Ted Einstein
University of Maryland, Physics, Faculty Member
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Great progress has been made in the theory of the critical properties of phase transitions of lattice gases in two dimensions, but nature has provided very few realizations. Systems of chemisorbed atoms may well offer examples of the... more
Great progress has been made in the theory of the critical properties of phase transitions of lattice gases in two dimensions, but nature has provided very few realizations. Systems of chemisorbed atoms may well offer examples of the small number of universality classes, but one must worry about whether the limited size of defect-free regions precludes close enough approach to the critical regime to obtain scaling over a reasonable range and so whether the measured, effective exponents resemble the expected pure exponents. These concerns were heightened by the disagreement between expected and measured exponents for 0/Ni(111) [1]. To check what might be measured under ideal circumstances, we performed extensive Monte Carlo calculations [2–5] on lattices of about 4000 sites, comparable to the size of defect-free regions on metal surfaces. We assumed periodic boundary conditions and used lattice boundaries with the full symmetry of the substrate, i.e. hexagonal for triangular lattices...
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Near a second-order phase boundary, integrated intensities of “extra” LEED beams exhibit a |T -Tc|1-α singularity, where α is the specific heat critical exponent. We discuss the origin of this effect, apply it to real and... more
Near a second-order phase boundary, integrated intensities of “extra” LEED beams exhibit a |T -Tc|1-α singularity, where α is the specific heat critical exponent. We discuss the origin of this effect, apply it to real and Monte-Carlo-generated data, and comment on generalizations.
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This report discusses the progress at the University of Maryland Department of Physics on the adsorption of atoms or molecules on the surfaces of metals. Also discussed are: Phase transformation studies; the use of transfer matrices to... more
This report discusses the progress at the University of Maryland Department of Physics on the adsorption of atoms or molecules on the surfaces of metals. Also discussed are: Phase transformation studies; the use of transfer matrices to study the 2-d, 3-state chiral Potts model; electron-induced ionization of core electrons of atoms; the reflected electron energy loss fine structure above the M/sub 2,3/ core excitation edge of Cu; and other research in atomic and solid state physics. (LSP)
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Research Interests: Molecular Physics, Chemistry, Self Assembly, Nanotechnology, Medicine, and 15 moreMultidisciplinary, Fullerenes, Computer Simulation, Silver, Nanostructures, Interfaces, Metal, Interface, Fluctuations, Particle Size, Surface Properties, Molecular Conformation, Materials Testing, Molecule, and Amplitude
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Atomic steps are common defects at surfaces that can play an important role in many phenomena. Advances in the fabrication of nanostructures at surfaces depend largely upon the degree to which one can understand and control factors that... more
Atomic steps are common defects at surfaces that can play an important role in many phenomena. Advances in the fabrication of nanostructures at surfaces depend largely upon the degree to which one can understand and control factors that affect step morphology. The step line tension is a crucial element in the Gibbs-Thomson relation, which describes the dependence of the chemical
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The response of the Cu(111) Shockley surface state to an external electrical field is characterized by combining a density-functional theory calculation for a slab geometry with an analysis of the Kohn-Sham wavefunctions. Our analysis is... more
The response of the Cu(111) Shockley surface state to an external electrical field is characterized by combining a density-functional theory calculation for a slab geometry with an analysis of the Kohn-Sham wavefunctions. Our analysis is facilitated by a decoupling of the Kohn-Sham states via a rotation in Hilbert space. We find that the surface state displays isotropic dispersion, quadratic until the Fermi wave vector but with a significant quartic contribution beyond. We calculate the shift in energetic position and effective mass of the surface state for an electrical field perpendicular to the Cu(111) surface; the response is linear over a broad range of field strengths. We find that charge transfer occurs beyond the outermost copper atoms and that accumulation of electrons is responsible for a quarter of the screening of the electrical field. This allows us to provide well-converged determinations of the field-induced changes in the surface state for a moderate number of layers...
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To simulate epitaxial growth, one needs an a priori understanding of how atomic diffusion barriers depend on the occupation of near-neighbor sites of the initial and final positions. From a histogram of such barriers computed for... more
To simulate epitaxial growth, one needs an a priori understanding of how atomic diffusion barriers depend on the occupation of near-neighbor sites of the initial and final positions. From a histogram of such barriers computed for Cu/Cu(100) using the embedded atom method (EAM), Karimi et al.(M. Karimi, T. Tomkowski, G. Vidali, and O. Biham, Phys. Rev. B 52), 5364 (1995); O. Biham et al., preprint found that these energies fell into four groups. They proposed a simple approximation for the local-configuration dependence of the energy barriers. From a reexamination of these energies, using effective medium theory, we propose an approximation which also depends solely on near-neighbor occupations but accounts better for the energy barriers. The scheme is comparably accurate for Ag/Ag(100), but requires some modification for Ni/Ni(100). We also describe some noteworthy effects of fcc geometry in this approximation, particularly a mechanism which, like the Ehrlich-Schwoebel barrier, enha...
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Research Interests: Engineering, Physics, Thermodynamics, Crystal Growth, Statistical Physics, and 12 moreMathematical Sciences, Ising Model, Physical sciences, Nearest Neighbor, CHEMICAL SCIENCES, Learning Theory and Modeling, American physical society, Low Temperature, Surface Energy, Thermal Properties, Spectral Density, and Physics Letters A
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Abstract. For detailed applications of lattice gas models to surface systems, mul-tisite interactions often play at least as significant a role as interactions between pairs of adatoms that are separated by a few lattice spacings. We... more
Abstract. For detailed applications of lattice gas models to surface systems, mul-tisite interactions often play at least as significant a role as interactions between pairs of adatoms that are separated by a few lattice spacings. We recall that trio (3-adatom, non-pairwise) interactions do not inevitably create phase-boundary asym-metries about half coverage. We discuss a sophisticated application to an experi-mental system and describe refinements in extracting lattice-gas energies from cal-culations of total energies of several different ordered overlayers. We describe how lateral relaxations complicate matters when there is direct interaction between the adatoms, an issue that is important when examining the angular dependence of step line tensions. We discuss the connector model as an alternative viewpoint and close with a brief account of recent work on organic-molecule overlayers. 1.1