Phase inversion in two-phase solid systems driven by an elastic modulus mismatch

We have used phase field simulations to study elastic stress-driven phase inversion in which an initial microstructure with a minority phase embedded in a majority phase evolves to one in which the latter becomes embedded in the former. Such phase inversion is possible if the majority phase is elastically stiffer than the minority phase. For a given set of parameters (volume fraction and elastic moduli of the phases), phase inversion occurs at a characteristic microstructural length-scale (? ^c ). Our results show that ? ^c is lower for systems with larger mismatch in elastic moduli, and (to a smaller extent) in those with greater elastic anisotropy.     

Magnetic ordering in semiconducting Tl0.53K0.47Fe1.64Se2 single crystals studied by M?ssbauer spectroscopy

The results of a 57Fe M?ssbauer spectroscopy study between 4.5 and 523.2 K and in external magnetic fields (up to 90 kOe) of semiconducting Tl0.53K0.47Fe1.64Se2 single crystals are reported. Evidence is provided for a possible phase separation into the magnetic majority and minority phases. It is demonstrated that the magnetic moments of the divalent Fe atoms located at the 16i site (space group I4/m) of the majority phase and of the minority phase are antiferromagnetically ordered, with the Néel temperature T(N) = 518.0(3.6) K. The magnetic moments at 5.0 K of 2.09(1) and 2.28(2) μ(B) in these two phases are tilted from the crystallographic c axis by 18(1)° and 32(2)°, respectively. The Debye temperature of Tl0.53K0.47Fe1.64Se2 is found to be 228(4) K.     

The influence of a minority magnetic phase on the field dependence of the magnetocaloric effect

The field dependence of the magnetic entropy change can be used to detect the existence of a minority magnetic phase without experimentally reaching its Curie temperature. In this work, we present results that could suggest a breakdown of the recently proposed universal behaviour of the magnetocaloric effect in materials with a second-order magnetic phase transition in some La-containing samples. The behaviour of the outlier La-containing materials is an evidence of the existence of minority phases, preventing the construction of the universal curve with a single reference temperature. However, the use of two reference temperatures avoids this difficulty and allows applying the universal curve for practical purposes even with the presence of the minority phase.     

Dynamics of bimodal growth in pentacene thin films

Previous studies have established that pentacene films deposited on silicon oxide consist of a substrate-induced "thin-film" phase, with the bulk phase of pentacene detected in thicker films only. We show that the bulk phase nucleates as early as the first monolayer, and continues to nucleate as film growth progresses, shadowing the growth of the thin-film phase. Moreover, we find that the transition between the "thin-film" and the bulk phase is not a continuous one, as observed in heteroepitaxial systems, but rather the two phases nucleate and grow independently.     

Detecting phase synchronization in noisy systems

A quantitative method for automatic detection of phase synchronization in noisy experimental bivariate time series is proposed, based on the fact that instantaneous phases of phase-synchronized (sub) systems are mutually dependent in a specific way irrespective of a relation between the original time series. The level of dependence between the instantaneous phases is quantified by a statistical dependence parameter, which also reflects the strength of the systems' phase synchronization. Ranges of the parameter values, for which the detection of the phase synchronization can be considered reliable, are estimated by using the technique of surrogate data. Possible applications of the proposed method are demonstrated by using both numerically generated and real experimental data, namely solutions of two coupled Rössler systems, mammalian cardio-respiratory data, and long-term recordings of surface atmospheric temperature and sunspot numbers.     

A density-functional theory study of microphase formation in binary Gaussian mixtures

We use density-functional theory to study the formation of inhomogeneous phases in a binary mixture of particles interacting by repulsive, athermal Gaussian potentials with suitably chosen strengths and ranges. Both the potential parameters and the free-energy functional are the same as those adopted in a previous investigation by other authors (Archer A J, Likos C N and Evans R 2004 J. Phys.: Condens. Matter 16 L297), but here a fully numerical minimization of the functional is performed, without any assumption about the functional form of the density profile. We find lamellar, rod and cluster phases. In the lamellar phase, the two species arrange into intercalating stripes; in the rod and cluster phases, the minority species is localized at the site of a periodic lattice, either triangular (for rods) or body-centred cubic (for clusters), while the other species is distributed non-uniformly in the remaining region, so that it forms a percolating network. The order of the transition from the homogeneous to the inhomogeneous phase and the phase diagram of the mixture are also discussed.     

偏晶合金液-液相分离的格子玻尔兹曼方法模拟

本文建立了一个模拟在弥散相液滴的扩散长大、碰撞凝并和Ostwald熟化等因素的作用下偏晶合金液-液相分离过程的二维格子玻尔兹曼方法 (lattice Boltzmann method, LBM) 模型.该模型结合了Shan-Chen的两相流模型和Qin的介观粒子相互作用势模型的优点,并在LB演化方程中引入了反映相变的源项.应用该模型模拟研究了偏晶合金液-液相分离过程中单液滴的生长、两液滴的合并和多液滴的生长规律.结果表明在两液相区中第二相单个液滴的生长是一个通过扩散从非平衡态到平衡态过渡的过程.两液滴合并 关键词： 偏晶合金 液-液相分离 格子玻尔兹曼方法     

Boundary-driven phase transitions in open driven systems with an umbilic point

Different phases in open driven systems are governed by either shocks or rarefaction waves. A presence of an isolated umbilic point in bidirectional systems of interacting particles stabilizes an unusual large scale excitation, an umbilic shock (U-shock). We show that in open systems the U-shock governs a large portion of phase space, and drives a new discontinuous transition between the two rarefaction-controlled phases. This is in contrast to strictly hyperbolic case where such a transition is always continuous. Also, we describe another robust phase which takes place at the phase governed by the U-shock, if the umbilic point is not isolated.     

