https://is.muni.cz/el/1431/podzim2006/C7780/um/Read/2711172/SAM_str_grwth_ProgSurfSci00_151.pdf

Structure and growth of self-assembling monolayers

The structural properties of free nanoclusters are reviewed. Special attention is paid to the interplay of energetic, thermodynamic, and kinetic factors in the explanation of cluster structures that are actually observed in experiments. The review starts with a brief summary of the experimental methods for the production of free nanoclusters and then considers theoretical and simulation issues, always discussed in close connection with the experimental results. The energetic properties are treated first, along with methods for modeling elementary constituent interactions and for global optimization on the cluster potential-energy surface. After that, a section on cluster thermodynamics follows. The discussion includes the analysis of solid-solid structural transitions and of melting, with its size dependence. The last section is devoted to the growth kinetics of free nanoclusters and treats the growth of isolated clusters and their coalescence. Several specific systems are analyzed.

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Structural properties of nanoclusters: Energetic, thermodynamic, and kinetic effects

Publisher Summary This chapter focuses on the concept of evaporative cooling of trapped neutral atoms. The recent observations of Bose–Einstein condensation have shown dramatically the potential of evaporative cooling. Through evaporative cooling, phase-space density could be increased by six orders of magnitude in these experiments. In such experiments, evaporative cooling was used to reach temperature and densities that are unprecedented for trapped atoms and greatly exceeded what had been reached before by laser cooling. Laser cooling has recently broken the recoil limit in three dimensions (3D) and reached extremely cold temperatures of 3 nK in 1D. However, none of these optical sub-recoil techniques has been realized so far at high densities. The current density limitations are caused by the absorption of light, radiation trapping, and excited state collisions. An often-mentioned disadvantage of evaporative cooling is the loss of atoms. However, as discussed in the chapter, the efficiency of evaporative cooling is quite high.

Evaporative Cooling of Trapped Atoms

Layered metal phosphates and phosphonates : from crystals to monolayers

A semiempirical pair potential for molecular hydrogen and deuterium has been derived by fitting to solid state data. The potential is bounded to conform asymptotically to short‐ and long‐range theoretical results. In the solid, many‐body effects are accounted for by including a spherical form of the nonnegligible Axilrod–Muto–Teller three‐body forces. The potential can be used to successfully describe isotropic properties in the solid and gas phases.

The isotropic intermolecular potential for H2 and D2 in the solid and gas phases

The present work reports on the equilibrium thermodynamic properties of small clusters of xenon, krypton, and argon atoms, determined from a biased random-walk Monte Carlo procedure. Cluster sizes ranged from 3 to 13 atoms. Each cluster was found to have an abrupt liquid-gas phase transition at a temperature much less than for the bulk material. An abrupt solid-liquid transition is observed for thirteen- and eleven-particle clusters. For cluster sizes smaller than 11, a gradual transition from solid to liquid occurred over a fairly broad range of temperatures. Distribution of number of bond lengths as a function of bond length was calculated for several systems at various temperatures. The effects of box boundary conditions are discussed. Results show the importance of a correct description of boundary conditions. A surprising result is the slow rate at which system properties approach bulk behavior as cluster size is increased.

Thermodynamic properties of small aggregates of rare-gas atoms

A biased random walk, Monte Carlo procedure is used to study the melting transition in small clusters of N atoms. Results show an abrupt change in physical properties near melting, but there is no evidence that the transition is either first or second order; rather the transition is more gradual.

On the character of the melting transition in small atomic aggregates

The zero-temperature equilibrium structure and orientations of solid ${\mathrm{N}}_{2}$ are calculated at pressures 20\ensuremath{\le}P\ensuremath{\le}415 kbar by optimizing the lattice energy of an eight-molecule unit cell with respect to a rhombohedral distortion of the crystal from the cubic Pm3n structure. The resulting equilibrium structures have R3\ifmmode\bar\else\textasciimacron\fi{}c(${C}_{3v}^{6}$) symmetry, upon which the pressure-volume relation and the libron, vibron, and lattice phonon frequencies at zone center are calculated using lattice dynamics. These quantities are compared with experiment and the symmetry assignments of the calculated and observed modes are given. Also calculated are the second virial coefficients, the \ensuremath{\alpha}-${\mathrm{N}}_{2}$ molar volume and sublimation energy, and the \ensuremath{\alpha}- and \ensuremath{\gamma}-${\mathrm{N}}_{2}$ vibron frequencies, versus pressure.

High-pressure static and dynamic properties of the R3-barc phase of solid nitrogen.

Properties of H2 are studied on the basis of an analytic anisotropic potential deduced from atomic orbital and perturbation calculations. The low-pressure solid results are based on a spherical average of the anisotropic potential. The ground state energy and the pressure-volume relation are calculated. The metal-insulator phase transition pressure is predicted. Second virial coefficients are calculated for H2 and D2, as is the difference in second virial coefficients between ortho and para H2 and D2.

Properties of solid and gaseous hydrogen, based upon anisotropic pair interactions

Thermodynamic properties of solid nitrogen are calculated over a variety of isotherms and isobars using a constant pressure Monte Carlo method with deformable, periodic boundary conditions. Vibron frequencies are calculated using a simple perturbation theory. In addition, pressure–volume relations, thermal expansion coefficients, structures, and phase transition pressures and temperatures are determined. In particular, the nature of the orientational disorder in the plastic crystal phases is examined by calculating a variety of orientational order parameters.

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Richard D. Etters

Papers

Thermodynamic properties of small aggregates of rare-gas atoms

On the character of the melting transition in small atomic aggregates

High-pressure static and dynamic properties of the R3-barc phase of solid nitrogen.

Properties of solid and gaseous hydrogen, based upon anisotropic pair interactions

Calculated thermodynamic properties and phase transitions of solid N2 at temperatures 0≤T≤300 K and pressures 0≤P≤100 GPa