Molecular-scale surface processes during the growth of calcite in the presence of manganese

Abstract

Abstract-This paper deals with the growth behaviour of the Mn-Ca-C0 3 -H 2 0 solid solution-aqueous solution system on calcite {1O I 4} surfaces. This system represents a model example, which allows us to study the effect of a number of controlling factors on the crystallisation: (1) the supersaturation function, (3(x), and nucleation rate function, J(x), for the Mn-Ca-C0 3 -H 2 0 system, (2) the relationship of such functions to the molecular scale growth mechanisms operating on growing surfaces, and (3) the surface structure of the calcite {1O I 4} faces. In situ atomic force microscopy (AFM) growth experiments revealed a wide variety of surface phenomena, such as the transition between growth mechanisms, anisotropic changes in the step rates, and the influence of the Mn-bearing newly formed surface on subsequent growth (step stoppage followed by the formation of two-dimensional nuclei and the reproduction of the original calcite {1014} surface microtopog raphy). These phenomena result from the interplay between the controlling parameters and are explained in those terms.

Nanoscale anglesite growth on the celestite (001) face

“…Thus, when a third monolayer reaches the strained area, growth is inhibited and the shapes of the original celestite etch pits are reproduced. The reproduction of such surface features on a nanoscale after monolayer growth is a common phenomenon observed in a number of experimental systems; it is often referred to as the template effect [14][15][16][17]. Although a conclusive explanation has not been reported yet, the template effect is often qualitatively explained by invoking compositional inhomogenities and their related lattice strains [12,14].…”

“…As a result, a reproduction of the original nanotopographic features (i.e. the so-called template effect) can occur [15][16][17]. Although this phenomenon seems to be related to the generation of strained areas on the first monolayers, a conclusive explanation has not been reported.…”

In situ AFM study of the interaction between calcite {101¯4} surfaces and supersaturated Mn2+–CO32− aqueous solutions

“…Regarding this, various works [4,5] have reported nanoscale observations, which indicate that the substrate also exerts a strong effect on the growth rate of layers forming from a multicomponent aqueous solution. The control exerted by the substrate is referred to as "template effect" [5,6]. It involves the retard of the step growth rate of successive monolayers that spread on a pure substrate.…”

Microbial Kinetic Controls on Calcite Morphology in Supersaturated Solutions

“…Our inorganic control medium is a more realistic simulation of natural conditions because it contains magnesium, phosphate, sulfate, and trace metals that coexist in many natural waters and are necessary for microbial growth. Although many of these inorganic ions are known to influence the growth and morphology of calcite (Astilleros et al 2002;Berner and Morse 1974;Fernández-Díaz et al 1996;Takasaki et al 1994;Tracy et al 1998), we did not monitor their concentrations in G20 basal medium after the precipitation experiment (Table 1). Therefore, we cannot discount the possibility that the uptake of trace amounts of inorganic inhibitors (e.g., phosphate) (Berner and Morse 1974) may additionally contribute to the observed differences in calcite morphology between active cultures and controls (Fig.…”