194 research outputs found
Density of states of the 2D system of the soft--sphere fermions by the path integral Monte Carlo simulations
The Wigner formulation of quantum mechanics is used to derive a new path
integral representation of the quantum density of state. A path integral Monte
Carlo approach is developed for the numerical investigation of the density of
states, internal energy and spin--resolved radial distribution functions for a
2D system of strongly correlated soft--sphere fermions. The peculiarities of
the density of states and internal energy distributions depending on the
hardness of the soft--sphere potential and particle density are investigated
and explained. In particular, at high enough densities the density of states
rapidly tends to a constant value, as for an ideal system of 2D fermions
Pressure of Coulomb systems with volume-dependent long-range potentials
In this work, we consider the pressure of Coulomb systems, in which particles
interact via a volume-dependent potential (in particular, the Ewald potential).
We confirm that the expression for virial pressure should be corrected in this
case. We show that the corrected virial pressure coincides with the formula
obtained by differentiation of free energy if the potential energy is a
homogeneous function of particle coordinates and a cell length. As a
consequence, we find out that the expression for pressure in the recent paper
by J. Liang \textit{et al.} [\href{https://doi.org/10.1063/5.0107140}{J. Chem.
Phys. \textbf{157}, 144102 (2022)}] is incorrect
Subsonic and supersonic gas flows to condensation surface
Intense heat-mass transfer in a gas flow to a condensation surface is studied
with the consistent atomistic and kinetic theory methods. The simple moment
method is utilized for solving the Boltzmann kinetic equation (BKE) for the
nonequilibrium gas flow and its condensation, while molecular dynamics (MD)
simulation of a similar flow is used for verification of BKE results. We
demonstrate that BKE can provide the steady flow profiles close to those
obtained from MD simulations in both subsonic and supersonic regimes of steady
gas flows. Surprisingly, the elementary theory of condensation is shown with
BKE results to have a good accuracy in a wide range of gas flow parameters.
MD confirms that a steady supersonic gas flow condensates on a surface at the
distinctive temperature after formation of a standing shock front in reference
to this surface, which can be interpreted as a permeable condensating piston.
The last produces the shock compression but completely absorbs incoming gas
flow in contrast to a common impermeable piston. The shock front divides the
vapor flow on the supersonic and subsonic zones, and condensation of compressed
gas happens in the subsonic regime. The complete and partial condensation
regimes are discussed. It is shown that above the certain surface temperatures
determined by the shock Hugoniot the runaway shock front stops an inflow gas
and condensation is ceased.Comment: 12 pages, 14 figure
Exchange--correlation bound states of the triplet soft--sphere fermions by the path integral Monte Carlo simulations
Path integral Monte Carlo simulations in the Wigner approach to quantum
mechanics has been applied to calculate momentum and spin--resolved radial
distribution functions of the strongly correlated soft--sphere quantum
fermions. The obtained spin--resolved radial distribution functions demonstrate
arising triplet clusters of fermions, that is the consequence of the
interference of exchange and interparticle interactions. The semiclassical
analysis in the framework of the Bohr--Sommerfeld quantization condition
applied to the potential of the mean force corresponding to the same--spin
radial distribution functions allows to detect exchange--correlation bound
states in triplet clusters and to estimate corresponding averaged energy
levels. The obtained momentum distribution functions demonstrate the narrow
sharp separated peaks corresponding to bound states and disturbing the
Maxwellian distribution.Comment: arXiv admin note: substantial text overlap with arXiv:2305.0760
The Effects of Preheating of a Fine Tungsten Wire and the Polarity of a High-Voltage Electrode on the Energy Characteristics of an Electrically Exploded Wire in Vacuum
Results obtained from experimental and numerical studies of tungsten wires
electrical explosion in vacuum are presented. The experiments were performed
both with and without preheating of the wires, using positive or negative
polarity of a high-voltage electrode. Preheating is shown to increase energy
deposition in the wire core due to a longer resistive heating stage. The effect
was observed both in single wire and wire array experiments. The evolution of
the phase state of the wire material during explosion was examined by means of
one-dimensional numerical simulation using a semiempirical wide-range equation
of state describing the properties of tungsten with allowance made for melting
and vaporization.Comment: 9 pages, 9 Postscript figure
Thermodynamic properties and electrical conductivity of strongly correlated plasma media
We study thermodynamic properties and the electrical conductivity of dense
hydrogen and deuterium using three methods: classical reactive Monte Carlo
(REMC), direct path integral Monte Carlo (PIMC) and a quantum dynamics method
in the Wigner representation of quantum mechanics. We report the calculation of
the deuterium compression quasi-isentrope in good agreement with experiments.
We also solve the Wigner-Liouville equation of dense degenerate hydrogen
calculating the initial equilibrium state by the PIMC method. The obtained
particle trajectories determine the momentum-momentum correlation functions and
the electrical conductivity and are compared with available theories and
simulations
Hole crystallization in semiconductors
When electrons in a solid are excited to a higher energy band they leave
behind a vacancy (hole) in the original band which behaves like a positively
charged particle. Here we predict that holes can spontaneously order into a
regular lattice in semiconductors with sufficiently flat valence bands. The
critical hole to electron effective mass ratio required for this phase
transition is found to be of the order of 80.Comment: accepted for publication in J. Phys. A: Math. Ge
Influence of equation of state on interpretation of electrical conductivity measurements in strongly coupled tungsten plasma
We study the influence of equation-of-state (EOS) model on the interpretation
of electrical conductivity measurements in strongly coupled plasma of tungsten
by Korobenko et al. (2002 Plasma Physics Reports 28(12) 1008--1016). Three
different semiempirical EOS models for tungsten are used. Discrepancies in
obtained thermodynamic parameters and specific resistivity values as compared
with calculation results of Korobenko et al. are analysed.Comment: 11 pages, 5 Postscript figures, accepted for publication in J. Phys.
A: Math. Ge
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