共查询到20条相似文献,搜索用时 31 毫秒
1.
D. Loison K.D. Schotte 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,5(3):735-743
The nature of the phase transition for the XY stacked triangular antiferromagnet (STA) is a controversial subject at present. The field theoretical renormalization group
(RG) in three dimensions predicts a first order transition. This prediction disagrees with Monte-Carlo (MC) simulations which
favor a new universality class or a tricritical transition. We simulate by the Monte-Carlo method two models derived from
the STA by imposing the constraint of local rigidity which should have the same critical behavior as the original model. A
strong first order transition is found. Following Zumbach we analyze the second order transition observed in MC studies as
due to a fixed point in the complex plane. We review the experimental results in order to clarify the critical behavior observed.
Received: 18 February 1998 / Revised: 24 April 1998 / Accepted: 30 April 1998 相似文献
2.
D. Loison 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):517-521
We study the phase transition in generalized chiral or Stiefel's models using Monte Carlo simulations. These models are characterized
by a breakdown of symmetry O(N)/O(N-P). We show that the phase transition is clearly first order for when P=N and P=N-1, contrary to predictions based on the renormalization group in expansion but in agreement with a recent non perturbative renormalization group approach.
Received 7 October 1999 相似文献
3.
P.G. Dommersnes J.-B. Fournier 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(1):9-12
We study the collective behavior of inclusions inducing local anisotropic curvatures in a flexible fluid membrane. The N-body interaction energy for general anisotropic inclusions is calculated explicitly, including multi-body interactions. Long-range
attractive interactions between inclusions are found to be sufficiently strong to induce aggregation. Monte Carlo simulations
show a transition from compact clusters to aggregation on lines or circles. These results might be relevant to proteins in
biological membranes or colloidal particles bound to surfactant membranes.
Received 30 July 1999 and Received in final form 8 September 1999 相似文献
4.
The freezing transition of a network model for tensionless membranes confined to two dimensions is investigated by Monte Carlo
simulations and scaling arguments. In this model, a freezing transition is induced by reducing the tether length. Translational
and bond-orientational order parameters and elastic constants are determined as a function of the tether length. A finite-size
scaling analysis is used to show that the crystal melts via successive dislocation and disclination unbinding transitions, in qualitative agreement with the predictions of the Kosterlitz-Thouless-Halperin-Nelson-Young
theory. The hexatic phase is found to be stable over only a very small interval of tether lengths.
Received 4 June 1999 and Revised in final form 1 September 1999 相似文献
5.
T. Müller W. Selke 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):549-553
Using kinetic Monte Carlo simulations and a bond-counting ansatz, thermal stability and diffusion of an adatom island on a
crystal surface are studied. At low temperatures, the diffusion constant D is found to decrease for a wide range of island sizes like , where is close to one, N being the number of adatoms in the cluster. By heating up the surface, the system undergoes a phase transition above which
the island disappears. Characteristics of that transition are discussed.
Received 20 January 1999 相似文献
6.
T. Garel H. Orland E. Orlandini 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):261-268
We consider polymers made of magnetic monomers (Ising or Heisenberg-like) in a good solvent. These polymers are modeled as
self-avoiding walks on a cubic lattice, and the ferromagnetic interaction between the spins carried by the monomers is short-ranged
in space. At low temperature, these polymers undergo a magnetic induced first order collapse transition, that we study at
the mean field level. Contrasting with an ordinary point, there is a strong jump in the polymer density, as well as in its magnetization. In the presence of a magnetic field,
the collapse temperature increases, while the discontinuities decrease. Beyond a multicritical point, the transition becomes
second order and -like. Monte Carlo simulations for the Ising case are in qualitative agreement with these results.
Received 11 February 1999 相似文献
7.
