Ab Initio Calculation of the Adhesion and Ideal Shear Strength of Planar Diamond Interfaces with Different Atomic Structure and Hydrogen Coverage

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Ab initio study on the surface chemistry and nanotribological properties of passivated diamond surfaces

Experimental findings indicate that the impressively low friction and wear of diamond in humid environments are determined by the surface passivation. In this paper, we investigate the relationship between the surface chemistry and the nanotribological properties of diamond surfaces. We consider the (2x1)-C(001) surface taking into account different terminations constituted of hydrogen, oxygen, and hydroxyl groups. We analyze the adsorbate geometry and the polarization of the surface bonds. We discuss the stability of the different surface terminations in different conditions, which account for the presence in the environment of H-2, O-2, and H2O molecules in different concentrations and we present the surface phase diagram. Finally, we report the calculated adhesion energy between the passivated surfaces and analyze its variation as a function both of the surface separation and of the surface relative lateral position. In this way, we provide information on the effect of the different adsorbates on the interaction between diamond surfaces and on the magnitude and anisotropy of friction forces

Load-Induced Confinement Activates Diamond Lubrication by Water

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Ab initio study on the surface chemistry and nanotribological properties of passivated diamond surfaces

Experimental findings indicate that the impressively low friction and wear of diamond in humid environments are determined by the surface passivation. In this paper, we investigate the relationship between the surface chemistry and the nanotribological properties of diamond surfaces. We consider the (2x1)-C(001) surface taking into account different terminations constituted of hydrogen, oxygen, and hydroxyl groups. We analyze the adsorbate geometry and the polarization of the surface bonds. We discuss the stability of the different surface terminations in different conditions, which account for the presence in the environment of H-2, O-2, and H2O molecules in different concentrations and we present the surface phase diagram. Finally, we report the calculated adhesion energy between the passivated surfaces and analyze its variation as a function both of the surface separation and of the surface relative lateral position. In this way, we provide information on the effect of the different adsorbates on the interaction between diamond surfaces and on the magnitude and anisotropy of friction forces

Interaction between Economic and Financial Development

This paper presents a model of financial and economic development which assumes the consumption of real resources by the financial sector. Financial development occurs endogenously as the economy reaches a critical threshold of economic development. Compared to financial autarky, financial intermediaries allocate savings, net of their costs of operation, to more productive investments. Whenever the technology financed by intermediaries is more capital-intensive than that operated in financial autarky, the growth effect of financial development is ambiguous. As a result, financial development may be unsustainable. However, when financial development is sustainable, the credit market becomes more competitive and more efficient over time, and this could eventually contribute to economic growth. Nonetheless, given monopolistic competition in the financial sector, the level of entry into the credit market is generally inefficient. For instance, with diminishing returns to specialisation, entrants might be too few at the early stages of economic development and too many later on