Computational design of new superconducting materials and their targeted experimental synthesis

In the last six years (2015-2021), many superconducting hydrides with critical temperatures $\textit{T}$$_C$ of up to 253 K, a record for today, have been discovered. Now, a special field of hydride superconductivity at ultrahigh pressures has developed. For the most part, the properties of superhydrides are well described by the Migdal-Eliashberg theory of strong electron-phonon interaction, especially when anharmonicity of phonons is taken into account. The isotope effect, the effect of the magnetic field (up to 60-70 T) on the critical temperature and critical current in the hydride samples, the dependence of $\textit{T}$$_C$ on the pressure and degree of doping - all data indicate that polyhydrides are conventional superconductors, the theory of which was created by Bardeen, Cooper, and Schrieffer in 1957. This work presents a retrospective analysis of data for 2015-2021 and describes the main directions for future research in the field of hydride superconductivity. The thesis consists of six chapters devoted to the study of the structure and superconductivity of binary and ternary superhydrides of thorium (ThH$_9$ and ThH$_{10}$), yttrium (YH$_6$ and YH$_9$), europium and other lanthanides (Ce, Pr, Nd), and lanthanum-yttrium (La-Y). This work describes the physical properties of cubic decahydrides, hexahydrides, and hexagonal metal nonahydrides, demonstrates high efficiency of evolutionary algorithms and density functional methods in predicting the formation of polyhydrides under high-pressure and high-temperature conditions. We proposed a theoretical-experimental algorithm for analyzing the superconducting properties of hydrides, which makes it possible to systematize the accumulated experimental data. In general, this research is a vivid example of the effectiveness and synergy of modern methods for studying the condensed state of matter under high pressures

LCLD Laser Processing Technology for Microelectronics Printed- circuit Boards of New Generation

AbstractThis paper has dealt with the formation mechanism of nanosized metal coatings on dielectrics; the coatings were produced using laser-induced deposition from liquid phase. A diode-pumped solid-state (DPSS) laser (532nm) was used in the deposition experiments. The laser power varied from 500 to 1500 mW with the single scanning rate up to 50μm/s. The deposited copper structures were studied by the scanning electron microscopy (SEM) and energy-dispersive X-ray microanalysis (EDX) methods. The main attention in the paper was given to studying the effect of laser light pressure on the solid nanoparticles. There was constructed the qualitative model of nanoparticles formation during salt film decomposition at the hetero-phase “gas/liquid” border. The radiation energies thermalized by nanoparticles were calculated, and assessment of their temperature was found

The Technology of Laser-Induced Deposition of Nanostructured Metallic Conductors on the Dielectric Substrate

This article describes a new method for planar copper-oxide coatings with controlled topology and the nanostructured surface. The structure obtained by laser-induced deposition of copper-containing aqueous solutions of a semiconductor laser (532 nm) radiation in a continuous mode. The method Energy Dispersive X-Ray spectroscopy to study the composition of the obtained nanoparticles. Particle sizes were determined by scanning electron microscopy. When you are citing the document, use the following link http://essuir.sumdu.edu.ua/handle/123456789/3547

Ternary superconducting hydrides in the La-Mg-H system

Ternary or more complex hydrogen-rich hydrides are the main hope of reaching room-temperature superconductivity at high pressures. Their chemical space is vast and its exploration is challenging. Here we report the investigation of the La-Mg-H ternary system using the evolutionary algorithm USPEX at pressures on the range 150-300 GPa. Several ternary superconducting hydrides were found, including thermodynamically stable $P6/mmm$-LaMg$_{3}$H$_{28}$ with $T_{\mathrm{C}}=164$~K at 200~GPa, $P/2m$-LaMgH$_8$, $C2/m$-La$_2$MgH$_{12}$ and $P2/m$-La$_3$MgH$_{16}$. In addition, novel binary hydrides were predicted to be stable at various pressures, such as $Cm$-Mg$_6$H$_{11}$, $P1$-MgH$_{26}$, $Fmm2$-MgH$_{30}$, $P1$-MgH$_{38}$ and $R\overline{3}m$-LaH$_{13}$. We also report several novel low-enthalpy metastable phases, both ternary and binary ones. Finally, we demonstrate important methods of exploring very large chemical spaces and show how they can improve crystal structure prediction

Stabilization of high-temperature superconducting A15 phase La4_4H23_{23} below 100 GPa

High pressure plays a crucial role in the field of superconductivity. Compressed hydride superconductors are leaders in the race for a material that can conduct electricity without resistance at high or even room temperature. Different synthetic paths under pressure will drive the formation of different polyhydrides. In the present work, through precise control of the synthesis pathway, we have discovered new lanthanum superhydride, cubic A15-type La$_4$H$_{23}$, with lower stabilization pressure compared to the reported $\textit{fcc}$ LaH$_{10}$. Superconducting La$_4$H$_{23}$ was obtained by laser heating of LaH$_3$ with ammonia borane at about 120 GPa. Transport measurements reveal the maximum critical temperature $\textit{T}$$_{C}$(onset) = 105 K at 118 GPa, as evidenced by the sharp drop of electrical resistance and the displacement of superconducting transitions in applied magnetic fields. Extrapolated upper critical field $\textit{B}$$_{C2}$(0) of La$_4$H$_{23}$ is about 33 T at 114 GPa in agreement with theoretical estimates. Discovered lanthanum hydride is a new member of the A15 family of superconductors with $\textit{T}$$_C$ exceeding the boiling point of liquid nitrogen