Howard L. Richards

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The pairwise Einstein model of steps not only justifies the use of the generalized Wigner distribution GWD for terrace width distributions TWDs , it also predicts a specific form for the step position distribution SPD , i.e., the probability density function for the fluctuations of a step about its average position. The predicted form of the SPD is well(More)
1 Magnetization switching in highly anisotropic single-domain ferromagnets has been previously shown to be qualitatively described by the droplet theory of metastable decay and simulations of two-dimensional kinetic Ising systems with periodic boundary conditions. In this article we consider the effects of boundary conditions on the switching phenomena. A(More)
The so-called generalized Wigner distribution has earlier been shown to be an excellent approximation for the terrace width distribution (TWD) of vicinal surfaces characterized by step-step interactions that are perpendicular to the average step direction and fall off as the inverse square of the step spacing. In this paper, we show that the generalized(More)
Measurement of terrace-width distributions ~TWD’s! of vicinal surfaces is used routinely to find the dimensionless strength à of the elastic repulsion between steps. For sufficiently strong repulsions, the TWD can be described by a Gaussian about the mean step spacing, but controversy has arisen on the correct prefactor in the relation of the TWD variance(More)
The magnetic relaxation of ferromagnetic powders has been studied for many years, largely due to its importance to recording technologies. However, only recently have experiments been performed that resolve the magnetic state of individual sub-micron particles. Motivated by these experimental developments, we use droplet theory and Monte Carlo simulations(More)
We present two recent applications of lattice-gas modeling techniques to elec-trochemical adsorption on catalytically active metal substrates: urea on Pt(100) and (bi)sulfate on Rh(111). Both systems involve the speciic adsorption of small molecules or ions on well-characterized single-crystal electrodes, and they provide a particularly good t between the(More)
Recently it has been recognized that the so-called generalized Wigner distribution may provide at least as good a description of terrace width distributions (TWDs) on vicinal surfaces as the standard Gaussian fit and is particularly applicable for weak repulsions between steps, where the latter fails. Subsequent applications to vicinal copper surfaces at(More)
Using reflection electron microscopy we examine the step fluctuations of Si~111! at 1100 °C. Evaporation is compensated by a replenishing flux. The step fluctuation behavior is qualitatively similar to that at 900 °C ~where sublimation is negligible!, with unexplained quantitative differences. We focus on the three parameters of the step continuum model of(More)
For more than three decades, measurement of terrace width distributions (TWDs) of vicinal crystal surfaces have been recognized as arguably the best way to determine the dimensionless strength ~ A of the elastic repulsion between steps. For suciently strong repulsions, the TWD is expected to be Gaussian, with ~ A varying inversely with the squared(More)
From quantitative measurement of the equilibrium terrace-width (`) distribution (TWD) of vicinal surfaces, one can assess the strength A of elastic step±step repulsions A/` 2. Generally the TWD depends only on ~ A ˆ A  …step stiffness†=…k B T† 2. From ideas of ¯uctuation phenomena, TWDs should be describable by thè`generalized Wigner distribution'' (GWD),(More)