Thermodynamics of binary solutions of the eutectic type with intermediate phases of constant composition

A consistent method is proposed for calculating the phase diagrams of binary solutions with intermediate phases of constant composition. The proposed method is based on the nonlinear transformations of the concentration axes and makes it possible to correctly reduce the calculation of the phase diagrams with intermediate phases to a sequence of phase diagrams of individual subsystems. The thermodynamics of binary solutions of the eutectic type with intermediate phases of constant composition is described using the proposed method within the framework of the generalized lattice model. The results of the calculations performed are compared with a number of phase diagrams of real binary systems.     

Masking by harmonic complexes in budgerigars (Melopsittacus undulatus)

In humans, masking by harmonic complexes is dependent not only on the frequency content of the masker, but also its phase spectrum. Complexes that have highly modulated temporal waveforms due to the selection of their component phases usually provide less masking than those with flatter temporal envelopes. Moreover, harmonic complexes that are created with negative Schroeder phases (component phases monotonically decreasing with increasing harmonic frequency) may provide more masking than those created with positive Schroeder phases (monotonically increasing phase), even though both temporal envelopes are equally flat. To date, there has been little comparative work on the masking effectiveness of harmonic complexes. Using operant conditioning and the method of constant stimuli, masking of pure tones by harmonic complexes was examined in budgerigars at several different masker levels for complexes constructed with two different fundamental frequencies. In contrast to humans, thresholds in budgerigars differed very little for the two Schroeder-phase waveforms. Moreover, when there was a difference in masking by these two waveforms, the positive Schroeder was the more effective masker--the reverse of that described for humans. Control experiments showed that phase selection was relevant to the masking ability of harmonic complexes in budgerigars. Release from masking occurred when the components were in coherent phase, compared with a complex with random phases selected for each component. It is suggested that these psychoacoustic differences may emerge from structural and functional differences between the avian and mammalian peripheral auditory systems involving traveling wave mechanics and spectral tuning characteristics.     

Induced P-wave superfluidity in asymmetric fermi gases

We show that two new intraspecies P-wave superfluid phases appear in two-component asymmetric Fermi systems with short-range S-wave interactions. In the BEC limit, phonons of the molecular BEC induce P-wave superfluidity in the excess fermions. In the BCS limit, density fluctuations induce P-wave superfluidity in both the majority and the minority species. These phases may be realized in experiments with spin-polarized Fermi gases.     

Phase-Modulated 2D Topological Physics in a One-Dimensional Ultracold System

We propose a one-dimensional optical lattice model to simulate and explore two-dimensional topological phases with ultracold atoms,considering the phases of the hopping strengths as an extra dimension.It is shown that the model exhibits nontrivial phases,and corresponding two chiral-edge states.Moreover,we demonstrate the connections between changes in the topological invariants and the Dirac points.Furthermore,the topological order detected by the particle pumping approach in cold atoms is also investigated.The results obtained here provide a feasible and flexible method of simulating and exploring high-dimensional topological phases in lowdimension systems via the controllable phase of the hopping strength.     

Fluid-fluid demixing of off-critical colloid-polymer systems confined between parallel plates

We investigate the off-critical demixing of colloid-polymer systems confined between two parallel plates, where the surface potential is short ranged. We study the case where the minority phase completely wets the surfaces. We find that initially the sample separates as in bulk, until the size of the domains becomes sufficiently large such that further growth is restricted by the plate spacing. The behaviour of the droplets is then determined by the wettability of the walls. We furthermore explore a sample where the loss of wetting phase material to the surfaces causes a shift from a morphology associated with an unstable sample, showing spinodal decomposition, to that associated with a metastable sample. This underlines the importance of the rich interplay between the viscosity contrast and the local volume fraction on the observed morphologies.     

Phase separation in one-dimensional hard-core boson system with two- and three-body interactions

We investigate the ground state phase diagram of hard-core boson system with repulsive two-body and attractive three-body interactions in one-dimensional optical lattice. When these two interactions are comparable and increasing the hopping rate, physically intuitive analysis indicates that there exists a phase separation region between the solid phase with charge density wave order and superfluid phase. We identify these phases and phase transitions by numerically analyzing the density distribution, structure factor of density-density correlation function, three-body correlation function and von Neumann entropy estimator obtained by density matrix renormalization group method. These phases and phase transitions are expected to be observed in the ultra-cold polar molecule experiments by properly tuning interaction parameters as suggested in Methods by Büchler et al. [Nat. Phys. 3, 726 (2007)], which is constructive to understand the physics of ubiquitous insulating-superconducting phase transitions in condensed matter systems.     

