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3. The structure of the logistics supply chains of the EU countries in the context of the Covid-19 pandemic.

Author

Nekrasov, K. V.

Subjects
*COVID-19 pandemic, *SUPPLY chains, *ECONOMIC stabilization, *TRANSPORTATION industry, *LOGISTICS, *COVID-19
Abstract

The article shows that the crisis phenomena taking place in the world have an impact on many socio-economic processes. The scale of these negative consequences affected not only the local markets of countries, but also made significant adjustments to the existing economic relations in supply chains and their structure on a global scale. The analysis of the current situation is based on reports and statistics from the European Union and the World Bank. An assessment of the sectors of the EU transport sector and the change in their share of participation in trade and economic relations of the EU member states during the COVID-19 pandemic was made. The main directions for overcoming the crisis were offered. [ABSTRACT FROM AUTHOR]

Published
2023
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4. Investigation of cation self-diffusion mechanisms in UO2+-x using molecular dynamics

Author

Boyarchenkov, A. S., Potashnikov, S. I., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
Condensed Matter - Materials Science, Physics - Atomic and Molecular Clusters, Physics - Chemical Physics
Abstract

This article is devoted to investigation of cation self-diffusion mechanisms, taking place in UO2, UO2+x, and UO2-x crystals simulated under periodic (PBC) and isolated (IBC) boundary conditions using the method of molecular dynamics in the approximation of rigid ions and pair interactions. It is shown that under PBC the cations diffuse via an exchange mechanism (with the formation of Frenkel defects) with activation energy of 15-22 eV, while under IBC there is competition between the exchange and vacancy (via Schottky defects) diffusion mechanisms, which give the effective activation energy of 11-13 eV near the melting temperature of the simulated UO2.00 nanocrystals. Vacancy diffusion with lower activation energy of 6-7 eV was dominant in the non-stoichiometric crystals UO2.10, UO2.15 and UO1.85. Observations showed that a cation vacancy is accompanied by different number of anion vacancies depending on the deviation from stoichiometry: no vacancies in UO2.15, single vacancy in UO2.00 and four vacancies in UO1.85. The corresponding law of mass action formulas derived within the Lidiard-Matzke model allowed explaining the obtained activation energies and predicting a change in the activation energy within the temperature range of the superionic phase transition. The diffusion of cations on the surface of nanocrystals had activation energy of 3.1-3.6 eV., Comment: 22 pages, 6 tables, 15 figures

Published
2013
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5. High-precision molecular dynamics simulation of UO2-PuO2: Anion self-diffusion in UO2

Author

Potashnikov, S. I., Boyarchenkov, A. S., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Our series of articles is devoted to high-precision molecular dynamics simulation of mixed actinide-oxide (MOX) fuel in the approximation of rigid ions and pair interactions (RIPI) using high-performance graphics processors (GPU). In this article we study self-diffusion mechanisms of oxygen anions in uranium dioxide (UO2) with the ten recent and widely used sets of interatomic pair potentials (SPP) under periodic (PBC) and isolated (IBC) boundary conditions. Wide range of measured diffusion coefficients (from 10^-3 cm^2/s at melting point down to 10^-12 cm^2/s at 1400 K) made possible a direct comparison (without extrapolation) of the simulation results with the experimental data, which have been known only at low temperatures (T < 1500 K). A highly detailed (with the temperature step of 1 K) calculation of the diffusion coefficient allowed us to plot temperature dependences of the diffusion activation energy and its derivative, both of which show a wide (~1000 K) superionic transition region confirming the broad lambda-peaks of heat capacity obtained by us earlier. It is shown that regardless of SPP the anion self-diffusion in model crystals without surface or artificially embedded defects goes on via exchange mechanism, rather than interstitial or vacancy mechanisms suggested by the previous works. The activation energy of exchange diffusion turned out to coincide with the anti-Frenkel defect formation energy calculated by the lattice statics., Comment: 18 pages, 11 figures, 5 tables

Published
2012
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6. Molecular dynamics simulation of UO2 nanocrystals melting under isolated and periodic boundary conditions

