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Articles 1 - 11 of 11

Full-Text Articles in Physics

Morphology And Ordering In Thin Liquid-Crystal Films On Flat Glass Substrates, Yushan Shi, Brian Cull, Satyendra Kumar Oct 1993

Morphology And Ordering In Thin Liquid-Crystal Films On Flat Glass Substrates, Yushan Shi, Brian Cull, Satyendra Kumar

Physics Publications

Results of a high resolution x-ray reflectivity study of growth morphology and ordering of thin liquid-crystal films on flat glass substrate are reported. An adsorbed bilayer of crystalline order, under three dimensional clusters, was found to persist well beyond the nematic to isotropic transition. This adsorbed layer appears to be related to the surface memory effects in liquid-crystal devices. The morphology of these films can be described by the Stranski-Krastanov growth mode.


Theory Of A Symmetry-Breaking Phase-Transition In A Surface-Layer Of Nematic Liquid-Crystal, Y. L'Vov, R. M. Hornreich, David W. Allender Aug 1993

Theory Of A Symmetry-Breaking Phase-Transition In A Surface-Layer Of Nematic Liquid-Crystal, Y. L'Vov, R. M. Hornreich, David W. Allender

Physics Publications

For a surface interaction linear in the order parameter and favoring an orientation in which liquid-crystalline molecules lie parallel to the surface (but which is independent of whether the orientation is uniaxial or isotropic in the bounding plane), a symmetry-breaking phase transition in a surface layer is possible at temperatures above that of the bulk isotropic to nematic transition. At the surface transition, the high-temperature in-plane isotropic state becomes unstable with respect to a biaxial phase, the transition being continuous and therefore of-the Berezinskii-Kosterlitz-Thouless (BKT) type, It is expected to occur for intermediate surface couplings but not at very weak ...


Correct Phase-Diagrams Of Liquid-Crystals Reported To Exhibit The (Nonexistent) Incommensurate Smectic-A Phases, P. Patel, Satyendra Kumar Jul 1993

Correct Phase-Diagrams Of Liquid-Crystals Reported To Exhibit The (Nonexistent) Incommensurate Smectic-A Phases, P. Patel, Satyendra Kumar

Physics Publications

Three different incommensurate phases predicted by the phenomenological theory of frustrated smectics were reportedly found in mixtures of DB8OCN and 8OBCAB and DB7OCN and 8OCB. The results of our high-resolution X-ray diffraction study of these materials show that these phases are, indeed, coexistences of two or more smectic-A phases. The correct phase diagrams of the two systems are found to be in excellent agreement with the phenomenological models. At this time, there remain no known materials that exhibit an incommensurate smectic-A phase.


Phase-Diagram Of A Frustrated Smectic Liquid-Crystal System And The Absence Of The Incommensurate Smectic-A(I2) Phase, Prem Patel, Li Chen, Satyendra Kumar Apr 1993

Phase-Diagram Of A Frustrated Smectic Liquid-Crystal System And The Absence Of The Incommensurate Smectic-A(I2) Phase, Prem Patel, Li Chen, Satyendra Kumar

Physics Publications

The phase diagram and the structure of smectic-A(d) (Sm-A(d)) and Sm-A2 phases of binary mixtures of 4-octyloxy-4'-cyanobiphenyl (8OCB) and 4-n-heptyloxyphenyl-4'-cyanobenzoyloxybenzoate (DB7OCN) have been determined by high-resolution x-ray diffraction. This system had previously been reported by Ratna, Shashidhar, and Raja [Phys. Rev. Lett. 55, 1476 (1985)] to exhibit an incommensurate Sm-A(i2) phase for concentrations of 8OCB ranging from 25 to 40 mol %. The phase diagram obtained from the present study is in excellent agreement with the mean-field theory of Prost and co-workers [J. Phys. (Paris) 46, 391 (1985)]. The results of the x-ray study establish that ...


Phenomenological Theory Of Cuprate Superconductivity, Mario Rabinowitz, T. Mcmullen Jan 1993

Phenomenological Theory Of Cuprate Superconductivity, Mario Rabinowitz, T. Mcmullen

Physics Publications

Reasonably good agreement with the superconducting transitiontemperatures of the cuprate high‐T c superconductors can be obtained on the basis of an approximate phenomenological theory. In this theory, two criteria are used to calculate the superconducting transitiontemperature. One is that the quantum wavelength is of the order of the electron‐pair spacing. The other is that a fraction of the normal carriers exist as Cooper pairs at T c . The resulting simple equation for T c contains only two parameters: the normal carrier density and effective mass. We calculate specific transition temperatures for 12 cuprate superconductors.


