56 research outputs found
Nonequilibrium evolution thermodynamics
A new approach - nonequilibrium evolution thermodynamics, is compared with
classical variant of Landau approachComment: 4 pages, 1 figur
Thermodynamics and kinetics of solids fragmentation at severe plastic deformation
The approach of nonequilibrium evolution thermodynamics earlier offered is
developed. It helps to describe the processes of defect formation within the
adiabatic approximation. The basic equations system depends on the initial
defects distribution (dislocations and grain boundaries). The phase diagram is
determined with the domains of the realization of different limiting structure
types. The interaction effect of several defect types on the formation of a
limiting structure is investigated in terms of the internal energy. The
conditions of the formation of two limiting structures are found. The kinetics
of the steady-state values establishment of the defects density is investigated
within the scope of the adiabatic approximation. The dislocations density
change follows the evolution of the grain boundaries density in this approach.
It is shown that grain sizes, in limiting structures, decrease with an increase
of the elastic strains.Comment: 14 pages, 6 figure
Realistic interatomic potential for MD simulations
The coefficients of interatomic potential of simple form Exp-6 for neon are
obtained. Repulsive part is calculated ab-initio in the Hartree-Fock
approximation using the basis of atomic orbitals orthogonalized exactly on
different lattice sites. Attractive part is determined empirically using single
fitting parameter. The potential obtained describes well the equation of state
and elastic moduli of neon crystal in wide range of interatomic distances and
it is appropriate for molecular dynamic simulations of high temperature
properties and phenomena in crystals and liquids.Comment: MikTex v.2.1 (AMS-TEX),11 pages, 3 EPS figure
Formation of the internal structure of solids under severe action
On the example of a particular problem, the theory of vacancies, a new form
of kinetic equations symmetrically incorporation the internal and free energies
has been derived. The dynamical nature of irreversible phenomena at formation
and motion of defects (dislocations) has been analyzed by a computer
experiment. The obtained particular results are extended into a thermodynamic
identity involving the law of conservation of energy at interaction with an
environment (the 1st law of thermodynamics) and the law of energy
transformation into internal degree of freedom (relaxation). The identity is
compared with the analogous Jarzynski identity. The approach is illustrated by
simulation of processes during severe plastic deformation, the Rybin kinetic
equation for this case has been derived.Comment: 9 pages, 5 figure
Superparamagnetic magnetization equation in two dimensions
An equation for the dependence of magnetization on magnetic field in the case of two-dimensional (base plane) anisotropy has been derived. The resulting equation is expressed as an infinite series of modified Bessel functions, unlike the elementary function expressions that are applicable to the one-dimensional (axially anisotropic) and three-dimensional (isotropic) cases. Nevertheless, in the low-field limit, the series can be effectively truncated to give an approximate solution, while, in the high-field limit, an alternative expression has been derived which represents the limiting function as the field strength tends to infinity. The resulting expressions can be used to describe the superparamagnetic magnetization and susceptibility as a function of magnetic field in situations where the magnetic moments are constrained to lie in a plane, with no preferred direction within the plane. This can therefore be applied to two-dimensional structures, such as magnetic thin films, where magnetostatic energy confines the moments to the plane of the film, or to three-dimensional structures with planar magnetocrystalline anisotropy
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