E.L. Præstgaard B. Schmittmann R.K.P. Zia 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(4):675-695
We investigate the collective behavior of an Ising lattice gas, driven to non-equilibrium steady states by being coupled to
two thermal baths. Monte Carlo methods are applied to a two-dimensional system in which one of the baths is fixed at infinite
temperature. Both generic long range correlations in the disordered state and critical properties near the second order transition
are measured. Anisotropic scaling, a key feature near criticality, is used to extract and some critical exponents. On the theoretical front, a continuum theory, in the spirit of Landau-Ginzburg, is presented.
Being a renormalizable theory, its predictions can be computed by standard methods of -expansions and found to be consistent with simulation data. In particular, the critical behavior of this system belongs to
a universality class which is quite different from the uniformly driven Ising model.
Received 4 October 2000 相似文献
8.
M. Pleimling 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,10(3):465-473
The properties of S = 1 anisotropic Heisenberg models with nondiagonal exchange between axial and planar spin components are investigated using
Monte Carlo techniques. The quantum nature is taken into account in a semi-classical approximation. The ordering of the spins
when applying an external field with axial and planar components is discussed. It is argued that the quantum nature of the
spins and the nondiagonal exchange may explain the peculiar shape of the magnetic specific heat of FeBr2 as well as the weakly first-order phase transition observed in the same compound when a tilted field is applied.
Received 24 January 1999 相似文献
9.
G. Biroli R. Monasson M. Weigt 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(3):551-568
A variational approach to finite connectivity spin-glass-like models is developed and applied to describe the structure of
optimal solutions in random satisfiability problems. Our variational scheme accurately reproduces the known replica symmetric
results and also allows for the inclusion of replica symmetry breaking effects. For the 3-SAT problem, we find two transitions
as the ratio of logical clauses per Boolean variables increases. At the first one , a non-trivial organization of the solution space in geometrically separated clusters emerges. The multiplicity of these
clusters as well as the typical distances between different solutions are calculated. At the second threshold , satisfying assignments disappear and a finite fraction of variables are overconstrained and take the same values in all optimal (though unsatisfying) assignments. These values
have to be compared to , obtained from numerical experiments on small instances. Within the present variational approach, the SAT-UNSAT transition
naturally appears as a mixture of a first and a second order transition. For the mixed 2+p-SAT with p<2/5, the behavior is as expected much simpler: a unique smooth transition from SAT to UNSAT takes place at .
Received 12 July 1999 相似文献
10.
A.O. Sorokin 《Physics letters. A》2018,382(48):3455-3462
Critical behavior of three-dimensional classical frustrated antiferromagnets with a collinear spin ordering and with an additional twofold degeneracy of the ground state is studied. We consider two lattice models, whose continuous limit describes a single phase transition with a symmetry class differing from the class of non-frustrated magnets as well as from the classes of magnets with non-collinear spin ordering. A symmetry breaking is described by a pair of independent order parameters, which are similar to order parameters of the Ising and O(N) models correspondingly. Using the renormalization group method, it is shown that a transition is of first order for non-Ising spins. For Ising spins, a second order phase transition from the universality class of the O(2) model may be observed. The lattice models are considered by Monte Carlo simulations based on the Wang–Landau algorithm. The models are a ferromagnet on a body-centered cubic lattice with the additional antiferromagnetic exchange interaction between next-nearest-neighbor spins and an antiferromagnet on a simple cubic lattice with the additional interaction in layers. We consider the cases N = 1, 2, 3 and in all of them find a first-order transition. For the N = 1 case we exclude possibilities of the second order or pseudo-first order of a transition. An almost second order transition for large N is also discussed. 相似文献
11.
G. Palágyi C. Chatelain B. Berche F. Iglói 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(2):357-367
Using extensive Monte Carlo simulations, transfer matrix techniques and conformal invariance, ferromagnetic random q-state Potts models for are studied in the vicinity of the critical temperature. In particular the surface and bulk magnetization exponents and are found monotonically increasing with q. At the critical temperature, different moments (n) of the magnetization profiles are calculated which are all found to accurately follow predictions of conformal invariance.
