Showing papers by "Julia M. Yeomans published in 1985"
TL;DR: In this article, a low-temperature series analysis, taken to all orders by selecting important graphs at each stage, is used to demonstrate that an Ising system with an interface forced upon it exhibits an infinite sequence of first-order layering transitions as a function of applied magnetic field.
Abstract: It is shown that a low-temperature series analysis, taken to all orders by selecting important graphs at each stage, can be used to demonstrate that an Ising system with an interface forced upon it exhibits an infinite sequence of first-order layering transitions as a function of applied magnetic field. A model with a short-range surface potential, the Abraham model (1980), is also discussed and it is shown that it exhibits at least one layering transition at low temperatures.
61 citations
TL;DR: In this paper, a three-dimensional Ising model with competing interactions up to third-neighbour layers is analyzed using low-temperature series expansions and mean field theory.
Abstract: A three-dimensional Ising model with competing interactions up to third-neighbour layers is analysed using low-temperature series expansions and mean field theory. New sequences of phases springing from multiphase lines are found and the crossover to the behaviour of the ANNNI model is studied. Results are related to experimental findings on alloys, ferroelectrics, and polytypes.
32 citations
29 citations
TL;DR: In this article, a computer simulation technique is used to predict the lattice energies, structures and physical properties of magnesium silicate spinelloids from given interatomic potentials, and the calculated spinelloid polytypes are analyzed in terms of the interaction energies between component structural units.
Abstract: A computer simulation technique is used to predict the lattice energies, structures and physical properties of magnesium silicate spinelloids from given interatomic potentials. Two types of potential models are considered, a fully ionic model, which includes electrostatic, short-range and dispersive terms, and a partially ionic model, in which fractional charges are allocated to the component ions and a Morse function is included to describe the effect of covalency in the Si-O bond. The calculated energies of the spinelloid polytypes are analysed in terms of the interaction energies between component structural units. The calculated spinelloid energetics are discussed in the light of recently developed models of polytypism. The predicted values of the interaction energy terms are tested by using them to calculate the energy of a 1/21101](010) stacking fault in the naturally occurring magnesium silicate spinelloid wadsleyite. The calculated stacking-fault energies are in excellent agreement with the value inferred from transmission electron microscopy.
26 citations
TL;DR: In this article, a finite-size scaling calculation of the phase diagram of the two-dimensional, three-state, chiral clock model is used to study the phase dynamics.
Abstract: The authors use a finite-size scaling calculation to study the phase diagram of the two-dimensional, three-state, chiral clock model. Bulk properties, the ferromagnetic transition temperature and associated exponents are calculated from the scaling of the susceptibility and interface behaviour, the position of the interface wetting line and its exponents, from considering the net adsorption. They also present preliminary results on interface properties which are sensitive to the transition between the paramagnetic and incommensurate phases.
25 citations
TL;DR: In this paper, a low temperature series technique was used to study an Ising model with second and third neighbor competing interactions along one lattice direction, and six sequences of long wavelength commensurate phases were found to be stable at finite temperatures.
Abstract: We use a low temperature series technique to study an Ising model with second and third neighbour competing interactions along one lattice direction. Six sequences of long wavelength commensurate phases are found to be stable at finite temperatures. The results may well be relevant to ordering in polytypes and binary alloys.
23 citations
TL;DR: In this article, the stability of polytypic stacking sequences was shown to be dependent on the energy contribution from interactions between the constituent modules (layers) and the Axial Next-Nearest-Neighbour Ising (ANNNI) model was developed.
Abstract: The stability of long-period polytype stacking sequences can be shown to be dependent upon the energy contribution from interactions between the constituent modules (layers). Previous work has concentrated upon interactions between nearest and nextnearest (i.e. first and second) neighbour layers. It is shown that in some polytype systems, such as wollastonite, the equivalence of certain pairs of stacking sequences places constraints upon the allowed interactions between the modules. A mapping between these polytypic systems and a simple spin model, the Axial Next-Nearest-Neighbour Ising (ANNNI) model is developed in order to derive a theoretical phase diagram for these polytypes. The predictions of this phase diagram regarding the relative stability of polytype stacking sequences are shown to compare favourably with observations reported for natural mineral systems.
17 citations
TL;DR: In this paper, the stability of long-period commensurate phases in the presence of quenched impurities is studied. But the effect of impurity concentration on spin glass-like phases is not investigated.
Abstract: Domain-wall arguments are used to study the stability of long-period commensurate phases in the presence of quenched impurities. It is found that in three dimensions phases with periodicity larger than a critical value lc approximately 1/c, where c is the impurity concentration, are unstable. This results in disordered 'spin glass'-like phases. The effect can be studied experimentally by varying the impurity concentration in modulated systems.
10 citations
TL;DR: In this article, the condition necessary for the Harris criteria to be valid on hierarchical lattices was discussed, and it was shown that disorder is always relevant when the specific heat exponent, alpha p, is positive and showed how to construct lattices for which disorder becomes relevant while alpha p is still negative.
Abstract: The authors discuss the condition necessary for the Harris criteria to be valid on hierarchical lattices. They prove that disorder is always relevant when the specific heat exponent, alpha p, is positive and show how to construct lattices for which disorder becomes relevant while alpha p is still negative.
10 citations
TL;DR: In this article, the authors used domain arguments to study the behaviour of a sequence of long-period commensurate phases in the presence of quenched randomness, and found that the phases were stable for dimensions d>or=3.
Abstract: The authors use domain arguments to study the behaviour of a sequence of long-period commensurate phases in the presence of quenched randomness. The phases are found to be stable for dimensions d>or=3. For 2
10 citations
TL;DR: In this article, the effect of adding annealed vacancies to systems which exhibit long-period modulated phases in one space direction was investigated, and the results were relevant to the behaviour of polytypic substances and thiourea.
Abstract: The authors investigate the effect of adding annealed vacancies to systems which exhibit long-period modulated phases in one space direction. Concentration waves are formed which mirror the ordering of the underlying lattice. They expect the results to be relevant to the behaviour of polytypic substances and thiourea.
01 Jan 1985
TL;DR: An exhaustive count of all possible perovskite-like ABX4 phases, with the assumption that the only occurring symmetry-reducing operation is the tilting of regular BX 6 octahedra, is performed in this paper.
Abstract: An exhaustive count is performed of all possible perovskite-like ABX4 phases, with the assumption that the only occurring symmetry-reducing operation is the tilting of regular BX 6 octahedra. Each structure is schematically represented and is fully determined by its structure symbol, the space group and the diffraction features, which are condensed in a powerful shorthand notation: the 'diffraction typology'. Attention is paid to the displacement of the A cation and the resulting antiferroelectricity. The interrelations between the structures are presented in the * Work performed under the auspices of association SCKRUCA and with financial help from IIKW. t Also at: SCK/CEN, B-2400 Mol, Belgium. 'family tree' formalism in order to provide insight concerning the group-to-subgroup relations as a helpful tool in the prediction of phase transitions.