Author

Boyarchenkov, A. S., Potashnikov, S. I., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Melting of uranium dioxide (UO2) nanocrystals has been studied by molecular dynamics (MD) simulation. Ten recent and widely used sets of pair potentials were assessed in the rigid ion approximation. Both isolated (in vacuum) and periodic boundary conditions (PBC) were explored. Using barostat under PBC the pressure dependences of melting point were obtained. These curves intersected zero near -20 GPa, saturated near 25 GPa and increased nonlinearly in between. Using simulation of surface under isolated boundary conditions (IBC) recommended melting temperature and density jump were successfully reproduced. However, the heat of fusion is still underestimated. These melting characteristics were calculated for nanocrystals of cubic shape in the range of 768-49 152 particles (volume range of 10-1000 nm^3). The obtained reciprocal size dependences decreased nonlinearly. Linear and parabolic extrapolations to macroscopic values are considered. The parabolic one is found to be better suited for analysis of the data on temperature and heat of melting., Comment: 19 pages, 15 figures, 4 tables

Published
2011
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7. Molecular dynamics simulation of UO2 nanocrystals surface

Author

Boyarchenkov, A. S., Potashnikov, S. I., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

In this article we investigated surface of nanocrystals (NC) of uranium dioxide (UO2) using molecular dynamics (MD) under isolated (non-periodic) boundary conditions with the approximation of pair potentials and rigid ions. It is shown that a cubic shape of the model NCs is metastable and the stable equilibrium is reached in the process of structural relaxation to the octahedral shape over a time of 1000 ns (200 million MD steps), which increases with the size of NC. We measured the size dependences of the lattice parameter and the surface energy density for NC of cubic and octahedral shape with volume up to 1000 nm3 (50000 particles) at temperatures of 2200K and 2300K. For the surfaces {100} and {111} we obtained the energy density {\sigma}100=1.602\pm0.016 J/m^2, {\sigma}111=1.137\pm0.032 J/m^2 and surface tension constant {\gamma}111=0.875\pm0.008 J/m^2. The resulting ratio of {\sigma}100/{\sigma}111=1.408\pm0.042 within the error coincides with the experimental value of 1.42\pm0.05 measured for microscopic cavities in monocrystals of UO2., Comment: 11 pages, 8 figures, 5 tables

Published
2011
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8. High-precision molecular dynamics simulation of UO2-PuO2: superionic transition in uranium dioxide

Author

Potashnikov, S. I., Boyarchenkov, A. S., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Our series of articles is devoted to high-precision molecular dynamics simulation of mixed actinide-oxide (MOX) fuel in the rigid ions approximation using high-performance graphics processors (GPU). In this article we assess the 10 most relevant interatomic sets of pair potential (SPP) by reproduction of the Bredig superionic phase transition (anion sublattice premelting) in uranium dioxide. The measurements carried out in a wide temperature range from 300K up to melting point with 1K accuracy allowed reliable detection of this phase transition with each SPP. The {\lambda}-peaks obtained are smoother and wider than it was assumed previously. In addition, for the first time a pressure dependence of the {\lambda}-peak characteristics was measured, in a range from -5 GPa to 5 GPa its amplitudes had parabolic plot and temperatures had linear (that is similar to the Clausius-Clapeyron equation for melting temperature)., Comment: 7 pages, 6 figures, 1 table

Published
2011
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9. High-precision molecular dynamics simulation of UO2-PuO2: pair potentials comparison in UO2

Author

Potashnikov, S. I., Boyarchenkov, A. S., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
Condensed Matter - Materials Science, Physics - Chemical Physics
Abstract

Our series of articles is devoted to high-precision molecular dynamics simulation of mixed actinide-oxide (MOX) fuel in the approximation of rigid ions and pair interactions (RIPI) using high-performance graphics processors (GPU). In this first article 10 most recent and widely used interatomic sets of pair potentials (SPP) are assessed by reproduction of solid phase properties of uranium dioxide (UO2) - temperature dependences of the lattice constant, bulk modulus, enthalpy and heat capacity. Measurements were performed with 1K accuracy in a wide temperature range from 300K up to melting points. The best results are demonstrated by two recent SPPs MOX-07 and Yakub-09, which both had been fitted to the recommended thermal expansion in the range of temperatures 300-3100K. They reproduce the experimental data better than the widely used SPPs Basak-03 and Morelon-03 at temperatures above 2500K., Comment: 11 pages, 9 figures, 4 tables

Published
2011
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10. Competitiveness based on logistics and supply chain in medical device industry during the Covid-19 period in Indonesia.

