arXiv subjects

Nadezhda A. Andreeva

Publications and source records attributed to Nadezhda A. Andreeva.

13 recordsLinked to original sources

arXiv2026

Ozonation of Dielectric Fosters Self-Healing Efficiency in Metalized-Film Capacitors: Quantum-Chemical Simulation

Metalized-film capacitors (MFCs) employ polymer organic dielectrics like polypropylene (PP) and polyimide (PI), in which self-healing is seen as a key advantage. However, the performance of self-healing depends on specific chemical mechanisms involved. The formation of semiconductive carbonaceous soot represents a critical failure risk. This study investigates how oxygen atom impregnation through ozonation of the dielectric material tunes the composition and electrical conductivity of breakdown products in the PP and PI systems with aluminum-zinc electrodes. We revealed, at the atomistic level, that oxygen atoms tend to remove a fraction of carbon atoms from the semiconductive soot by oxidizing carbon into carbon monoxide in both polymers. In PP, oxygen fraction linearly increases gas mass fraction, thereby reducing soot fraction. In PI, the gas/soot ratio effect of oxygen content is less drastic, still clearly positive. The PP soot conductivity decreases uniformly as larger fractions of oxygen atoms are added. In turn, the PI conductivity drops to ~1500 S/m quickly. The PI soot exhibits narrower band gaps compared to that of PP. The oxygen fraction non-monotonically tailors band gaps, which generally increase. To summarize, ozonation enhances MFC reliability by increasing gas species fraction and reducing soot conductivity. We hereby provide numerical molecular-level insights to rationalize self-healing performance enhancement through polymer ozonation.

cond-mat.mtrl-sci↗

arXiv2024

Chemical Compositions of Soot Samples in Gold Electrode Capacitors: Molecular Simulations

Electrical breakdown in a dielectric capacitor occurs when the electric field strength across the dielectric material exceeds its breakdown strength. A conductive channel through the dielectric emerges, resulting in a sudden surge of current. Self-healing represents a phenomenon of restoration of a capacitor's performance. The efficiency of self-healing depends on the products of high-temperature decomposition of the electrode and dielectric. We report atomistic simulations of the soot's chemical composition in the case of gold electrodes and four popular dielectric polymers: polypropylene (PP), polyethylene terephthalate (PET), polycarbonate (PC), and polyimide (PI). We unravel that gold atoms form clusters within the carbon-rich soot, limiting their interactions with non-metal elements. The oxygen atoms of PET, PC, and PI act as stabilizers of gold thanks to electrostatic attraction. Compared to zinc, gold equalizes the soot conductivity in all samples but does not impact polymer gasification. The suitability of dielectrics for self-healing must be rated based on the volatile by-products: PP > PC > PET > PI. Mind that PP issues three times more gases than PI. Therefore, the size of semiconducting soot is substantially smaller in the case of PP than in the case of PI. The obtained numerical results provide unprecedented physical insights into the phenomenon of self-healing and clearly drive the efforts to extend the lifespans of the metalized film capacitors.

cond-mat.mtrl-sci↗

arXiv2024

Self-Healing in Dielectric Capacitors: a Universal Method to Computationally Rate Newly Introduced Energy Storage Designs

Metal-film dielectric capacitors provide lump portions of energy on demand. While the capacities of various capacitor designs are comparable in magnitude, their stabilities make a difference. Dielectric breakdowns - micro-discharges - routinely occur in capacitors due to the inevitable presence of localized structure defects. The application of polymeric dielectric materials featuring flexible structures helps obtain more uniform insulating layers. At the modern technological level, it is impossible to completely avoid micro-discharges upon device exploitation. Every micro-discharge results in the formation of a soot channel, which is empirically known to exhibit semiconductor behavior. Because of its capability to conduct electricity, the emerged soot channels harm the subsequent capacitor performance and decrease the amount of stored energy. The accumulation of the soot throughout a dielectric capacitor ultimately results in irreversible overall failure. In the context of the dielectric breakdown, self-healing designates a range of chemical processes, which spontaneously rearrange the atoms in the soot channels to partially return their insulative function. We developed a universal method capable of rating new capacitor designs including electrode and polymer material and their proportions. We found the best-performing designs produce abundant volatile by-products after micro-discharge, whereas the soot samples exhibit lower electronic conductivities. We proved the capability of the theoretical method to rate the empirical performance of the known capacitors. The method relies on various electronic-structure simulations and potential landscape explorations. The reported advance opens an impressive avenue to computationally probe thousands of hypothetical capacitor designs.

physics.app-ph↗

arXiv2024

Potential Energy Landscape as a Framework for Developing Innovative Materials

In the contemporary era of rapid advancements in materials science, the development of new compounds and materials is proceeding at an accelerated pace. The concept of the potential energy landscape (PEL) plays a pivotal role in supporting the meticulous engineering of novel structures. This review article examines the historical evolution of the PEL concept and its diverse applications in materials design. A comprehensive overview of the major methods employed to sample the PEL is presented, accompanied by a critical discussion highlighting relevant modern endeavors. Specific applications of the PEL in rationalizing the design of molecules and materials for energy storage, electrolytic solutions, and greenhouse gas capture are exemplified. This review serves as an up-to-date guide for exploring and analyzing the PEL, facilitating a deeper understanding of its significance in materials science.

