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Inthis paper, we present simulations of two-dimensional islandson the barite (001) face. These simulations were performed with MMonCa,a computer code based on the kinetic Monte Carlo technique. Our resultsare in excellent agreement with previous in situatomicforce microscopy (AFM) observations. Indeed, MMonCa is able to preciselyreproduce both the thickness and the characteristic fan shape of barite(001) two-dimensional islands, which is defined by two straight stepsparallel to the ⟨120⟩ directions and a curved step connectingthem. In addition, MMonCa also simulates the orientation reversalof islands in successive growth monolayers. Fundamental for the adequatereproduction of the shape of barite (001) islands is the introductionof an anisotropy factor for the incorporation of growth units intocrystallographically nonequivalent step edges. The results presentedin this paper demonstrate that the consideration of simple crystallographicand geometrical constraints can be enough to provide a consistentexplanation for the development of complex nanotopographies duringthe growth of crystals. [ABSTRACT FROM AUTHOR]

Abstract: Crystal growth inhibition by non-incorporating impurities has been described and quantified since 1958 by the so-called step pinning model by Cabrera and Vermilyea [1]. In the original model, as well as in its recent improvements by Weaver et al. in 2006 and 2007 [2,3], only the inhibition by the adsorption of impurities on crystal surfaces with fixed compositions is considered. However, most of the crystals found in nature are solid solutions with more or less wide chemical variability. Therefore, in order to provide more realistic models of crystal growth inhibition in natural systems, it is fundamental to study in detail the inhibition of surfaces of solid solutions by non-incorporating impurities. In this paper, the Cabrera–Vermilyea model has been generalised for the case of growth inhibition in solid solution–aqueous solution (SS–AS) systems. This generalisation was made by considering that supersaturation and the physicochemical properties of the solid solutions are functions of the solid composition. The main implication of the model is that a progressive inhibition of growth of a solid solution by increasing the concentration of an adsorbed impurity results in compositional changes on the growing surfaces. [Copyright &y& Elsevier]

Abstract: In situ atomic force microscopy (AFM) was used to study the growth behaviour of anglesite (PbSO4) monolayers on the celestite (001) face. Growth was promoted by exposing the celestite cleavage surfaces to aqueous solutions that were supersaturated with respect to anglesite. The solution supersaturation, βang , was varied from 1.05 to 3.09 (where βang = a(Pb2 + )· a(SO4 2−)/Ksp,ang ). In this range of supersaturation, two single anglesite monolayers (∼3.5Å in height each) from pre-existent celestite steps were grown. However, for solution supersaturation βang <1.89±0.06, subsequent multilayer growth is strongly inhibited. AFM observations indicate that the inhibition of a continuous layer-by-layer growth of anglesite on the celestite (001) face is due to the in-plane strain generated by the slight difference between the anglesite and celestite lattice parameters (i.e. the linear misfits are lower than 1.1%). The minimum supersaturation required to overcome the energy barrier for multilayer growth gave an estimate of the in-plane strain energy: 11.4±0.6mJ/m2 . Once this energy barrier is overcome, a multilayer Frank–Van Der Merwe epitaxial growth was observed. [Copyright &y& Elsevier]

Abstract: In situ AFM experiments have been conducted in order to obtain information about kinetics of celestite epitaxial growth on barite. Growth has been promoted by passing aqueous solutions supersaturated with respect to celestite over freshly cleaved barite (001) surfaces. Solution supersaturation, β celestite, was varied from 1 to 45.7 . At supersaturations below 10 neither two-dimensional nucleation neither step advancement are observed on barite (001) surfaces. However, once the two-dimensional nucleation barrier is overcome (β celestite >10), nuclei preferentially form on cleavage steps parallel to [100], [110] and [120] directions and more scarcely on terraces. The subsequent growth of two-dimensional nuclei leads to the development of celestite “islands”. Their morphology is defined by (001) face and {210} and {100} forms and can be explained on the basis of PBC theory. The coalescence of such islands results in the formation of a homogeneous SrSO4 layer. Growth rates along [001] direction have been measured for the whole supersaturation range. The growth rate equation for “Birth and Spread” crystal growth mechanism has been successfully fitted to our experimental data. The fitting process has provided basic growth parameters in a good agreement with theoretical ones. Both the high transitional supersaturation required for two-dimensional nucleation and the high interfacial energy value obtained from the fitting of the “Birth and Spread” equation indicate low affinity of SrSO4 growth units for barite (001) faces. This is consistent with the relative high mismatch between celestite and barite structure. The behaviour of the epitaxial growth described in this work can help to interpret the oscillatory zoning frequently occurring in both natural and synthetic crystals of the Ba x Sr1−x SO4 solid solution. [Copyright &y& Elsevier]

