Atomistic simulation of the free energies of dissolution of ions from flat and stepped calcite surfaces

Spagnoli, Dino; Kerisit, Sebastien N.; Parker, Stephen C.

doi:10.1016/j.jcrysgro.2006.05.030

Cited by 61 publications

(97 citation statements)

References 30 publications

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“…Experimental observations of calcite surfaces [12,54] show a high density of steps, where carbonate dissolution at the pH of interest (around nine) is more favorable [55], which is also predicted by theory [56]. Even stable surfaces such as the ð1 0 1 4Þ surface have been shown to reconstruct in moist air via pit formation and film growth [57], making it reasonable to consider defective stepped surfaces in our simulations.…”

Section: Resultssupporting

confidence: 67%

Growth modification of seeded calcite using carboxylic acids: Atomistic simulations

Aschauer

Spagnoli

Bowen

et al. 2010

Journal of Colloid and Interface Science

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a b s t r a c tMolecular dynamics simulations were used to investigate possible explanations for experimentally observed differences in the growth modification of calcite particles by two organic additives, polyacrylic acid (PAA) and polyaspartic acid (p-ASP). The more rigid backbone of p-ASP was found to inhibit the formation of stable complexes with counter-ions in solution, resulting in a higher availability of p-ASP compared to PAA for surface adsorption. Furthermore the presence of nitrogen on the p-ASP backbone yields favorable electrostatic interactions with the surface, resulting in negative adsorption energies, in an upright (brush conformation). This leads to a more rapid binding and longer residence times at calcite surfaces compared to PAA, which adsorbed in a flat (pancake) configuration with positive adsorption energies. The PAA adsorption occurring despite this positive energy difference can be attributed to the disruption of the ordered water layer seen in the simulations and hence a significant entropic contribution to the adsorption free energy. These findings help explain the stronger inhibiting effect on calcite growth observed by p-ASP compared to PAA and can be used as guidelines in the design of additives leading to even more marked growth modifying effects.

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Section: Resultssupporting

confidence: 67%

Growth modification of seeded calcite using carboxylic acids: Atomistic simulations

Aschauer

Spagnoli

Bowen

et al. 2010

Journal of Colloid and Interface Science

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“…Dissolving a Ca ion from a step was found to be more favourable than from a flat surface by over 100 kJmol −1 . The difference is significantly less when considering a CO 3 ion, but is still substantial at ∼10 kJmol −1 [42].…”

Section: Dissolution Processesmentioning

confidence: 95%

“…The removal of a Ca ion required ∼275 kJmol −1 of energy. A similar procedure was followed for the dissolution of a CO 3 ion, and the free energy of dissolution was found to be ∼30 kJmol −1 [42]. The same study also considered the removal of ions sitting on top of the flat surface, 'on-top' ions.…”

Section: Dissolution Processesmentioning

confidence: 96%

“…The angle of the step allowed two new H 2 O adsorption sites to appear, leading to a much higher water density at the step. When a CO 3 ion was removed the effect on the overall water density was very similar, although only one new adsorption site at the step appeared [42].…”

Section: −mentioning

confidence: 97%

“…At the acute step the second H 2 O initially coordinated with a particular Ca ion delocalised between two possible adsorption sites, implying the H 2 O was less strongly bound to the stepped surface than a flat surface. At the obtuse step, because the step created more room, two new adsorption sites appeared on the surface, making the water density much greater at the obtuse step than at the acute step [42].…”

Section: Steps and Kinksmentioning

confidence: 99%

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Investigation of the Interaction of Water with the Calcite (10.4) Surface Using Ab Initio Simulation

2009

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Density functional theory calculations were employed to explore the interaction between water and the {1014} surface of calcite. In addition a defective {1014} surface and stepped surfaces in contact with water were investigated. A series of percentage water coverages and water configurations were explored, including dissociated water states. Static relaxations found associated water to be favourable on the {1014} surface, although a metastable dissociated state 1.77eV higher in energy was found.Molecular dynamics (MD) simulations of low water coverage reveal fluctuations in the H-O water bond when the H atom is directed towards a surface CO 3 ion. Desorption of an H 2 O molecule was observed in simulations above 900K. Water was found to be strongly bound to the perfect {1014} surface, with an adsorption energy of -0.91eV. MD simulations of a defective {1014} surface found water to favour dissociation at CO 3 vacancies. However, water at Ca vacancies diffused across the surface to form a bond with the nearest surface Ca ion. Water was also found to favour an associated state at both acute and obtuse steps. On all these imperfect surfaces water was found to adsorb strongly to the surface, with adsorption energies ranging from -0.99eV to -1.60eV.

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Physico‐Chemical Principles of Crystallization

Cölfen

Antonietti

2008

Mesocrystals and Nonclassical Crystallization

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Atomistic simulation of the free energies of dissolution of ions from flat and stepped calcite surfaces

Cited by 61 publications

References 30 publications

Growth modification of seeded calcite using carboxylic acids: Atomistic simulations

Growth modification of seeded calcite using carboxylic acids: Atomistic simulations

Investigation of the Interaction of Water with the Calcite (10.4) Surface Using Ab Initio Simulation

Physico‐Chemical Principles of Crystallization

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