Scientific Center of RAS in Chernogolovka

In the present Communication we discuss a field-induced and photoinduced self-doping chemistry resulting in the formation of the positively and negatively charged vacancies in the MAPbI3 perovskite films. These vacancies induce p-type and n-type doping of the perovskite absorber leading to the realization of the p-i-n device operation mechanism.

A rocket engine for Mars missions is proposed that could utilize CO2 accumulated from the Martian atmosphere as an oxidizer. For use as possible fuel, various metals, their hydrides, and mixtures with hydrogen compounds are considered. Thermodynamic calculations show that beryllium fuels ensure the most impulse but poor inflammability of Be and high toxicity of its compounds put obstacles to their applications. Analysis of the engine performance for other metals together with the parameters of ignition and combustion show that magnesium seems to be the most promising fuel. Ballistic estimates imply that a hopper with the chemical rocket engine on Mg + CO2 propellant could be readily developed. This vehicle would be able to carry out 2-3 ballistic flights on Mars before the final ascent to orbit.

Software documentation of Yade-DEM with some theoretical background. http://yade-dem.org

The advances and problems associated with the preparation, properties and structure of coordination polymers with chelated units are presented and assessed.

The effect of the phase composition on the α/β-Ti(Fe)→ω-Ti(Fe) transformation in the Ti-4 wt % Fe alloy under shear strain with high-pressure torsion (HPT) has been studied. For shear deformation by means of HPT, two initial states of the alloy were used, which significantly differed in the morphology of the phases and the concentration of iron atoms in the β phase. During HPT, a stationary state occurred in both sample series, which is characterized by the presence of a single ω phase containing 4 wt % Fe and by a grain size of about 200 nm. Thus, the HPT state is equifinal and independent of the initial phase composition of the samples. It was found that under the influence of HPT in Ti-4 wt % Fe alloys not only martensitic (shear) transformation into the ω phase occurs, but also a significant mass transfer of atoms of the alloying element. An analysis of the change in the torsion torque directly in the HPT process made it possible to estimate the rate of deformation-induced mass transfer. It is 18–19 orders of magnitude higher than the rate of conventional thermal diffusion at the processing temperature THPT = 30°C, while it is close to the diffusivity values at 700–800°C. This is because HPT increases the concentration of lattice defects, which in turn is equivalent to an increase in temperature. A similar combination of accelerated mass transfer during HPT and martensitic (shear) transformation was previously observed in copper-based shape memory alloys, but for the first time studied for the formation of ω-phase in titanium alloys.

The severe plastic deformation strongly changes the microstructure and properties of titanium-based alloys. The structure and microhardness of four binary and ternary titanium-based alloys (Ti–4 wt. % V, Ti–4 wt. % V–6 wt. % Al, Ti–4 wt. % V–3 wt. % Al, and Ti–5 wt. % V–6 wt. % Al) have been studied after preliminary annealing and following high pressure torsion (HPT). After HPT, the Ti–4 wt. % V alloy contains much less (ωTi) phase than Ti–4 wt. % Fe and Ti–4 wt. % Co alloys. The addition of aluminum to the binary Ti–V alloys completely suppresses the formation of the high-pressure (ωTi)-phase. HPT leads to the partial decomposition of the annealed (αTi) solid solution and “purification” of α-phase similar to that in the Ti–Fe alloys. After HPT of the studied ternary alloys, the (βTi)-phase completely disappears and nanoparticles of Ti2Fe form instead. This fact explains why the addition of aluminum leads to the increase of microhardness of alloys after annealing between 600 °C and 950 °C and after HPT-treatment. The increase of the temperature of the preliminary annealing also increases the hardness of all alloys after HPT-treatment.

Angular magnetoresistance oscillations have been studied systematically for β-(ET)2 IBr2 in the magnetic field rotating in a series of planes perpendicular to the conducting (a, b)-plane. The oscillations have been found in all studied planes. The shape of the Fermi surface transverse cross-section has been reconstructed using the obtained data. Angular dependence of the slow Shubnikov-de Haas oscillations frequency and some fine features of angular magnetoresistance oscillations permit to discuss also the structure of the Fermi surface longitudinal cross-section. The Fermi surface consists most likely of main cylinders with inclined warping planes and small pockets or necks between them.