cond-mat.mtrl-sci↗

arXiv2023

Revolutionary valorization of carbon dioxide into dimethyl carbonate is catalyzed by sodium chloride: cheap, clean, one-pot, and water-free synthesis

The robust valorization of carbon dioxide (CO2) stays at the center of sustainable development. Since CO2 represents a low-energy compound, its transformation into commercially coveted products is cumbersome. In the present work, we report a revolutionary method to obtain dimethyl carbonate (DMC) out of methanol (CH3OH) and CO2 catalyzed by sodium chloride (NaCl) and similar inorganic salts. The computational exploration revealed a mechanism of favorable catalysis, which was subsequently confirmed experimentally. Unlike all competitive syntheses of DMC, the new one does not produce water and, therefore, the hydrolysis of a carbonate does not occur. No dehydrating agents are necessary. The employed catalyst is cheap and permanently exists in the same phase with the reactants and products. The action of NaCl was compared to those of other alkali metal salts, LiI, LiCl, and KI, and competitive performances were recorded. The experimentally obtained result outperforms most competing technologies according to the DMC yield, 19% with molecular sieves and 17% without molecular sieves. All existing competitors are excelled by the simplicity and cleanness of the synthesis. The reported advance substantially simplifies the synthesis of linear organic carbonates and robustly valorizes CO2. Keywords: Dimethyl carbonate; carbon dioxide utilization; sodium chloride; methanol.

cond-mat.mtrl-sci↗

arXiv2022

Cathodic Carbon Chemically Adsorbs Carbon Dioxide: Why Is it True?

Large-scale applications are waiting for an optimal CO2 scavenger to reinforce CCS and CCU technologies. We herein introduce and succinctly validate a new philosophy of capturing gaseous CO2 by negatively-charged carbonaceous structures. The chemical absorption of CO2 turns out possible thanks to the emergence of significant nucleophilic interaction carbon centers upon applying voltage. The carbonaceous cathode, therefore, may serve as a prototype of a new CO2 sorbent. As a model to simulate chemisorption, we used a small-sized graphene quantum dot (GQD). According to the recorded reaction profiles, the negatively charged GQD containing 16 carbon atoms readily reacts with the CO2 molecule and produces carboxylated GQD. In turn, the activation energy (60 kJ/mol) and energy effect (-55 kJ/mol) for the reaction in water appeared surprisingly competitive in the context of the literature. We hypothesize that the carbonaceous cathode deserves in-depth experimental research as a possible CO2 chemical sorbent. Despite we used GQD for simulations, the encouraging results can be extrapolated to other nanoscale carbons and, more importantly, to the activated carbon species widely employed in modern electrochemical devices.

cond-mat.mtrl-sci↗

arXiv2021

Mixtures of Diethyl Sulfoxide and Methanol: Structure and Thermodynamics

Mixtures of sulfoxides with molecular solvents possess interesting physical-chemical properties and may have applications in chemical synthesis. Hereby we confirm and rationalize the previously reported excellent miscibility of diethyl sulfoxide (DESO) with methanol (MeOH). By performing a comprehensive potential energy surface investigation we identified a global minimum for each system and a significant number of local minima described at the hybrid density functional level of theory. A strong 0.18-nm-long hydrogen bond forming between the oxygen atom of DESO and the polarized hydrogen atom of MeOH was evidenced both via the structural and spectral analyses. Our results robustly explain negative deviations in the DESO-MeOH mixtures from ideal behavior and interpret the experimental observations with microscopic precision.

cond-mat.mtrl-sci↗

arXiv2021

Ammonium-, Phosphonium- and Sulfonium-Based 2-Cyanopyrrolidines for Carbon Dioxide Fixation

The development of carbon dioxide (CO2) scavengers is an acute problem nowadays because of the global warming problem. Many groups around the globe intensively develop new greenhouse gas scavengers. Room-temperature ionic liquids (RTILs) are seen as a proper starting point to synthesize more environmentally friendly and high-performance sorbents. Aprotic heterocyclic anions (AHA) represent excellent agents for carbon capture and storage technologies. In the present work, we investigate RTILs in which both the weakly coordinating cation and AHA bind CO2. The ammonium-, phosphonium- and sulfonium-based 2-cyanopyrrolidines were investigated using the state-of-the-art method to describe the thermochemistry of the CO2 fixation reactions. The infrared spectra, electronic and structural properties were simulated at the hybrid density functional level of theory to characterize the reactants and products of the chemisorption reactions. We conclude that the proposed CO2 capturing mechanism is thermodynamically allowed and discuss the difference between different families of RTILs. Quite unusually, the intramolecular electrostatic attraction plays an essential role in stabilizing the zwitterionic products of the CO2 chemisorption. The difference of chemisorption performance between the families of RTILs is linked to sterical hindrances and nucleophilicities of the α- and \b{eta}-carbon atoms of the aprotic cations. Our results are supported by the previous experimental CO2 sorption measurements and systematically extend their scope.