The critical correlation functions show multifractal behaviour, the decay exponents of the different moments both in the volume
and at the surface, are n-dependent.
Received 4 June 1999 相似文献
12.
X.S. Chen V. Dohm D. Stauffer 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,14(4):699-704
Using field theory and Monte Carlo (MC) simulation we investigate the finite-size effects of the magnetization M for the three-dimensional Ising model in a finite cubic geometry with periodic boundary conditions. The field theory with
infinite cutoff gives a scaling form of the equation of state where is the reduced temperature, h is the external field and L is the size of system. Below and at the theory predicts a nonmonotonic dependence of f(x,y) with respect to at fixed and a crossover from nonmonotonic to monotonic behaviour when y is further increased. These results are confirmed by MC simulation. The scaling function f(x,y) obtained from the field theory is in good quantitative agreement with the finite-size MC data. Good agreement is also found
for the bulk value at .
Received 20 July 1999 and Received in final form 11 November 1999 相似文献
13.
R.M.C. de Almeida N. Lemke I.A. Campbell 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,18(3):513-518
We study random walks on the dilute hypercube using an exact enumeration Master equation technique, which is much more efficient
than Monte Carlo methods for this problem. For each dilution p the form of the relaxation of the memory function q(t) can be accurately parametrized by a stretched exponential over several orders of magnitude in q(t). As the critical dilution for percolation is approached, the time constant tends to diverge and the stretching exponent drops towards 1/3. As the same pattern of relaxation is observed in a wide class of glass formers, the fractal like morphology
of the giant cluster in the dilute hypercube appears to be a good representation of the coarse grained phase space in these
systems. For these glass formers the glass transition may be pictured as a percolation transition in phase space.
Received 16 June 2000 and Received in final form 13 October 2000 相似文献
14.
J.C. Ewert G. Schmitz 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,17(3):391-403
A study of the reordering kinetics of ion-irradiated Ni3Al is presented. The development of long-range order during annealing treatments is measured by quantitative electron diffractometry.
According to the temperature dependence of the observed kinetics, the reaction is dominated by non-equilibrium vacancies.
As a consequence, the kinetics can be calibrated versus the absolute number of atomic jumps necessary to establish the observed degree of order. In order to analyse the experimental
data, Monte Carlo simulations are performed. It is shown that, beside the temperature dependence of the driving force, the
ordering efficiency of the vacancy jumps itself is temperature dependent due to different mobilities of the atomic species.
Received 6 December 1999 and Received in final form 23 June 2000 相似文献
15.
F.W.S. Lima J.E. Moreira J.S. Andrade Jr. U.M.S. Costa 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,13(1):107-110
We investigate the two-dimensional eight-states ferromagnetic Potts model in the Voronoi-Delaunay tessellation. In this study,
we assume that the coupling factor J varies with the distance r between the first neighbors as , with . The disordered system is simulated applying the single-cluster Monte-Carlo update algorithm and the reweighting technique.
We find that this model displays a first-order phase transition if , in agreement with previous recent studies. For and 1.0, a typical second order transition is observed and the critical exponents for magnetization and susceptibility are
calculated.
Received 19 May 1999 and Received in final form 2 June 1999 相似文献
16.
P. Sen S. Dasgupta D. Stauffer 《The European Physical Journal B - Condensed Matter and Complex Systems》1998,1(1):107-110
The dynamical critical exponent z of the Ising antiferromagnet under the constraint of a fixed zero magnetization is verified by Monte Carlo simulations to
be compatible with that of the usual Glauber dynamics of model A, while for positive magnetization the exponent seems different.
We also determine the diffusivity of the magnetization and finite size effects.
Received: 18 June 1997 / Revised: 28 July 1997 / Accepted: 13 October 1997 相似文献
17.