Author

Maemunah, S. and Nekrasov, K.

Subjects
*COVID-19 pandemic, *MEDICAL equipment, *MEDICAL supplies, *SUPPLY chains, *INFORMATION technology, *PERFORMANCE technology
Abstract

This study is about the influence of supply chain business strategy, logistics performance and information technology performance on the competitiveness of the medical device industry. The results obtained are that the supply chain business strategy has a direct effect on logistics performance, information technology performance on the supply chain competitiveness of the medical device industry during the COVID-19 period in Indonesia. Data was obtained by distributing questionnaires to 248 respondents as samples. Analysed the data using a structural equation modelling (SEM) analysis tool. The findings show that business strategy has a positive and significant effect on logistics performance, information technology performance on the competitiveness of medical devices in Indonesia. Based on these findings, to improve and maintain competitiveness are investment, availability, quality of hardware and software infrastructure in information technology, customer satisfaction, good relations with suppliers and reacting quickly and appropriately in all logistics and supply chain activities to excel in front of competitor. Originality is the competitiveness of the supply chain is determined based on the assessment of experts in the supply chain. Further research can be expanded to include indicators such as ROA (return on assets), ROI (return on investment) and market share. [ABSTRACT FROM AUTHOR]

Published
2023
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16. A mechanism of cation diffusion in ThO2 nanocrystal bulk. A molecular dynamic simulation.

Author

Seitov, D. D., Pitskhelaury, S. S., Nekrasov, K. A., Boyarchenkov, A. S., and Kupryazhkin, A. Ya.

Subjects
DYNAMIC simulation, MOLECULAR dynamics, VACANCIES in crystals, FREE surfaces, CATIONS
Abstract

A molecular dynamics simulation of the self-diffusion of thorium cations in ThO2 nanocrystals with a free surface is conducted. It is shown that a vacancy in the bulk of a crystal initiates a complex collective movement of cations, in which the interstitial positions surrounding the vacancy are involved. The diffusion coefficients of cations in the temperature range are calculated. The effective activation energy of diffusion is ED = (7.6 ± 0.7) eV. [ABSTRACT FROM AUTHOR]

Published
2022
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17. IMPACT OF THE PANDEMIC ON THE STRUCTURE OF THE LOGISTIC SUPPLY CHAIN AND TRADE OF THE EUROPEAN UNION

Author

Allahverdiyeva, G. Z. kyzy and Nekrasov, K. V.

Subjects
ЛОГИСТИЧЕСКИЕ ТЕНДЕНЦИИ, ПАНДЕМИЯ, ЕВРОПЕЙСКИЙ СОЮЗ, LOGISTICS TRENDS, ECONOMY, ЭКОНОМИКА, PANDEMIC, EUROPEAN UNION
Abstract

This article focuses on the most relevant topics for the period 2019-2021 - the coronavirus pandemic. The pandemic in this article is the subject of influence on large areas, which are considered in the article-logistics and economics (using the example of the European Union). The importance of logistics as one of the key sectors of the world economy is determined. Attention is paid to the problems of the studied directions and the main development trends. Using available sources of information, the main indicators of industry performance are considered. Their dynamics and rates of change are determined. В данной статье уделяется внимание наиболее актуализированной тематике на период 2019-2021 годов- пандемии коронавируса. Пандемия в данной статье выступает предметом влияния на крупные направления, которые и рассматриваются в статье-логистика и экономика (на примере Европейского союза). Определяется значимость логистики как одного из ключевых секторов мировой экономики. Обращается внимание на проблематику изучаемых направлений и основные тенденции развития. Используя доступные источники информации, рассматриваются основные показатели деятельности отраслей. Определяются их динамика и темпы изменения.

