A quantum path integral Monte Carlo approach J. Phys. A 55, 035001 (2021) for strongly correlated degenerate fermions has been modified to solve the 'fermionic sign problem'. The exchange interaction ...of fermions was presented in the form of a positive semidefinite Gram determinant which significantly simplified the calculations. The verification of this approach has been carried out by comparison of the calculated equation of state with experimental data for quantum and degenerate unpolarised
. The obtained results agree with experimental data in a wide range of reduced inverse density
and temperature
. The range includes the gaseous and liquid states as well as the regions of the respective phase transition and the critical point. For the first time spin-resolved pair distribution functions have been calculated to analyse the spatial arrangement of helium atoms. The calculated internal energy has been presented for the gaseous region of quantum
. The simulations have been carried out for the Lennard-Jones (LJ) potential with parameters
Å and
K.
We report the physical reasons of a curious decrease in the crater depth observed for long delays in experiments with two successive femtosecond pulses. Detailed hydrodynamic modeling demonstrates ...that the ablation mechanism is dumped when the delay between the pulses exceeds the electron-ion relaxation time. In this case, the interaction of the second laser pulse with the expanding target material leads to the formation of the second shock wave suppressing the rarefaction wave created by the first pulse. The evidence of this effect follows from the pressure and density profiles obtained at different delays after the first laser pulse.
In this study, we investigate the dependence of potential energy of the one–component plasma on the number of particles with pure Coulomb, Ewald, and angular–averaged Ewald potentials. We show that ...in the weakly–coupled regime, the Coulomb potential provides a faster convergence of the energy to the thermodynamic limit. However, in the medium‐ and, especially, strong‐coupling regime, the Ewald potential shows significantly better convergence. Thus, the criticism of the Ewald potential in Fraser et al. Phys. Rev. B 53, 1814 (1996) within classical simulations turns out to be unjustified in this case: the accounting for long‐range interaction effects greatly improves the N$$ N $$‐convergence of one–component plasma thermodynamic functions.
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•We study thermodynamics of LiD at high pressures and temperatures.•Calculations with 1 valence electron for Li underestimate pressure on LiD Hugoniot.•We detect weaker repulsion of ...Li ions with a frozen inner shell.•We obtain new data on double shock compression of 7LiD up to 1.2TPa.•Overlapping of cores limits the application of pseudopotentials for unordered state.
We analyze the contribution of the inner-shell electrons of Li and overlapping of pseudopotential cores to thermodynamic properties of 7LiD under compression using density functional theory and quantum molecular dynamics. At zero temperature there is no noticeable influence of 1s electrons of Li on pressure up to fivefold compression. However, shock compression reveals significant difference in pressure in calculations with 1 or 3 valence electrons for Li at pressures higher than 200GPa. This fact can be explained by the weaker repulsion of Li ions with the frozen inner shell rather than by the excitation of the inner-shell electrons. We estimate conditions at which the one-electron pseudopotential is inapplicable in the unordered phase. Also we obtain new data on double shock compression of 7LiD up to 1.2TPa in good agreement with available experiments.
•The transport and optical properties of liquid aluminum were calculated.•The calculation is based on the QMD, DFT and the Kubo–Greenwood formula.•The dependence of the results on the main technical ...parameters is examined.•Two different expressions for the dynamic Onsager coefficients are discussed.•The calculations are performed for aluminum at near-normal densities and temperatures from normal up to 20,000K.
This work is devoted to the ab initio calculation of transport and optical properties of aluminum. The calculation is based on the quantum molecular dynamics simulation, density functional theory and the Kubo–Greenwood formula. Mainly the calculations are performed for liquid aluminum at near-normal densities for the temperatures from melting up to 20,000K. The results on dynamic electrical conductivity, static electrical conductivity and thermal conductivity are obtained and compared with available reference and experimental data and the calculations of other authors. The influence of the technical parameters on the results is investigated in detail. The error of static electrical conductivity calculation is estimated to be about 20%; more accurate results require bigger number of atoms.
The results of numerical and experimental investigations of the shock-wave induced spall fracture of bulk samples with thickness up to 10 mm made of 304L stainless steel irradiated by a nanosecond ...relativistic high-current electron beam with duration of
∼
45 ns, electron energy of 1.35 MeV, and peak power density of
34
GW/cm
2
are presented. By a mathematical model developed for numerical simulation of the shock-wave dynamics, it was found that a quasi-planar shock wave with duration of
∼
0.2
μ
s
, and initial amplitude of 17 GPa was formed in the irradiated samples. The effects of orientation of
δ
-ferrite interlayers in the austenitic matrix relative to the shock wave direction on the spall fracture were experimentally investigated. It was found that spallation was carried out by mixed ductile–brittle fracture. For the transversal orientation of
δ
-ferrite, the contribution of a brittle fracture mode in the spallation is higher than that for the longitudinal orientation. In both cases, the spalled layer thickness increased almost linearly with the increase of the target thickness, which was in good agreement with literature data. By the comparison of experimental data with simulation results, it was revealed that the spall strength can be estimated as 6.1 GPa at strain rate
0.48
μ
s
-
1
and 3.4 GPa at strain rate 0.18
μ
s
-
1
, for samples with the longitudinal and transversal orientation of
δ
-ferrites, respectively. The comparison of the obtained spall strength values with literature data is considered.
We establish a modification of the one-dimensional two-phase Stefan problem which is promising for the investigation of ultrafast processes in solids lasting less than the time of electron-phonon ...relaxation. Under such conditions the heat equations should be solved separately for ions and electrons at constant volume. We discuss the system of equations and boundary conditions for this special case and derive the computational scheme for the numerical solution. To demonstrate our new approach we calculate the electronic and ionic temperatures in an aluminum target subjected to a femtosecond laser pulse.
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