This work presents a parallel approach of the Kinetic Monte Carlo (KMC) algorithm using a distributed memory architecture. The resulting computer software was tested by conducting crystal growth simulations on barite (001) face. Execution times, simulated times and crystallization velocities are compared with a shared memory parallel KMC software (MMonCa). Finally, a ≈ 1 μm2 crystal growth simulation is performed and compared with atomic force microscopy crystal growth experiments. The capability of this approach is demonstrated: a) a significant reduction of parallel overhead is achieved when comparing to the shared memory parallel version of the software, b) a distributed memory approach achieves an increase in memory resources enough to perform simulations with lattice sizes about 1 μm2, allowing the study of larger structures than those in shared memory or sequential implementations, c) this approach should be used only with large scale simulations to take advantage of the distributed memory architecture, d) further improvements are needed for parallel KMC to be faster than serial KMC in small scale simulations, e) the KMC algorithm used is able to adequately simulate two-dimensional nucleation on large areas of barite (001) faces. [ABSTRACT FROM AUTHOR]

The article presents an analysis of a study by Alexander G. Shtukenberg, Yurii O. Punin, and Pavel Azimov on crystal growth in binary solid solutions. It comments on the model used by the study on supersaturation and crystal growth rates in solid solution-aqueous solution systems. An examination of the study is provided.

Inthis article, we present a study of the epitaxial growth of nitratine(NaNO3) on calcite (CaCO3) from ethanolic solutions.By using sodium nitrate saturated solutions in ethanol we were ableto observe the initial stages of nitratine crystallization on calcite(10.4) cleaved surfaces with atomic force microscopy (AFM). Althoughthe oriented epitaxial growth of nitratine crystallites on calciteis independent from the solvent used (water, ethanol, or mixturesof them), the use of ethanolic solutions saturated with respect tonitratine is preferable for surface imaging in the AFM fluid cell.Additional nanotribology AFM experiments allowed us to measure shearstrengths necessary to remove crystallites of nitratine from calcite(10.4) faces. On the basis of both AFM observations and measured shearstrengths, the mechanism of epitaxial growth of nitratine on calcite(10.4) is discussed. [ABSTRACT FROM AUTHOR]

Abstract: Crystal growth has been promoted in the fluid cell of an Atomic Force Microscope (AFM) by passing Ba–Sr–SO4 aqueous solutions over barite (001) cleavage surfaces. Steps advance in structural continuity with the original barite (001) surfaces and two-dimensional nucleation occurs preferentially on the newly-formed terraces. The terraces are, on average, 7.5% lower than pure barite terraces. Since the ionic radius of Sr2+ is smaller that the ionic radius of Ba2+, the reduction of terrace height is consistent with an extensive incorporation of Sr2+ into the barite structure. Therefore, it can be considered that the newly-formed terraces have compositions corresponding to terms of the Ba x Sr1−x SO4 solid solution. A non-linear dependence of step rate on [SrSO4] concentration in the solution (and therefore on supersaturation) has been found. The growth behaviour has been discussed by considering both the physicochemical properties of the Ba x Sr1−x SO4 solid solution–aqueous solution (SS–AS) system and a kinetic-based step growth model. [Copyright &y& Elsevier]

• Zabuyelite (Li 2 CO 3) overgrowth was promoted on dolomite from aqueous solutions. • Overgrowths on dolomite formed using both supersaturated and undersaturated solutions. • Overgrowth friction coefficient is one order of magnitude lower than dolomite. Cleaved dolomite (CaMg(CO 3) 2) crystals were immersed in supersaturated, saturated, and undersaturated solutions with respect to zabuyelite (Li 2 CO 3), and the growth process was characterized using atomic force microscopy (AFM) and scanning electron microscopy (SEM). In all cases, overgrowths formed by 2D-nucleation could be clearly distinguished in the lateral force images recorded by AFM. With highly supersaturated solutions, AFM imaging was hindered by the formation of 3D crystal aggregates. When saturated solutions were used, the overgrowths reproduce the topography of the substrates, indicating that the lattice of the overgrown phase undergoes a compressive strain. Furthermore, we performed a nanotribological characterization by sliding a nanotip over both the 2D-overgrowths and dolomite substrates. Thus, friction coefficients, µ, could be easily quantified. As a result, a µ = 0.08 on the 2D-overgrowths was measured, which is one order of magnitude lower than the value of µ = 0.89 on the dolomite substrate. This friction reduction in the sliding of a nanotip on the overgrowth as compared to the friction observed on the dolomite substrate, together with the fact that atomic-scale stick-slip is observed on dolomite but not on the 2D overgrowths, point towards an anomalously weak interaction of Li 2 CO 3 overgrowths with the AFM probe. [ABSTRACT FROM AUTHOR]