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## Molecules ionization at phase transition in warm dense hydrogen

Journal of Physics: Conference Series. 2018. Vol. 946. No. 012121.

Norman G., Saitov I.

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 modeling is applied. Proton pair correlation functions (PCF) obtained are used for the nonconventional diagnostics of the phase transition and elucidation of its nature for temperatures 700-1500 K. Short- and longrange changes of PCF’s are studied. H2 molecules ionization and molecular ions H2+ and H3+ appearance is revealed. The validity of the soft sphere model is tested for the long-range order.

Norman G., Saitov I., Contributions to Plasma Physics 2018 Vol. 58 No. 2-3 P. 122-127

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 H+2 and H+3 . 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 ...

Added: June 8, 2018

Norman G., Saitov I., Доклады Российской академии наук. Физика, технические науки (ранее - Доклады Академии Наук. Физика) 2017 Т. 474 № 6 С. 687-691

The density functional theory is used to calculate the equation of state and the proton-proton pair correlation functions in the range of hydrogen temperatures and densities where the fluid-fluid-phase transition is expected. The metastable states are considered. The critical temperature has been estimated to be ~4000 K. We propose a two-step mechanism: the partial ionization ...

Added: December 2, 2017

Norman G., Saitov I., Contributions to Plasma Physics 2019 Vol. 59 No. 6 P. e201800182

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 ...

Added: October 30, 2019

Norman G., Saitov I., Доклады Российской академии наук. Физика, технические науки (ранее - Доклады Академии Наук. Физика) 2017 Т. 474 № 5 С. 553-557

The problem of the fluid–fluid phase transition in warm dense hydrogen/deuterium has been studied experimentally and theoretically in the best laboratories in the last decade. However, the nature of the phase transition remains unclarified. In this paper we put forward the new idea that H2 molecules are ionized at the phase transition to produce molecular ...

Added: December 2, 2017

Norman G., Saitov I., Sartan R., Interfacial Phenomena and Heat Transfer 2017 Vol. 5 No. 3 P. 165-171

Warm dense hydrogen is investigated by ab initio molecular dynamics simulations in the region of fluid–fluid phase
transition. The method of getting adjacent metastable states is developed. The metastable states are successfully obtained in the region of densities from 0.920 to 0.970 g/cm3 and pressures from 1850 kbar to 2150 kbar along an example of 1000K ...

Added: June 15, 2018

Norman G., Saitov I., Stegailov V., Contributions to Plasma Physics 2015 Vol. 55 No. 2-3 P. 215-221

Ab initio quantum modeling is applied to check the ideas that motivated studies of both plasma phase transition (PPT) and Brazhkin semiconductor-to-metal phase transition, and to analyze both similarity and difference between them as well as with the Wigner metallization. Electron density of states and the characteristic gap in it are investigated to verify the ...

Added: March 15, 2017

Stegailov V., Zhilyaev P. A., Contributions to Plasma Physics 2015 Vol. 55 No. 2-3 P. 164-171

Non-equilibrium two-temperature warm dense metals consist of the ion subsystem that is subjected to structural transitions and involved in the mass transfer, and the electron subsystem that in various pulsed experiments absorbs energy and then evolves together with ions to equilibrium. Definition of pressure in such non-equilibrium systems causes certain controversy. In this work we ...

Added: March 15, 2017

Zhang L., Vasenko A.S., Zhao J. et al., The Journal of Physical Chemistry Letters 2019 Vol. 10 No. 5 P. 1083-1091

An attractive two-dimensional semiconductor with tunable direct bandgap and high carrier mobility, black phosphorus (BP) is used in batteries, solar cells, photocatalysis, plasmonics and optoelectronics. BP is sensitive to ambient conditions, with oxygen playing a critical role in structure degradation. Our simulations show that BP oxidation slows down charge recombination. This is unexpected, since typically ...