Published
2021

21. BRAF status in сito-morphological diagnosis of thyroid nodules

Author

Tarashchenko, Yu. M., Kovalenko, A. Ye., Ostafiichuk, M. V., and Nekrasov, K. A.

Subjects
хірургічне лікування, мутация BRAF V600E, щитоподібна залоза, endocrine system diseases, тонкоигольная аспирационная пункционная биопсия, papillary thyroid, surgical treatment, BRAF V600E mutation, мутація BRAF V600E, digestive system diseases, тонкоголкова аспіраційна пункційна біопсія, хирургическое лечение, карцинома, fine needle aspiration biopsy, cancer, щитовидная железа, neoplasms
Abstract

The aim of study – to determine the significance of the BRAF V600E mutation presence in the cytomorphological diagnosis of thyroid nodules.Materials and methods. The study included 65 patients requiring surgical treatment for thyroid nodular pathology. Material to determine the BRAF V600E mutation was taken by means of a fine needle aspiration biopsy before surgery. The BRAF V600E mutation was detected by real-time PCR analysis.Results. A pathomorphological study of the removed thyroid nodules showed that all 22 benign nodules were BRAF-negative. Among the 43 papillary thyroid cancer only 20 were BRAF-positive (46.5 %). BRAF mutations were found more often (P < 0.001) in patients with classical and oxyphilic cell papillary thyroid cancer (60 % and 100 %, respectively) than in patients with follicular variant of PTC (6.7 %). Locally invasive tumors were more often BRAF-negative cases (P < 0.05) than non-invasive tumors and amounted to 75.0 % and 37.5 %, respectively. But, when comparing the morphological variant and invasive properties of the tumor, it was found that all cases of the follicular variant of the PC had signs of invasion and were significantly more often observed (P < 0.01) compared with the classical and oxyphilic cell variants. The BRAF V600E mutation was observed both in tumors with metastasis to the regional lymph nodes (55.0 %) and in tumors without metastases (37.5 %), with no significant difference.Conclusions. The presence of the BRAF V600E mutation is a diagnostic marker for papillary thyroid carcinoma, and its detection confirms the presence of malignancy. BRAF positive carcinomas were in 46.5 % of cases. The combination of BRAF-negative and the cytology of groups V and VI by Bethesda may indicate about a follicular variant of PTC. An increase in the number of molecular genetic markers in the preoperative diagnosis of thyroid cancer can significantly improve the quality of diagnosis and surgical treatment., Цель работы – определение значимости наличии мутации BRAF V600E в цитоморфологической диагностике тиреоидных узлов.Материалы и методы. В исследование включены 65 пациентов, нуждающихся в хирургическом лечении по поводу узловой патологии щитовидной железы (ЩЖ). Материал для определения мутации BRAF V600E брали путем тонкоигольной пункционной аспирационной биопсии на дооперационном этапе. Мутацию BRAF V600E определяли путем проведения анализа методом ПЦР в режиме реального времени.Результаты. Окончательное морфологическое исследование удаленных узлов показало отсутствие BRAF-мутаций во всех 22 доброкачественных узлах. Среди 43 папиллярных карцином (ПК) BRAF-положительными были 20 (46,5 %).BRAF-мутации достоверно чаще (p < 0,001) обнаружены у пациентов с классическим и оксифильноклеточным вариантами папиллярной карциномы (60 % и 100 % соответственно) по сравнению с фолликулярным вариантом (6,7 %). При оценке инвазивности опухолей обнаружено, что среди локально инвазивных ПК щитовидной железы достоверно чаще преобладали BRAF-отрицательные случаи (p < 0,05) над неинвазивными ПК (75,0 % и 37,5 % соответственно). В ходе анализа инвазивности опухоли и морфологического варианта установлено, что все случаи фолликулярного варианта ПК имели признаки инвазии, их достоверно чаще отмечали (p < 0,01) по сравнению с классическим и оксифильноклеточным вариантами. Мутация BRAF V600E обнаружена и в опухолях с метастазированием в регионарные лимфатические узлы шеи (55,0 %), и в опухолях без метастазов (37,5 %), без вероятной разницы.