Phase-field model for multiphase systems with different thermodynamic factors

A modified phase-field model for quantitative simulations of low-speed phase transitions in multiphase systems is proposed, which takes into account the difference between thermodynamic factors in all the phases. The presented model is based on the quantitative phase-field concept developed by Steinbach et al. [I. Steinbach, F. Pezolla, B. Nestler, M. Seeelberg, R. Prieler, G.J. Schmitz, J.L.L. Rezende, A phase field concept for multiphase systems, Physica D 94 (1996) 135] for multiphase systems allowing to consider the multiphase transition as a superposition of pairwise interactions between two phases. We complete this approach and develop a model, which uses parameters derived from chemical free energy functions of individual phases evaluated from experimental data by the CALPHAD method Lukas et al. (2007) [17]. Because the thermodynamic factors are different in various phases we need to evaluate a special form of total chemical free energy function of a multiphase mixture and use it in the phase-field model. It is shown, that for the developed model the thin-interface asymptotic and the anti-trapping term developed previously for the solidification of pure substances can be applied. The model is verified by an example of the Al-Ni system whose peritectic structural morphology during the directional solidification is investigated. The suggested model can be also extended to multicomponent systems.     

Fast resistive reconnection regime in the nonlinear evolution of double tearing modes

Phases of nonlinear double tearing modes are studied numerically. The first two phases lead to the formation and growth of magnetic islands and are followed by a fast reconnection phase to complete the process, driven by a process of neighboring magnetic separatrices merging and magnetic islands coupling. The fast growth can be understood as a result of the island interaction equivalent to a steadily inward flux boundary driven. Resistivity dependences for various phases are studied and shown by scaling analysis for the first time. It is found that after an early Sweet-Parker phase with a eta(1/2)-scale, a slow nonlinear phase in a Rutherford regime with a eta(1)-scale is followed by the fast reconnection phase with a eta(1/5)-scale.     

Quantum phase transitions in matrix product states of one-dimensional spin-1 chains

We present a new model of quantum phase transitions in matrix product systems of one-dimensional spin-1 chains and study the phases coexistence phenomenon. We find that in the thermodynamic limit the proposed system has three different quantum phases and by adjusting the control parameters we are able to realize any phase, any two phases equal coexistence and the three phases equal coexistence. At every critical point the physical quantities including the entanglement are not discontinuous and the matrix product system has long-range correlation and N-spin maximal entanglement. We believe that our work is helpful for having a comprehensive understanding of quantum phase transitions in matrix product states of one-dimensional spin chains and of certain directive significance to the preparation and control of one-dimensional spin lattice models with stable coherence and N-spin maximal entanglement.     

Shifted-phase calibration for a 3-D shape measurement system based on orthogonal composite grating projection

This paper proposes a novel method for reducing measurement error caused by spectrum overlapping in orthogonal-composite-grating-based 3-D measurement method. For 3-D measurement systems based on orthogonal composite grating projection, spectrum overlapping causes phase of each deformed phase-shifting fringe changed differently, which violates the principle that the shifted phases between adjacent deformed fringes must be equivalent to 2π/3, and therefore results in phase measurement error. The proposed shifted-phase calibration method is based on that phase variation of each deformed fringe is independent of height and reflectivity of the measured object. Three composite gratings are projected on the reference plane, and each carrier channel includes three phase-shifting gratings needed in phase measuring profilometry (PMP). Because the adjacent phase-shifting fringes demodulated from the same carrier channel have the phase difference of 2π/3, we can respectively calculate the reference plane's phases of three carrier channels by the phase algorithm of PMP method, and the shifted phases between them are obtained. When an object is measured, the shifted phases between deformed phase-shifting fringes can be calibrated. A new 3-D measurement mathematical model is set to reconstruct object. Our experiments prove that the proposed method can effectively restrain the effect of spectrum overlapping and improve measurement accuracy almost one times.     

Effective history length of the minority game

It is known that the memory is relevant in the symmetric phase of the minority game. In our previous work we have successfully explained the quasi-periodic behavior of the game in the symmetric phase with the help of the probability theory. Based on this explanation, we are able to determine how the history length affects the variance of the system in this paper. By using some particular types of fake history such as periodic type and random type, we determine how efficient the history length has been used in the standard game. Furthermore, the analysis on the effective history length strongly supports the result we proposed previously that there are three distinct phases in the minority game.     

Formation and structural phase transition in Co atomic chains on a Cu(775) surface

The formation of Co atomic chains on a Cu(775) surface is investigated by the kinetic Monte Carlo method. It is found that the length of Co atomic chains formed as a result of self-organization during epitaxial growth is a random quantity and its mean value depends on the parameters of the experiment. The existence of two structural phases in atomic chains is detected using the density functional theory. In the first phase, the separations between an atom and its two nearest neighbors in a chain are 0.230 and 0.280 nm. In the second phase, an atomic chain has identical atomic spacings of 0.255 nm. It is shown that the temperature of the structural phase transition depends on the length of the atomic chain.