Severe plastic deformation (SPD) can induce various phase transformations. After a certain strain, the dynamic equilibrium establishes between defects production by an external force and their relaxation (annihilation). The grain size, hardness, phase composition etc. in this steady-state does not depend on the initial state of a material and is, therefore, equifinal. In this review we discuss the competition between precipitation and dissolution of precipitates, amorphization and (nano)crystallization, SPD-induced accelerated mass-transfer, allotropic and martensitic transitions and formation of grain boundary phases.

In this review, the phenomenon of grain boundary (GB) wetting by melt is analyzed for multicomponent alloys without principal components (also called high-entropy alloys or HEAs) containing titanium. GB wetting can be complete or partial. In the former case, the liquid phase forms the continuous layers between solid grains and completely separates them. In the latter case of partial GB wetting, the melt forms the chain of droplets in GBs, with certain non-zero contact angles. The GB wetting phenomenon can be observed in HEAs produced by all solidification-based technologies. GB leads to the appearance of novel GB tie lines Twmin and Twmax in the multicomponent HEA phase diagrams. The so-called grain-boundary engineering of HEAs permits the use of GB wetting to improve the HEAs’ properties or, alternatively, its exclusion if the GB layers of a second phase are detrimental.

A novel composite adsorbent, consisting of three-dimensional honeycomb-like porous carbon and MnO₂ nanowires (HLPC/MnO₂), has been successfully synthesized and is an excellent adsorbent for removing uranium(<sc>vi</sc>) ions from aqueous solutions.

Optical memory devices based on photoswitchable OFETs comprising light sensitive layers of photochromic spiropyran salts revealed advanced electrical characteristics and superior stability.

Metallopolymers (MPs) or metal-containing polymers have shown great potential as self-healing and shape memory materials due to their unique characteristics, including universal architectures, composition, properties and surface chemistry. Over the past few decades, the exponential growth of many new classes of MPs that deal with these issues has been demonstrated. This review presents and assesses the latest achievements and problems associated with the use of MPs as self-healing and shape memory materials. Among the most widely used MPs with self-healing properties, metal complexes based on polymers containing phenol, carboxylic acid, pyridine, azole, histidine and urethane donor fragments are identified. Particular attention is paid to the principles of action of the shape memory MPs. Of considerable interest is the use of MPs as functional materials for sensors, soft electronic devices, transistors, conductors, nanogenerators, bone tissue engineering, etc. Finally, the problems and future prospects of MPs with self-healing and shape memory properties are outlined. This review also analyzes articles published over the past five years.

It was shown that ESR spectroscopy is a very useful technique for monitoring the photochemical and thermal degradation of conjugated polymers commonly used in organic solar cells. The relative stability of materials can be quantified by comparing the rates of trap accumulation (dC(R)/dt) estimated from their ESR profiles.

Structurally different complex bismuth iodides with 1D anionic frameworks were designed and explored as semiconductor materials for photovoltaic devices.

Optical memory elements based on photoswitchable organic field-effect transistors have been designed by using an interfacial layer of photochromic spirooxazine molecules sandwiched between semiconductor and dielectric layers. Optical and electrical programming of the designed devices leads to multiple discrete states demonstrating drastically different electrical characteristics (VTH, IDS) and advanced stability.

The molecular metals BET 2 [MCl 4 ] with M = Fe, Ga (see article title for BET) have been prepared and their structural, transport, and magnetic properties investigated. It is shwon that the conducting layers of the organic donor BET are interleaved by the inorganic ions, which are fairly well isolated from each other in the crystal. However, in the case of the Fe, the ions are found not to be magnetically isolated but coupled by exchange interactions. A mechanism is suggested to account for the observed Fe–Fe interaction in this magnetic molecular metal.