Angular And Radial Correlation In Doubly Excited Systems When 1 ≤ Z ≤ 4. The 2p2 3p State, D. R. T. Keeble, K. E. Banyard, Gordon W. F. Drake Jan 1993

Angular And Radial Correlation In Doubly Excited Systems When 1 ≤ Z ≤ 4. The 2p2 3p State, D. R. T. Keeble, K. E. Banyard, Gordon W. F. Drake

Physics Publications

The angular and radial components of electron correlation have each been examined in detail for the discrete 2p2 3P states of H-, He, Li+ and Be2+. These doubly excited systems were described by highly accurate explicitly correlated wavefunctions. The analysis involved the use of angular Coulomb holes, changes in the one- and two-particle radial density distributions and several angular and radial expectation values. Additionally, various statistical correlation coefficients were used which emphasized, in turn, angular and radial correlation properties in different regions of the two-particle density. The angular holes and related properties showed a clearly defined inverse-Z effect for He ...


1/N Expansions For Two-Electron Coulomb Matrix Elements, Gordon W. F. Drake, R. N. Hills Jan 1993

1/N Expansions For Two-Electron Coulomb Matrix Elements, Gordon W. F. Drake, R. N. Hills

Physics Publications

The study of 1/n expansions for various atomic matrix elements, where n is the principal quantum number, plays an important role in the theoretical foundations of the quantum defect method. The paper develops an expansion in powers of 1/n 2 for hydrogenic boundstate wavefunctions which can be used to calculate 1/n expansions of matrix elements. The 1/n expansions of the two-electron direct and exchange Coulomb integrals are evaluated as an example. © 1993 IOP Publishing Ltd.


Energy Corrections Of Order Mc2Α6lnα In Helium, Gordon W. F. Drake, I. B. Khriplovich, A. I. Milstein, A. S. Yelkhovsky Jan 1993

Energy Corrections Of Order Mc2Α6lnα In Helium, Gordon W. F. Drake, I. B. Khriplovich, A. I. Milstein, A. S. Yelkhovsky

Physics Publications

Quantum-electrodynamic corrections of O(mc2α6lnα) to the electron-electron interaction in helium are evaluated for several states. The additional energy shift, which is an order of α smaller than the leading Araki-Sucher terms, raises the predicted energy of the 1s2s 1S0 state by 2.49 MHz to -960 332 039.43(18) MHz relative to He+(1s). The new value significantly alters the comparison with recent high-precision experiments. © 1993 The American Physical Society.


Erratum: Energy Corrections Of Order Mc2Α6 In Α In Helium (Physical Review A (1993) 48, 6 (4804), Gordon W. F. Drake, I. B. Khriplovich, A. I. Milstein, A. S. Yelkhovsky Jan 1993

Erratum: Energy Corrections Of Order Mc2Α6 In Α In Helium (Physical Review A (1993) 48, 6 (4804), Gordon W. F. Drake, I. B. Khriplovich, A. I. Milstein, A. S. Yelkhovsky

Physics Publications

No abstract provided.


Erratum: Variational Calculation For The Ground State Of Lithium And Qed Corrections For Li-Like Ions (Physical Review A (1993) 48, 6 (4803)), D. K. Mckenzie, Gordon W. F. Drake Jan 1993

Erratum: Variational Calculation For The Ground State Of Lithium And Qed Corrections For Li-Like Ions (Physical Review A (1993) 48, 6 (4803)), D. K. Mckenzie, Gordon W. F. Drake

Physics Publications

No abstract provided.


A Fast Serial Algorithm For The Finite Temperature Quenched Potts Model, Gregory N. Hassold, Elizabeth A. Holm Jan 1993

A Fast Serial Algorithm For The Finite Temperature Quenched Potts Model, Gregory N. Hassold, Elizabeth A. Holm

Physics Publications

An efficient serial algorithm for finite temperature, quenched Potts model simulations of domain evolution has been developed. This ''n‐fold way'' algorithm eliminates unsuccessful spin flip attempts a priori by flipping sites with a frequency proportional to their site activity, defined as the sum of the probability of success for every possible spin flip at that site. Finite temperature efficiency for high‐spin degeneracy systems is achieved by utilizing a new, analytical expression for the portion of the site activity due to flips to non-neighbor spin values. Hence, to determine the activity of a site, only flips to the ...