass may swell or contract.

2020 - Disclosing crystal nucleation mechanism in lithium disilicate glass through molecular dynamics simulations and free-energy calculations [Articolo su rivista]
Lodesani, F.; Menziani, M. C.; Maeda, K.; Takato, Y.; Urata, S.; Pedone, A.
abstract

Unraveling detailed mechanism of crystal nucleation from amorphous materials is challenging for both experimental and theoretical approaches. In this study, we have examined two methods to understand the initial stage of crystal precipitation from lithium disilicate glasses using molecular dynamics simulations. One of the methods is a modified exploring method to find structurally similar crystalline clusters in the glass models, enabling us to find three different embryos, such as Li2Si2O5 (LS2), Li2SiO3 (LS) and Li3PO4 (LP), in the 33Li2O·66SiO2·1P2O5 glass (LS2P1), in which P2O5 is added as a nucleating agent. Interestingly, LS2 and LP crystals were found inside the LS2P1 glass while LS crystal appeared on the glass surface, which agrees with experimental observations. The other method is free energy calculation using a subnano-scale spherical crystal embedded in the glass model. This method, which we called Free-Energy Seeding Method (FESM), allows us to evaluate free energy change as a function of crystal radius and to identify critical size of the crystal precipitation. The free energy profiles for LS and LS2 crystal nuclei in the LS2 glass models possess maximum energy at a critical radius as expected by classical nucleation theory. Furthermore, the critical radius and the energy barrier height agree well with recent experimental investigation, proving the applicability of this method to design glass–ceramics by atomistic modeling.

2020 - Structural origins of the Mixed Alkali Effect in Alkali Aluminosilicate Glasses: Molecular Dynamics Study and its Assessment [Articolo su rivista]
Lodesani, Federica; Menziani, Maria Cristina; Hijiya, Hiroyuki; Takato, Yoichi; Urata, Shingo; Pedone, Alfonso
abstract

The comprehension of the nonlinear effects provided by mixed alkali effect (MAE) in oxide glasses is useful to optimize glass compositions to achieve specific properties that depend on the mobility of ions, such as the chemical durability, glass transition temperature, viscosity and ionic conductivity. Although molecular dynamics (MD) simulations have already been applied to investigate the MAE on silicates, less effort has been devoted to study such phenomenon in mixed alkali aluminosilicate glasses where alkali cations can act both as modifiers, forming non-bridging oxygens and percolation channels, and as charge compensator of the AlO4− units present in the network. Moreover, the ionic conductivity has not been computed yet; thus, the accuracy of the atomistic simulations in reproducing the MAE on the property is still open to question. In this work, we have validated five major interatomic potentials for the classical MD simulations by modelling the structure, density, glass transition temperature and ionic conductivity for three aluminosilicate glasses, (25 − x)Na2O − x(K2O) − 10(Al2O3) − 65(SiO2) (x = 0, 12.5, 25). It was observed that only the core-shell (CS) polarizable force field well reproduces the experimentally measured MAE on Tg and the ionic conductivity as well as the higher conductivity of single sodium aluminosilicate glass at low temperature and the higher conductivity of single potassium aluminosilicate glass at high temperature. The MAE is related to the suppression of jump events of the alkaline ions between dissimilar sites in the percolation channels consisting of both sodium and potassium ions as in the case of alkaline silicates. The superior reproducibility of the CS potential is originated from the larger and the flexible ring structures due to the smaller Si-O-Si inter-tetrahedra angle, creating appropriate percolation channels for ion conductivity. We also report detailed assessments for using the potential models including the CS potential for investigating MAE on aluminosilicates.

2016 - Supercritical CO2 Confined in Palygorskite and Sepiolite Minerals: A Classical Molecular Dynamics Investigation [Articolo su rivista]
MUNIZ MIRANDA, Francesco; Lodesani, Federica; Tavanti, Francesco; Presti, Davide; Malferrari, Daniele; Pedone, Alfonso
abstract

We have investigated the ability of two modular phyllosilicates (palygorskite and sepiolite) to store CO2 molecules inside their structural channels by means of classical molecular dynamics. Several models containing an increasing supercritical-CO2/H2O ratio into the phyllosilicate channels have been built and the structural and dynamic properties of carbon dioxide and water molecules investigated in detail. We found that both clay minerals can achieve this goal, with sepiolite being able to store more carbon dioxide molecules (and more stably) than palygorskite, due to the larger channels of the former. Interestingly, with the increase of CO2 molecules inside the minerals, the diffusivity of both water and carbon dioxide drastically decreases and carbon dioxide molecules tend to arrange themselves in an ordered pattern. (Figure Presented).