Выводы. Наличие мутации гена BRAF V600E – диагностический маркер папиллярной карциномы щитовидной железы, и ее установление подтверждает наличие злокачественности. BRAF-положительные карциномы отмечены в 46,5 % наблюдений. Отсутствие мутации гена BRAF V600E в сочетании с цитологическим заключением V и VI групп по Bethesda может свидетельствовать о наличии фолликулярного варианта ПК. Расширение количества молекулярно-генетических маркеров в дооперационный диагностике рака щитовидной железы может значительно улучшить качество диагностики и хирургического лечения., Мета роботи – визначення значущості наявності мутації BRAF V600E в цитоморфологічній діагностиці тиреоїдних вузлів.Матеріали та методи. У дослідження залучили 65 пацієнтів, які потребували хірургічного лікування з приводу вузлової патології щитоподібної залози (ЩЗ). Матеріал для визначення мутації BRAF V600E брали шляхом тонкоголкової пункційної аспіраційної біопсії на доопераційному етапі. Мутацію BRAF V600E визначали шляхом здійснення аналізу методом ПЛР у режимі реального часу.Результати. Остаточне морфологічне дослідження видалених вузлів показало відсутність BRAF-мутацій у всіх 22 доброякісних вузлах. Серед патогістологічно підтверджених 43 папілярних карцином (ПК) BRAF-позитивними були 20 (46,5 %).Аналізуючи наявність генетичних мутацій залежно від підтипів папілярних карцином ЩЗ, виявили: BRAF-мутації достовірно частіше (p < 0,001) визначали у пацієнтів із класичним та оксифільноклітинним варіантами папілярної карциноми (60 % і 100 % відповідно) порівняно з фолікулярним варіантом папілярної карциноми ЩЗ (6,7 %). Оцінюючи інвазивність пухлин, встановили, що серед локально інвазивних ПК ЩЗ вірогідно частіше переважали BRAF-негативні випадки (p < 0,05) над неінвазивними ПК (75,0 % і 37,5 % відповідно). Під час аналізу інвазивності пухлини залежно від її морфологічного варіанта виявили, що всі випадки фолікулярного варіанта ПК мали ознаки інвазії, їх вірогідно частіше визначали (p < 0,01) порівняно з класичним та оксифільноклітинними варіантами. Мутація BRAF V600E встановлена і в пухлинах із метастазуванням у реґіонарні лімфатичні вузли шиї (55,0 %), і в пухлинах без метастазів (37,5 %) без вірогідної різниці. Висновки. Наявність мутації гена BRAF V600E – діагностичний маркер папілярної карциноми щитоподібної залози, його виявлення підтверджує наявність злоякісності. BRAF-позитивні карциноми виявили в 46,5 % спостережень. Відсутність мутації гена BRAFV600E в поєднанні з цитологічними висновками груп V і VI за Bethesda може свідчити про наявність фолікулярного варіанта ПК. Розширення кількості молекулярно-генетичних маркерів у доопераційній діагностиці раку ЩЗ може значно поліпшити якість діагностики та хірургічного лікування.

Published
2020

23. Single-stage plasma-arc synthesis of metallo-endofullerences

Author

Gerasimov, V. I., Kalinin, G. V., Nikonov, Yu. A., Titovets, Yu. F., Kalabushkin, A. E., Alekhin, O. S., Nekrasov, K. V., Rusetskaya, S. N., Arapov, O. V., Alekseev, N. I., Kustova, E. V., Lishchuk, V. V., Pleshkov, M. A., Semenov, K. N., Keskinov, V. A., and Charykov, N. A.

Published
2007
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24. THE INTERPARTICLE POTENTIALS FOR MOLECULAR DYNAMIC SIMULATION OF THE IMPACT OF COLLISION CASCADES ON GAS BUBBLES IN PLUTONIUM DIOXIDE

Author

Seitov, D. D., Pitskhelaury, S. S., Nekrasov, K. A., Kupryazhkin, A. Ya., and Пицхелаури, С. C.

