18 research outputs found
Improved high-temperature expansion and critical equation of state of three-dimensional Ising-like systems
High-temperature series are computed for a generalized Ising model with
arbitrary potential. Two specific ``improved'' potentials (suppressing leading
scaling corrections) are selected by Monte Carlo computation. Critical
exponents are extracted from high-temperature series specialized to improved
potentials, achieving high accuracy; our best estimates are:
, , , ,
. By the same technique, the coefficients of the small-field
expansion for the effective potential (Helmholtz free energy) are computed.
These results are applied to the construction of parametric representations of
the critical equation of state. A systematic approximation scheme, based on a
global stationarity condition, is introduced (the lowest-order approximation
reproduces the linear parametric model). This scheme is used for an accurate
determination of universal ratios of amplitudes. A comparison with other
theoretical and experimental determinations of universal quantities is
presented.Comment: 65 pages, 1 figure, revtex. New Monte Carlo data by Hasenbusch
enabled us to improve the determination of the critical exponents and of the
equation of state. The discussion of several topics was improved and the
bibliography was update
Electrochemical Formation and Microstructure of Porous Gallium Phosphide
Electrochemical formation and microstructure of porous GaP have been investigated. Nanostructured porous GaP layers of thickness up to ≈ 20 μm were fabricated on n-type (111)-oriented crystalline c-GaP substrates. Studies of microstructure of porous GaP in dependence on electrolyte type and regimes of technological procedure have been carried out by scanning electron microscopy. The samples were characterized by spectroscopic ellipsometry in visible and near UV spectral range. The investigations have shown that the structure and optical response of porous GaP can be efficiently controlled by technological procedure of electrochemical formation. The shape and dimension of pores can be varied from nanometer-scaled cylindrical pores to GaP nanorods