ConspectusChemistry is controlled by Coulomb energy; magnetic energy is lower by many orders of magnitude and may be confidently ignored in the energy balance of chemical reactions. The situation becomes less clear, however, when reaction rates are considered. In this case, magnetic perturbations of nearly degenerate energy surface crossings may produce observable, and sometimes even dramatic, effects on reactions rates, product yields, and spectroscopic transitions. A case in point that has been studied for nearly five decades is electron spin-selective chemistry via the intermediacy of radical pairs. Magnetic fields, external (permanent or oscillating) and the internal magnetic fields of magnetic nuclei, have been shown to overcome electron spin selection rules for pairs of reactive paramagnetic intermediates, catalyzing or inhibiting chemical reaction pathways. The accelerating effects of magnetic stimulation may therefore be considered to be magnetic catalysis. This type of catalysis is most commonly observed for reactions of a relatively long-lived radical pair containing two weakly interacting electron spins formed by dissociation of molecules or by electron transfer. The pair may exist in singlet (total electron spin is zero) or triplet (total spin is unity) spin states. In virtually all cases, only the singlet state yields stable reaction products. Magnetic interactions with nuclear spins or applied fields may therefore affect the reactivity of radical pairs by changing the angular momentum of the pairs.Magnetic catalysis, first detected via its effect on spin state populations in nuclear and electron spin resonance, has been shown to function in a great variety of well-characterized reactions of organic free radicals. Considerably less well studied are examples suggesting that the basic mechanism may also explain magnetic effects that stimulate ATP synthesis, eliminating ATP deficiency in cardiac diseases, control cell proliferation, killing cancer cells, and control transcranial magnetic stimulation against cognitive deceases. Magnetic control has also been observed for some processes of importance in materials science and earth and environmental science and may play a role in animal navigation.In this Account, the radical pair mechanism is applied as a consistent explanation for several intriguing new magnetic phenomena. Specific examples include acceleration of solid state reactions of silicon by the magnetic isotope 29Si, enrichment of 17O during thermal decomposition of metal carbonates and magnetic effects on crystal plasticity. In each of these cases, the results are consistent with an initial one-electron transfer to generate a radical pair. Similar processes can account for mass-independent fractionation of isotopes of mercury, sulfur, germanium, tin, iron, and uranium in both naturally occurring samples and laboratory experiments. In the area of biochemistry, catalysis by magnetic isotopes has now been reported in several reactions of DNA and high energy phosphate. Possible medical applications of these observations are pointed out.

Photochemical degradation of fullerene derivatives producing persistent radical species represents one of the key failure mechanisms of organic solar cells.

Population annealing is a promising recent approach for Monte Carlo simulations in statistical physics, in particular for the simulation of systems with complex free-energy landscapes. It is a hybrid method, combining importance sampling through Markov chains with elements of sequential Monte Carlo in the form of population control. While it appears to provide algorithmic capabilities for the simulation of such systems that are roughly comparable to those of more established approaches such as parallel tempering, it is intrinsically much more suitable for massively parallel computing. Here, we tap into this structural advantage and present a highly optimized implementation of the population annealing algorithm on GPUs that promises speed-ups of several orders of magnitude as compared to a serial implementation on CPUs. While the sample code is for simulations of the 2D ferromagnetic Ising model, it should be easily adapted for simulations of other spin models, including disordered systems. Our code includes implementations of some advanced algorithmic features that have only recently been suggested, namely the automatic adaptation of temperature steps and a multi-histogram analysis of the data at different temperatures. Program Title: PAIsing Program Files doi: http://dx.doi.org/10.17632/sgzt4b7b3m.1 Licensing provisions: Creative Commons Attribution license (CC BY 4.0) Programming language: C, CUDA External routines/libraries: NVIDIA CUDA Toolkit 6.5 or newer Nature of problem: The program calculates the internal energy, specific heat, several magnetization moments, entropy and free energy of the 2D Ising model on square lattices of edge length L with periodic boundary conditions as a function of inverse temperature β. Solution method: The code uses population annealing, a hybrid method combining Markov chain updates with population control. The code is implemented for NVIDIA GPUs using the CUDA language and employs advanced techniques such as multi-spin coding, adaptive temperature steps and multi-histogram reweighting. Additional comments: Code repository at https://github.com/LevBarash/PAising. The system size and size of the population of replicas are limited depending on the memory of the GPU device used. For the default parameter values used in the sample programs, L=64, θ=100, β0=0, βf=1, Δβ=0.005, R=20000, a typical run time on an NVIDIA Tesla K80 GPU is 151 seconds for the single spin coded (SSC) and 17 seconds for the multi-spin coded (MSC) program (see Section 2 for a description of these parameters).

and demonstrates excellent (>2.5 M) solubility in MeCN. A non-aqueous organic redox flow battery assembled using the novel phenazine derivative as an anolyte and a substituted triarylamine derivative as a catholyte exhibited high specific capacity (∼93% from the theoretical value), >95% Coulombic efficiency, 65% utilization of active materials and good charge-discharge cycling stability.