physics.chem-ph↗

arXiv2017

A Weakly Coordinating Anion Substantially Enhances Carbon Dioxide Fixation by Calcium and Barium Salts

Carbon dioxide fixation and storage constitute a drastically important problem for the humanity nowadays. We hereby publish a new solution based on the alkaline earth salts with a weakly coordinating anion, tetrakis(pentafluorophenyl)borate. The proposed solution was validated using a robust combination of global minimum search and molecular dynamics simulations utilizing a well-tested, reliable semiempirical Hamiltonian to monitor chemical reactions. Calcium tetrakis(pentafluorophenyl)borate captures 5.5 CO2 molecules per mole, whereas barium tetrakis(pentafluorophenyl)borate captures 3.6 CO2 molecules per mole. These capacities are much higher, as compared to the established carbonate technology, which fixes only one CO2 molecule per one metal atom. The conducted simulations reveal that electrostatic binding of CO2 to alkaline earth cations is more technologically interesting than formation of carbonate salts. Our simulation results can be directly validated by sorption measurements.

cond-mat.mtrl-sci↗

arXiv2017

Electronic and Thermodynamic Properties of the Amino- and Carboxamido-Functionalized C-60-Based Fullerenes: Towards Non-Volatile Carbon Dioxide Scavengers

Development of new greenhouse gas scavengers is actively pursued nowadays. Volatility caused solvent consumption and significant regeneration costs associated with the aqueous amine solutions motivate search for more technologically and economically advanced solutions. We hereby used hybrid density functional theory to characterize thermodynamics, structure, electronic and solvation properties of amino and carboxamido functionalized C60 fullerene. C60 is non-volatile and supports a large density of amino groups on its surface. Attachment of polar groups to fullerene C60 adjusts its dipole moment and band gap quite substantially, ultimately resulting in systematically better hydration thermodynamics. Reaction of polyaminofullerenes with CO2 is favored enthalpically, but prohibited entropically at standard conditions. Free energy of the CO2 capture by polyaminofullerenes is non-sensitive to the number of amino groups per fullerene. This result fosters consideration of polyaminofullerenes for CO2 fixation.

cond-mat.mtrl-sci↗

arXiv2017

Structure, Thermodynamic and Electronic Properties of Carbon-Nitrogen Cubanes and Protonated Polynitrogen Cations

Energy generation and storage are at the center of modern civilization. Energetic materials constitute quite a large class of compounds with a high amount of stored chemical energy that can be released. We hereby use a combination of quantum chemistry methods to investigate feasibility and properties of carbon-nitrogen cubanes and multi-charged polynitrogen cations in the context of their synthesis and application as unprecedented energetic materials. We show that the stored energy increases gradually with the nitrogen content increase. Nitrogen-poor cubanes retain their stabilities in vacuum, even at elevated temperatures. Such molecules will be probably synthesized at some point. In turn, polynitrogen cations are highly unstable, except N8H+, despite they are isoelectronic to all-carbon cubane. Kinetic stability of the cation decays drastically as its total charge increases. High-level thermodynamic calculations revealed that large amounts of energy are liberated upon decompositions of polynitrogen cations, which produce molecular nitrogen, acetylene, and protons. The present results bring a substantial insights to the design of novel high energy compounds.

cond-mat.mtrl-sci↗

arXiv2015

Solvation of the Morpholinium Cation in Acetonitrile. Effect of an Anion

Ionic liquids constitute a fast growing class of compounds finding multiple applications in science and technology. Morpholinium-based ionic liquids (MBILs) and their mixtures with polar molecular co-solvents are interesting as sustainable electrolyte systems for electrochemistry. We investigate local structures of protic and propton-free morpholinium cations in acetonitrile (ACN) using semi-empirical molecular dynamics (MD) simulations. An impact of an anion (acetate) on the cation solvation regularities is discussed. Unlike oxygen, nitrogen of the morpholine ring is a strong electrophilic binding center. This site is responsible for the interactions of the cation with the solvent and with the anion. In protic MBILs, the role of nitrogen is delegated to the proton, which is linked to nitrogen. The acetate anion weakens solvation of the cation due to occupation of space near nitrogen or proton. The analysis reveals a favorable solvation of MBILs in ACN, which is a prerequisite for a new high-performance electrolyte system. The reported structural data are validated through a point-to-point comparison with the MP2 post-Hartree-Fock theory.

cond-mat.mtrl-sci↗

arXiv2014

Global Minimum Search via Annealing. Nanoscale Gold Clusters

Global minimum potential energy state can be very challenging to locate in a relatively large atomistic system. Our present work investigates this problem using an example of gold nanoclusters, Au10, Au20, Au30, Au50. Nanoscale gold particles (NGPs) contribute heavily life sciences through their applications in diagnostics and therapeutics. NGPs feature manifold atomistic configurations depending on the conditions of synthesis. We apply annealing molecular dynamics (AMD) as an alternative and supplement to the well-established eigenfollowing (EF) geometry optimization. We conclude that the combination of AMD and EF systematically works more efficiently than EF alone.

cond-mat.mtrl-sci↗