Physics
Permanent URI for this communityhttp://hdl.handle.net/1903/2269
Browse
69 results
Search Results
Item Triangular lattice gas with first- and second-neighbor exclusions: Continuous transition in the four-state Potts universality class(American Physical Society, 1984) Bartelt, N. C.; Einstein, Theodore L.Using phenomenological renormalization (transfer-matrix scaling), we have reexamined the phase transition of a triangular lattice gas with particles having both nearest- and second-nearest-neighbor exclusions. Widely accepted classical studies indicated that disordering of the ordered (p(2x2)) state is first order. In contradiction, we show that the transition is second order; its exponents are consistent with the four-state Potts model universality class, in accord with its Landau-Ginzburg-Wilson Hamiltonian classification.Item Summary Abstract: Pseudodipole selection rules for extended fine structure in APS: Calculations and applications.(AIP, 1984) Mehl, M. J.; Einstein, Theodore L.; Bryant, G. W.Item Summary Abstract: Relationship between many-parameter lattice gas systems and simpler models: Easy approximations for Tc(AIP, 1984) Bartelt, N. C.; Einstein, Theodore L.; Williams, Ellen D.Item Optimization of data end points and taper width in extended absorption fine-structure analysis(American Physical Society, 1984) Hershfield, Selman P.; Einstein, Theodore L.The dependence of deduced interatomic spacing and inner potential on the lower and upper limits of integration, k1 and k2, as well as the taper width D, was studied for extended absorption fine structure using sinusoidal model data. The optimal values are achieved when 2(k1+k2)R or 2(k2?k1?D)R equals an odd half-integral multiple of pi (rather than when 2k1R and 2k2R are integral multiples of pi), where R is the spacing. Analytic approximations are used to elucidate numerical computations. Optimization of D is also discussed.Item Critical Exponents of a Four-State Potts Chemisorbed Overlayer: p(2x2) Oxygen on Ni(111)(American Physical Society, 1981) Roelofs, L. D.; Kortan, A. R.; Einstein, Theodore L.; Park, Robert L.We report the first determination of critical exponents for a chemisorbed overlayer, using low-energy electron diffraction. We examine the order-disorder transition of p(2x2) oxygen on the (111) surface of nickel. This study is the first of critical behavior of a two-dimensional system in the four-state Potts universality class. Discussion of disparity between our results and predicted exponents considers several possibilities, including logarithmic corrections.Item Extended Appearance-Potential Fine-Structure Analysis: Oxygen on Al(100)(American Physical Society, 1980) Laramore, G.E.; Einstein, Theodore L.; Roelofs, L. D.; Park, Robert L.To measure O-Al separation at Al(100) surfaces disordered (low-energy electron-diffraction beams extinguished) by reaction with oxygen, the extended appearance-potential fine structure was analyzed above the threshold for electron-bombardment excitation of the O 1s core. Calculation shows that the outgoing electron has angular momentum l=0, allowing simple Fourier inversion of the fine structure. The separation, 1.9+-0.05 A, suggests that oxygen lies under the top layer, a result undetectable in extended-x-ray-absorption fine-structure measurements on thicker films.Item Unified view of step-edge kinetics and fluctuations(American Physical Society, 1998) Khare, S. V.; Einstein, Theodore L.We study theoretically the equilibrium fluctuations of steps on vicinal surfaces. From an analytical continuum description of the step edge, we find a single Langevin equation governing the motion of an isolated step around its equilibrium position that includes attachment/detachment of atoms, diffusion over the terrace, diffusion along the edge, and evaporation. We then extend this approach to treat an array of steps, i.e., a vicinal surface. We also present, in an appendix, an alternative formalism in which detachment to terrace and to step-edge diffusion can take place independently. In established as well as some new limits, and for numerous special cases, we study the wave-vector dependence—both exponent and prefactor—of the relaxation time of fluctuations. From this we recover scaling relations for early-time dependence of the mean-square fluctuations. We discuss how to extract the (mesoscopic) transport coefficients associated with different atomistic mechanisms of surface mass transport and how to distinguish between mechanisms having the same power-law dependence on wavelength in the capillary-wave analysis. To examine the crossovers between limiting regimes, we compute and explore an effective exponent for this power law and show that the crossover occurs over a narrow region of phase space. Furthermore, we find that single-sided approximations are valid only in the limit of extreme Schwoebel barriers.Item Stress Relief in Reconstruction(American Physical Society, 1997) Bach, Claudia E.; Giesen, Margret; Ibach, Harald; Einstein, Theodore L.We report on the first direct measurement of the change of the surface stress in the reconstruction of the Au(111) and the Au(100) surfaces. For both surfaces the reconstruction relaxes the intrinsic tensile stress, by 22 percent and 5 percent, respectively. A discussion of the data on the Au(111) surface in the Frenkel-Kontorova model shows that the energy gain due to the surface stress is not quite large enough to make the reconstructed phase energetically favored without the formation of the secondary herringbone structure of the solitons. On the Au(100) surface, the gain in elastic strain energy is clearly insufficient to cause the surface to reconstruct.Item Edge Diffusion during Growth: The Kink Ehrlich-Schwoebel Effect and Resulting Instabilities(American Physical Society, 1999) Pierre-Louis, O.; D'Orsogna, M. R.; Einstein, Theodore L.The morphology of surfaces of arbitrary orientation in the presence of step and kink Ehrlich-Schwoebel effects (SESE and KESE) during growth is studied within the framework of a model in which steps are continuous lines, and is illustrated by a simple solid-on-solid model. For vicinal surfaces KESE induces an instability often stronger than that from SESE. The possibility of stable kink flow growth is analyzed. Fluctuations can shift the stability threshold. KESE also induces mound formation.Item Bending-rigidity-driven transition and crumpling-point scaling of lattice vesicles(American Physical Society, 1996) Orlandini, E.; Stella, A. L.; Einstein, Theodore L.; Tesi, M. C.; Beichl, I.; Sullivan, F.