Search results for "Phase diagram"
showing 10 items of 346 documents
Quasiparticles and quantum phase transition in universal low-temperature properties of heavy-fermion metals
2006
We demonstrate, that the main universal features of the low temperature experimental $H-T$ phase diagram of CeCoIn5 and other heavy-fermion metals can be well explained using Landau paradigm of quasiparticles. The main point of our theory is that above quasiparticles form so-called fermion-condensate state, achieved by a fermion condensation quantum phase transition (FCQPT). When a heavy fermion liquid undergoes FCQPT, the fluctuations accompanying above quantum critical point are strongly suppressed and cannot destroy the quasiparticles. The comparison of our theoretical results with experimental data on CeCoIn5 have shown that the electronic system of above substance provides a unique opp…
Comment on “Accurate ground-state phase diagram of the one-dimensional extended Hubbard model at half filling”
2004
In PRB 68, 153101 (2003), Guoping Zhang presented density-matrix renormalization group (DMRG) results which contradict my DMRG calculations and Hirsch's quantum Monte Carlo (QMC) simulations for the charge-density-wave (CDW) phase boundary in the one-dimensional extended Hubbard model at half filling. In this Comment I show that Zhang's results are inaccurate and that his criticism of my work is groundless.
Quantum Phases in a Resonantly Interacting Boson-Fermion Mixture
2005
We consider a resonantly-interacting Bose-Fermi mixture of $^{40}$K and $^{87}$Rb atoms in an optical lattice. We show that by using a red-detuned optical lattice the mixture can be accurately described by a generalized Hubbard model for $^{40}$K and $^{87}$Rb atoms, and $^{40}$K-$^{87}$Rb molecules. The microscopic parameters of this model are fully determined by the details of the optical lattice and the interspecies Feshbach resonance in the absence of the lattice. We predict a quantum phase transition to occur in this system already at low atomic filling fraction, and present the phase diagram as a function of the temperature and the applied magnetic field.
Simulation of Transport in Partially Miscible Binary Fluids: Combination of Semigrandcanonical Monte Carlo and Molecular Dynamics Methods
2004
Binary Fluids that exhibit a miscibility gap are ubiquitous in nature (glass melts, polymer solutions and blends, mixtures of molten metals, etc.) and exhibit a delicate interplay between static and dynamic properties. This is exemplified for a simple model system, the symmetrical AB Lennard-Jones mixture. It is shown how semigrandcanonical Monte Carlo methods, that include A→B (B→A) identity switches as Monte Carlo moves, can yield the phase diagram, the interfacial tension between coexisting phases, and various pair correlation functions and structure factors. In addition to the build-up of long-ranged concentration correlations near the critical point, unmixing is also accompanied by the…
Core-melted clusters
1999
The possibility of the existence of a core-melted cluster is investigated. To this end, a pair potential is introduced, with the property that the solid state of the cluster is less dense than the liquid state. With this kind of potential, the cluster exhibits a quite unusual behavior. In addition to the known states, solid, liquid, and surface-melted, it can also be found in a “dense-liquid” phase (a disordered state appearing at low temperatures), a “core-melted” phase, and a “core-surface-melted” phase. In the core-melted phase, the external part of the cluster consists of atoms that are vibrating around regular crystalline sites, while the core atoms have much bigger mobility, sometimes…
Monte Carlo Simulation of Langmuir Monolayer Models
1998
We study a coarse grained, continuum model for Langmuir monolayers, i.e., monolayers of amphiphilic molecules on a polar substrate. The amphiphiles are represented by stiff chains of beads with one end grafted to a planar surface. Monte Carlo Simulations at constant pressure have been performed, using simulation boxes of variable size and variable shape. A number of techniques have been explored in order to obtain an efficient simulation algorithm. We discuss the resulting phase diagram, characterize the different phases, and analyze the conditions, under which they can be found.
Spinodal decomposition of polymer solutions: molecular dynamics simulations of the two-dimensional case.
2012
As a generic model system for phase separation in polymer solutions, a coarse-grained model for hexadecane/carbon dioxide mixtures has been studied in two-dimensional geometry. Both the phase diagram in equilibrium (obtained from a finite size scaling analysis of Monte Carlo data) and the kinetics of state changes caused by pressure jumps (studied by large scale molecular dynamics simulations) are presented. The results are compared to previous work where the same model was studied in three-dimensional geometry and under confinement in slit geometry. For deep quenches the characteristic length scale ℓ(t) of the formed domains grows with time t according to a power law close to [Formula: see…
Structure and Thermodynamics of Binary Mixtures (Solutions)
2014
The concepts of chapter 2 are generalized to binary liquid mixtures (solutions). With the help of the concept of number and concentration fluctuations contact to the thermodynamics of solutions and physical chemistry of solutions is made. The perturbative RPA is shown to be equivalent to Flory’s theory of regular solutions. The phase diagrams of regular solutions and metal-salt solutions are discussed and explained in terms of the theories.
How do droplets on a surface depend on the system size?
2002
Abstract We investigate the thermodynamics of inhomogeneous polymer melts in the framework of a coarse grained off-lattice model. Properties of the liquid–vapour interface and the packing of the melt in contact with an attractive wall are considered. We employ Monte Carlo simulations in the grand canonical ensemble to determine excess free energies, the wetting temperature and the pre-wetting line, as well as the pre-wetting critical point. Having determined the wetting properties and the phase diagram of the model polymer, we perform canonical Monte Carlo simulations of small droplets on a surface. This allows us to study the dependence of droplet size on the wetting properties. It is foun…
Spinodal Decomposition Kinetics of Colloid-Polymer Mixtures Including Hydrodynamic Interactions
2012
The phase separation dynamics of a model colloid-polymer mixture is studied by taking explicitly the hydrodynamic interactions caused by the solvent into account. Based on the studies on equilibrium phase behavior we perform a volume quench from the homogeneous region of the phase diagram deep into the region where colloid-rich and polymer-rich phases coexist. We demonstrate that the Multiparticle Collision Dynamics (MPCD) algorithm is well suited to study spinodal decomposition and present first results on the domain growth behavior of colloid-polymer mixtures in quasi two-dimensional confinement. On the one hand side we find that the boundary condition of the solvent with respect to the r…