Roger M Guenoun P Muller F Belloni L Delsanti M 《The European physical journal. E, Soft matter》2002,9(4):313-326
The concentration profiles of monomers and counterions in star-branched polyelectrolyte micelles are calculated through Monte
Carlo simulations, using the freely jointed chain model. We have investigated the onset of different regimes corresponding
to the spherical and Manning condensation of counterions as a function of the strength of the Coulomb coupling. The Monte
Carlo results are in fair agreement with the predictions of Self-Consistent-Field analytical models. We have simulated a real
system of diblock copolymer micelles of (sodium-polystyrene-sulfonate)(NaPSS)-(polyethylene-propylene)(PEP) with f = 54 hydrophilic branches of N = 251 monomers at room temperature in salt-free solution. The calculated form factor compares nicely with our neutron scattering
data.
Received 18 July 2002 and Received in final form 11 October 2002
RID="a"
ID="a"e-mail: roger@drecam.saclay.cea.fr 相似文献
18.
N.J. Mottram S.J. Elston 《The European Physical Journal B - Condensed Matter and Complex Systems》1999,12(2):277-284
We have theoretically investigated chevron formation in smectic C materials and the transformation of this chevron structure to a tilted layer structure as the cell is sheared. We find a
series of transition temperatures at which the behaviour of the cell critically changes. As the cell is cooled from the smectic
A phase past the first critical temperature there is a second order transition which forms two tilted layer states with lower energy than the smectic A bookshelf structure. Although these low energy tilted structures exist the bookshelf structure is the stable state for zero
shear. However, upon further cooling this bookshelf structure becomes unstable to the formation of a chevron state. Now when
the cell is sheared the chevron structure smoothly transforms into the tilted layer structure. As each further critical temperature
is passed an additional multiple chevron solution is formed which although a high energy, unstable state may be observed transiently. For sufficiently low
temperatures the transition from chevron to tilted layer becomes first order. This first order transition occurs as the chevron
interface merges with the surface alignment region to form the tilted layer structure.
Received 28 December 1998 and Received in final form 8 April 1999 相似文献
19.
A. Honecker M. Kaulke K.D. Schotte 《The European Physical Journal B - Condensed Matter and Complex Systems》2000,15(3):423-434
CsCuCl3 is a ferromagnetically stacked triangular spin-1/2 antiferromagnet. We discuss models for its zero-temperature magnetization
process. The models range from three antiferromagnetically coupled ferromagnetic chains to the full three-dimensional situation.
The situation with spin-1/2 is treated by expansions around the Ising limit and exact diagonalization. Further, weak-coupling
perturbation theory is used mainly for three coupled chains which are also investigated numerically using the density-matrix
renormalization group technique. We find that already the three-chain model gives rise to the plateau-like feature at one
third of the saturation magnetization which is observed in magnetization experiments on CsCuCl3 for a magnetic field perpendicular to the crystal axis. For a magnetic field parallel to the crystal axis, a jump is observed
in the experimental magnetization curve in the region of again about one third of the saturation magnetization. In contrast
to earlier spinwave computations, we do not find any evidence for such a jump with the model in the appropriate parameter
region.
Received 25 October 1999 and Received in final form 30 December 1999 相似文献
20.
M. Holtschneider W. Selke 《The European Physical Journal B - Condensed Matter and Complex Systems》2008,62(2):147-154
Classical uniaxially anisotropic Heisenberg and XY antiferromagnets
in a field along the easy axis on a square lattice
are analysed, applying ground state
considerations and Monte Carlo techniques. The models are known to
display antiferromagnetic and spin-flop phases. In the Heisenberg
case, a single-ion anisotropy is added to the XXZ antiferromagnet,
enhancing or competing with the uniaxial exchange anisotropy. Its
effect on the stability of non-collinear structures of biconical
type is studied. In the case of the anisotropic XY antiferromagnet,
the transition region between the antiferromagnetic and spin-flop
phases is found to be dominated by degenerate bidirectional
fluctuations. The phase diagram is observed to resemble closely
that of the XXZ antiferromagnet without single-ion anisotropy. 相似文献