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Clusterization of water molecules as deduced from statistical mechanical approach

100%

Krasnoholovets V.

Open Physics

2004

vol. 2

issue 4

698-708

Using the methods of statistical mechanics we have shown that a homogeneous water network is unstable and spontaneously disintegrates to the nonhomogeneous state (i.e. peculiar clusters), which can be treated as an ordinary state of liquid water. The major peculiarity of the concept is that it separates the paired potential into two independent components-the attractive potential and the repulsive one, which in turn should feature a very different dependence on the distance from the particle (a water molecule in the present case). We choose the interaction potential as a combination of the ionic crystal potential and the vibratory potential associated with the elastic properties of the water system as a whole. The number ℵ of water molecules that enters a cluster is calculated as a function of several parameters, such as the dielectric constant, the mass of a water molecule, the distance between nearest molecules, and the vibrations of nearest molecules in their nodes. The number of H2O molecules that comprise a cluster is estimated as about ℵ ≈ 900, which agrees with the available experimental data.

Mass-transport driven by surface instabilities in metals under reactive plasma/ion beam treatment at moderate temperature

84%

Pranevičius L., Milčius D., Pranevičius L., Širvinskaitë V., Nomgaudyte J., Rivier J.-P., Templier C.

Open Physics

2004

vol. 2

issue 1

67-89

This paper presents a generalized approach to the mechanisms of oxidation, hydrogenation and nitriding of metals under ion irradiation with reactive particles at elevated temperatures. Experimental results on the plasma oxidation of bilayered Y/Zr films, the plasma hydrogenation of Mg films and the ion beam (1.2 keV N2+) nitriding of stainless steel are presented and discussed. We make special emphasis on the analysis of surface effects and their role in the initiation of mixing of bilayered films, the ingress of reactive species in the bulk and the restructuring of the surface layers. It is suggested that primary processes driving reactive atoms from the surface into the bulk are surface instabilities induced by thermal and ballistic surface atom relocations under reactive adsorption and ion irradiation, respectively. The diffusion of adatoms and vacancies, at temperature when they become mobile, provide the means to relax the surface energy. It is recognized that the stabilizing effect of surface adatom diffusion is significant at temperatures below 300–350°C. As the temperature increases, the role of surface adatom diffusion decreases and processes in the bulk become dominant. The atoms of subsurface monolayers occupy energetically favorable sites on the surface, and result in reduced surface energy.

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2 Open Physics

2 2004

1 Krasnoholovets V.

1 Milčius D.

1 Nomgaudyte J.

1 Pranevičius L.

1 Rivier J.-P.

1 Templier C.

1 Širvinskaitë V.

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Clusterization of water molecules as deduced from statistical mechanical approach

Mass-transport driven by surface instabilities in metals under reactive plasma/ion beam treatment at moderate temperature