Added: February 19, 2019

Li W., Vasenko A.S., Tang J. et al., The Journal of Physical Chemistry Letters 2019 Vol. 10 No. 20 P. 6219-6226

Lead halide perovskites constitute a very promising class of materials for a broad range of solar and opto-electronic applications. Perovskites exhibit many unusual properties, and recent experiments demonstrate an unusual temperature dependence of charge carrier lifetimes. Focusing on the all-inorganic CsPbBr3, and using a combination of ab initio nonadiabatic molecular dynamics and time-domain density functional ...

Added: September 30, 2019

Zubizarreta X., Chulkov E. V., Chernov I. P. et al., Physical Review B: Condensed Matter and Materials Physics 2017 Vol. 95 No. 235405 P. 235405-1-235405-15

A theoretical study of collective electronic excitations in free-standing Pb(111) thin films consisting of 1–5 monolayers (MLs) and a 21-ML film is presented. The calculations are carried out applying the linear response theory, with full inclusion of the electron band structure by means of a first-principles pseudopotential approach in a supercell scheme. In the case ...

Added: June 6, 2017

Norman G., Saitov I., Stegailov V. et al., Physical Review E - Statistical, Nonlinear, and Soft Matter Physics 2015 Vol. 91 No. 023105 P. 1-10

Reflectivity of shocked compressed xenon plasma is calculated within the framework of the density functional theory approach. Dependencies on the frequency of incident radiation and on the plasma density are analyzed. The Fresnel formula for the reflectivity is used. The longitudinal expression in the long-wavelength limit is applied for the calculation of the imaginary part ...

Added: March 15, 2017

Korsun O. M., Kalugin O. N., Vasenko A. S. et al., Journal of Physical Chemistry C 2016 Vol. 120 No. 46 P. 26514-26521

The influence of bare and solvated cations imbedded inside single-walled carbon nanotubes (SWCNTs) on the SWCNT electronic properties is studied by ab initio electronic structure calculations. The roles of ion charge and ion solvation are investigated by comparing Li+ vs Mg2+ and Li+ vs its solvatocomplex with two ethylene carbonate (EC) molecules, [Li(EC)2]+. Two achiral ...

Added: November 22, 2016

Saitov I., Журнал экспериментальной и теоретической физики 2020 Т. 157 № 3 С. 504-512

Density-functional theory (DFT) is applied to the calculation of the equation of state, the pair correlation
function (PCF), and the static electrical conductivity of solid hydrogen near the transition point to
the conducting state. It is found that the pressure versus density exhibits hysteresis at temperature of 100 K
under compression followed by expansion. The overlapping of the ...

Added: October 29, 2022

He J., Vasenko A.S., Long R. et al., The Journal of Physical Chemistry Letters 2018 Vol. 9 No. 8 P. 1872-1879

We demonstrate that halide content strongly affects nonradiative electron–hole recombination in all-inorganic perovskite quantum dots (QDs). Using time domain density functional theory and nonadiabatic molecular dynamics, we show that replacing half of the bromines with iodines in a CsPbBr3 QD extends the charge carrier lifetime by a factor of 5, while complete replacement extends the ...

Added: March 31, 2018

Norman G., Saitov I., Успехи физических наук 2021 Т. 191 № 11 С. 1153-1186

Recently developed experimental methods for the generation and diagnostics of nonideal plasma and warm dense
matter are reviewed. Modern theoretical methods applied to solve the problem of fluid±fluid phase transitions, including the plasma phase transition, are considered. Quantum simulation methods and the results obtained in the chemical model of plasma are analyzed. Particular attention is paid ...

Added: October 29, 2022

Nuraliev M., Parashchuk O., Tukachev N. et al., Journal of Chemical Physics 2020 Vol. 153 Article 174303

Electron–phonon interaction strongly affects and often limits charge transport in organic semiconductors (OSs). However, approaches to its experimental probing are still in their infancy. In this study, we probe the local electron–phonon interaction (quantified by the charge-transfer reorganization energy) in small-molecule OSs by means of Raman spectroscopy. Applying density functional theory calculations to four series ...

