75 research outputs found
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
Study of Photometric Variability of Selected SU UMa Dwarf Novae
In this work we present time-resolved photometry of several poorly-studied dwarf novae during recent superoutbursts. Observations were made with a CCD, mounted on 50- and 60-cm telescopes of the Sternberg Astronomical Institute in Crimea in April - May and October 2012 and June - July 2013. Superhumps were detected in light curves of all the dwarf novae. The amplitudes and periods of detected light variations were calculated. Superhumps evolution was also followed up for all systems and classification is improved
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
Nonlinear effects in memristors with mobile vacancies
Because the local concentration of vacancies in any material is bounded,
their motion must be accompanied by nonlinear effects. Here we look for such
effects in a simple model for electric field driven vacancy motion in
memristors, solving the corresponding nonlinear Burgers' equation with
impermeable nonlinear boundary conditions analytically. We find non-monotonous
relaxation of the resistance while switching between the stable
(``on''/``off'') states of the memristor; and qualitatively different film
thickness dependencies of switching time (under applied current) and relaxation
time (under no current). Our exact solution can serve as a useful benchmark for
simulations of more complex memristor models.Comment: 5 pages, 3 figures (v2: clarifications/improvements as per referee
comments and other minor changes
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
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