Abstract

The influence of interaction potentials choice on the molecular dynamics simulation of radiogenic gas bubble resolution under the collision cascades impact in PuO2 crystal is studied. This choice is shown to fundamentally affect the amount of energy transferred to a bubble from the fast particles. Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 19-32-90274.

Published
2020

25. A MOLECULAR DYNAMICS SIMULATION OF URANIUM CARBONITRIDE CRYSTALS USING A MODIFIED EMBEDDED ATOM MODEL METHOD

Author

Pitskhelaury, S. S., Seitov, D. D., Nekrasov, K. A., Gupta, S. K., and Пицхелаури, С. C.

Abstract

A molecular dynamic simulation of uranium carbonitrides is carried out. Parameters and potentials for dynamic variation of particle charges are proposed. The lattice constant, bulk modulus, heat capacity dependences on temperature and the melting points are determined in the framework of the model. Исследование выполнено при финансовой поддержке РФФИ в рамках научного про-екта №16-52-48008 ИНД_оми. С.К. Гупта также благодарит Департамент науки и технологии (Индия) и РФФИ за поддержку по гранту INT/RUS/RFBR/IDIR/P-6/2016.

Published
2020

26. HELIUM DIFFUSION ALONG A RING DISLOCATION IN URANIUM DIOXIDE. A MOLECULAR DYNAMICS SIMULATION

Author

Shekunov, G. S. and Nekrasov, K. A.

Abstract

A simulation of helium migration along a ring dislocation in uranium dioxide is done. Two sets of He interaction potentials are compared, fundamentally differing in the strength of binding of the atom to uranium ions. Helium diffusion coefficients are obtained at temperatures from 375 to 1000 K. Исследование выполнено при финансовой поддержке РФФИ в рамках научного проекта № 16-52-48008 ИНД_оми.

Published
2020

43. Fuel loading optimization into the active zone of the BN-800 reactor for the purpose of the most balanced distribution of the energy releasing field

Author

Osanova, E. R. and Nekrasov, K. A.

Abstract

During the research, the optimization of fuel loading into the active zone of the BN-800 reactor was conducted using the simplest method by the mass of fissile material without the possibility of installing different types of fuel in one zone. The simulation was carried out in the software-hardware complex GEFEST-800.

Published
2019

44. Ab-initio calculations of CO2 adsorption on nonpolar (100) ZnO surface

Author

Usseinov, A., Akilbekov, A., Dauletbekova, A., Geniyatova, Sh., Soltanbek, N., Nekrasov, K., and Seitov, D.

Subjects
Condensed Matter::Materials Science, Physics::Chemical Physics
Abstract

In this paper, the ab-initio calculations of the CO2 molecule adsorption on the nonpolar ZnO surface were carried out in order to find the equilibrium configuration of the adsorbed molecule, as well as we studied the effect of impurity concentration and the presence of native point defects onto binding energy of molecule. Also, the potential for-mation of a new molecular complex is considered. All results were compared with known experimental data.

Published
2019

47. Molecular Dynamic Simulation of Helium Diffusion in Ring Dislocation in UO2 Nanocrystal.

Author

Shekunov, G. S., Nekrasov, K. A., and Gupta, S. K.

Subjects
*DYNAMIC simulation, *HELIUM atom, *HELIUM, *DIFFUSION, *DIFFUSION processes
Abstract

Molecular dynamic simulation of helium diffusion within a ring dislocation inside stoichiometric UO2 nanocrystal was carried out. During the computational experiments (2.7 ns) in the temperature range from 525 to 1000 K, the dislocation was stable and the helium atom was contained inside the dislocation core. The magnitudes of the diffusion coefficient varied from 4.1·10–6 to 6.6·10–5 cm²/s. The diffusion process could be characterized by the constant activation energy ED = (0.25 ± 0.05) eV. [ABSTRACT FROM AUTHOR]

Published
2019
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48. Energetic Stability and Tuned Electronic Properties of Boron-Doped Carbon Phosphide Monolayer.