Added: October 18, 2021

T.V. Pavlova, G.M. Zhidomirov, K.N. Eltsov, The Journal of Physical Chemistry C (США) 2018 Vol. 122 No. 3 P. 1741-1745

This paper presents a density functional theory study for phosphine adsorption on a Si(001)-2 × 1 surface covered by a chlorine monolayer, including adsorption on local defects, i.e., mono- and bivacancies in the adsorbate layer (Cl, Cl2), and combined vacancies with removed silicon atoms (SiCl, SiCl2). Activation barriers were found for the adsorbing PH3 to dissociate ...

Added: January 10, 2019

Norman G., Saitov I., Doklady Physics 2019 Vol. 64 No. 4 P. 145-149

—The structural transformation of solid hydrogen under compression along the isotherm of 100 K in
the region of transition into the conductive state was studied within the density functional theory. The pressure, the pair correlation function of protons, the density of electron states, and the electrical conductivity were calculated within a range of hydrogen densities from ...

Added: October 30, 2019

Stegailov V., Zhilyaev P., Molecular Physics 2016 Vol. 114 No. 3-4 P. 509-518

Warm dense matter is a peculiar state with solid densities and temperatures 1 − 100 eV. Its ab initio description waits united efforts of quantum chemistry, condensed matter and plasma physics. We use the finite temperature Kohn–Sham density functional theory (a ‘workhorse’ in this field) to study the pressure build-up with increase of electronic temperature in ...

Added: July 5, 2016

Medvedev M., Bushmarinov I., Sun J. et al., Science 2017 Vol. 355 No. 6320 P. 49-52

The theorems at the core of density functional theory (DFT) state that the energy of a many-electron system in its ground state is fully defined by its electron density distribution. This connection is made via the exact functional for the energy, which minimizes at the exact density. For years, DFT development focused on energies, implicitly ...

Added: October 12, 2019

Medvedev M., Marjewski A., Gerasimov I. et al., Mendeleev Communications 2018 Vol. 28 No. 3 P. 225-235

The task of choosing a reliable density functional (DFT) approximation remains one of the most puzzling ones in quantum chemical modeling and materials simulations. Since DFT functionals are in general not systematically improvable, benchmarking them on specifically designed test sets is the usual way for identifying a method best suited for a particular purpose. To ...

Added: October 12, 2019

Saitov I., Molecular Physics 2016 Vol. 114 No. 3-4 P. 446-452

Density functional theory (DFT) is applied for the calculation of the dielectric function (DF), reflectivity,
conductivity, plasma frequency and effective free electron density of warm dense matter
(WDM). Shock-compressed xenon plasma and warm dense hydrogen are considered. The longitudinal
expression in the long wavelength limit is applied for the calculation of the imaginary part of
the DF. The real ...

Added: March 30, 2017

Nagaev K., Маношин А. А., Physical Review B: Condensed Matter and Materials Physics 2020 Vol. 102 Article 155411

We calculate the electrical and thermal conductivity of a two-dimensional electron gas with strong spin-orbit
coupling in which the scattering is dominated by electron-electron collisions. Despite the apparent absence of
Galilean invariance in the system, the two-particle scattering does not affect the electrical conductivity above
the band-crossing point where both helicity bands are filled. Below the band-crossing point ...

Added: October 14, 2021

Alfimov M., Litvinov A., Journal of High Energy Physics 2022 No. 01 Article 43

We study regularization scheme dependence of beta-function for sigma models with two-dimensional target space. Working within four-loop approximation, we conjecture the scheme in which the beta-function retains only two tensor structures up to certain terms containing zeta_3. Using this scheme, we provide explicit solutions to RG flow equation corresponding to Yang-Baxter- and lambda-deformed SU(2)/U(1) sigma ...

Added: February 1, 2022