Quasi-isentropic compressibility of a strongly nonideal deuterium plasma at pressures of up to 5500 GPa: Nonideality and degeneracy effects

A new wave packet molecular dynamics–density functional theory (WPMD‐DFT) method is proposed for atomistic simulations of non‐ideal plasma and warm dense matter. The method is based on the WPMD approach, where the electronic exchange and correlation effects are treated using an additional energy term taken from DFT. This term is calculated by integration over the mesh values of the wave packet density. The local density approximation is implemented so far. WPMD‐DFT is meant as a replacement for the anti‐symmetrized WPMD (AWPMD) method which is more time consuming and lacks electron correlation. In this paper, we compare the results obtained by WPMD‐DFT, WPMD, AWPMD, classical molecular dynamics, and path integral Monte Carlo methods for the internal energy of the hydrogen plasma in the temperature range 10–50 kK and electron number density from 1020 to 1024 cm−3. We also demonstrate the ability to handle the simultaneous dynamics of electrons and ions by calculating the electron–ion temperature relaxation. The scalability of the WPMD‐DFT method with the number of electrons is shown for implementations in central processing unit and graphical processing unit.

Section: General Description Of the Algorithmmentioning

confidence: 99%

Section: General Description Of the Algorithmmentioning

confidence: 99%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

Wave packet molecular dynamics–density functional theory method for non‐ideal plasma and warm dense matter simulations

Lavrinenko

Морозов

Valuev

2019

“…Three diverse experimental approaches are applied: shock-wave reverberation hydrogen/deuterium experiments, [19][20][21][22][23][24][25] laser-driven shock waves in a hydrogen sample precompressed in a diamond anvil cell (DAC), [26][27][28][29][30][31][32] and a series of breakthrough dynamic compression experiments on liquid deuterium performed at the Sandia Z-machine. They searched in solid, but found in liquid hydrogen first.…”

Section: Experiments For Warm Dense Hydrogenmentioning

confidence: 99%

Plasma phase transition (by the fiftieth anniversary of the prediction)

Norman

Saitov

2019

At first, we present a brief review of the problem. Then, we consider plasma phase transition (PPT) as a mechanism of the first order fluid-fluid phase transition in warm dense hydrogen. The pros and cons are analysed. The properties of warm dense hydrogen are investigated by ab initio methods of molecular dynamics using the density functional theory. Strong ionization during the fluid-fluid phase transition in warm dense hydrogen makes this transition close to the prediction of the PPT. Finally, we present differences in the real phase transition from the prediction 1968-1969. Structures are observed with inter-proton separations that are equal to the distances between protons in the H + 2 and H + 3 ions. The transition is not only ionization, but also structural. An analysis of the phase transition counterpart in solid hydrogen under high pressure allows us to reveal partially the character of the new structure. The ionized phase includes complex cluster ions. Van der Waals loops are of abnormal inverted form. KEYWORDSdense hydrogen, density functional theory, pair correlation function, plasma phase transition INTRODUCTION: THREE PREDICTIONS OF 1968-1970The plasma phase transition (PPT) was predicted by Norman and Starostin [1] in 1968. The strong overlapping in the density of the equilibrium branch of one phase with a metastable branch of another phase was predicted in ref.[2]. The third prediction was a triple point on the melting curve. [3,4] Nature of the transitionThe hypothesis of PPT is advanced in ref.[1] by analogy with the van der Waals equation of state, where a first-order phase transition arises as a result of the competition between the long-range weak attraction and short-range strong repulsion between neutral particles, and temperature. In plasmas, due to the polarization of spatial charge distribution, the average Coulomb interaction energy of particles is negative and, therefore, has a general character of the long-range weak effective Coulomb attraction. This interaction is introduced into the expression for the free energy of plasma in the form of Debye-Hückel correction.where Γ = (4 /3) 1/3 e 2 n e 1/3 /kT is the Coulomb non-ideality parameter, T is the temperature, e is the elementary charge, k is the Boltzmann's constant, n e is the charge number density. In the region Γ > 1, the system becomes thermodynamically unstable. To stabilize the system of charged particles, a short-range effective quantum repulsion between free electrons and ions is taken into account in ref.[1], along with the Coulomb interaction. The localization of free charges at close distances leads to an increase

“…Both generation and diagnostics of matter need the best technique. Three diverse experimental approaches were applied: shock‐wave reverberation deuterium experiments, laser‐driven shock waves in a hydrogen sample pre‐compressed in a diamond anvil cell,– and a series of breakthrough dynamic compression experiments on liquid deuterium performed at the Sandia Z‐machine …”

Section: Introductionmentioning

confidence: 99%

Plasma phase transition in warm dense hydrogen

Norman

Saitov

2018

A new idea is developed that the fluid–fluid phase transition in warm dense hydrogen is related to the partial ionization of molecular hydrogen H2 with formation of molecular ions H2+ and H3+. Conventional ab initio quantum modelling is applied. The proton–proton pair correlation functions (PCFs) obtained are used for the non‐conventional diagnostics of the phase transition and elucidation of its nature for temperatures in the range 700–1500 K. Short‐ and long‐range changes of PCFs are studied. Ionization of H2 molecules and the appearance of molecular ions H2+ and H3+ are revealed. The validity of the soft sphere model is tested for the long‐range order.