Author

Kansara, Shivam, Gupta, Sanjeev K., Sonvane, Yogesh, and Nekrasov, K. A.

Subjects
MONOMOLECULAR films, DENSITY functionals, DYNAMIC stability, CHARGE carrier mobility, ELECTRIC fields, ELECTRONIC equipment
Abstract

We have investigated two-dimensional (2D) monolayer structures composed of p-group binary elements. Here, we have focused on the dynamic stability and bandgap tuning of novel boron (B) doped carbon phosphide (CP) monolayer by implementing external perpendicular electric fields to the layer using ab initio method based on density functionals theory (DFT). First, we have optimized boron doped CP monolayer and analyzed direct band gap 0.65 eV at M-point. With increasing of the applied electric fields for ±0.5 V/Å to ±1.5 V/Å; the bandgap continuously decreases up to metallic nature. The low effective mass is showing the high carrier mobility. The changing to the atomic distance and corresponding charges could be responsible to the semiconductor to metal behavior. This study is relevant for the fabrication of novel electronic and photonic devices. [ABSTRACT FROM AUTHOR]

Published
2019
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49. Electronic Structure of ZnO/CdX (X= S, Se, Te) Core/Shell Nanowires: DFT Study.

Author

Shukla, Rishit S., Gupta, Sanjeev K., Gajjar, P. N., Nekrasov, K. A., and Kupryazhkin, A. Ya.

Subjects
ELECTRONIC structure, NANOWIRE devices, ELECTRONIC band structure, NANOWIRES, FERMI level, VALENCE bands, TELLURIUM
Abstract

A density functional theory (DFT) based computation was conducted to study the electronic band structure, electron density of states (DOS) and partial DOS of ZnO/CdX core/shell nanowires (NWs), where X= S, Se, Te. The band structures calculations show a direct band gap of approximately 1.555 eV, 1.167 eV and 0.833 eV for ZnO/CdS, ZnO/CdSe and ZnO/CdTe, respectively at Γ-point, using generalized gradient approximation (GGA). The TDOS and PDOS calculations predict that a sharp peak is obtained at -9 eV below the Fermi level, in the valence band (VB) due to the possible hybridization between Zn-s, O-p and X-p orbitals. Also, it was observed that the contributions to the total DOS at the conduction band (CB) are mainly dominated by Zn-s and Cd-s orbitals, hinting at possible strong hybridization between them. Also, the low band gaps of ZnO/CdSe and ZnO/CdTe NWs predict the opacity of these NWs at room temperatures while the relatively high band gap of ZnO/CdS NW could suggest their use in fabrication of high operating voltage devices. Our conjecture hint at the applications of these NWs in devices where selective absorbance is a desired characteristic. [ABSTRACT FROM AUTHOR]

Published
2019
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50. The first principles calculations of CO2 adsorption on (101̅0 ) ZnO surface.

Author

Usseinov, A. B., Akilbekov, A. T., Kotomin, E. A., Popov, A. I., Seitov, D. D., Nekrasov, K. A., Giniyatova, Sh. G., and Karipbayev, Zh. T.

Subjects
BINDING energy, SURFACE defects, ADSORPTION (Chemistry), GAS mixtures, CARBON dioxide, ZINC oxide synthesis
Abstract

Atomistic understanding of the interaction between defects and active surface of the sensor is necessary for the developing devices detecting bio-and gas mixtures. We performed first principles computer simulations of the carbon dioxide (CO2) molecule adsorption on a ZnO surface in various configurations and location on the surface. It is shown that the tridentate configuration is the most energetically favorable, the binding energy of the molecule weakly depends on the surface coverage. The presence of intrinsic defects on the surface, such as an oxygen vacancy, leads to a small reduction of the binding energy. The observed data from the NEXAFS experiment and hypothetical formation of a new compound H2CO on the surface are discussed in the light of our calculations. [ABSTRACT FROM AUTHOR]

Published
2019
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