17.3: First‐Principles Study on Secondary Electron Emission of MgO (200) and (111) Surfaces

Dai, Kai; Yan, Tao; Yang, Lanlan; Li, Qiaofen; Tolner, Harm

doi:10.1002/j.2168-0159.2014.tb00058.x

Cited by 3 publications

(3 citation statements)

References 9 publications

(8 reference statements)

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“…If we consider that the electronic transport in a plastic is noticeably different compared to that in a metallic system, these data are, to some extent, unexpected. Anyway, our results are consistent with other computational works on insulating materials [14,23].…”

Section: Discussionsupporting

confidence: 93%

“…Even though we found no experimental comparison of SEY for polyethylene, our result with the Ar + ion (γ N = 0.2204) is, at least, comparable with Hagstrum's theoretical analysis performed considering Ge (1 1 1) [27] (reproduced by computational modelling in [28]) and the numerical results of [14,23] for pure and defective MgO.…”

Section: Introductionsupporting

confidence: 81%

“…Our theoretical study of secondary electron emission has started considering a metal surface, and that's because, for similar systems, this subject has a fairly rich literature to refer to [1,13,19,20]. To the best of the authors' knowledge, the secondary emission properties of insulating metal oxides such as MgO have been largely studied both with an experimental [15,21,22] and a theoretical/computational approach [14,18,23,24]. However, this is not valid for all polymeric materials.…”

Section: Introductionmentioning

confidence: 99%

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First-principles evaluation of the secondary electron yield (γ^N) from polyethylene surface

Buccella

Ceresoli

Villa

et al. 2020

J. Phys. D: Appl. Phys.

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We have performed first-principles calculations (DFT) to estimate the secondary emission yield (SEY) through Auger neutralization mechanism (γ N ) related to the impact of a series of ions on a polyethylene surface. We have considered many relevant ionic species, such as Ar + , which is often used as a benchmark. Our main goal is to study dielectric surfaces but, to check the validity of our approach, we have also considered some metallic surfaces (Al, Cu, Cu:N, Cu:O and CuO) on which some more experimental data can be found. On the contrary, very few references are available regarding the Auger neutralization on insulating materials and, in particular, on polyethylene.The SEY outcomes for metals have basically reproduced the experimental references. In particular, the same decrease in γ N , which has been associated to a 'dirty' (gas-exposed) metal surface, was confirmed by calculations. Thus, the applicability of the method to plastic material was considered to give realistic results. The computed γ N values associated to polyethylene are in the order of 10 −1 for most of the ionic species here considered. Moreover, we have observed that a few percentage points of variations of the surface energy levels predicted by DFT calculations, may cause, depending on the ion type, a substantial change of γ N . Therefore a detailed sensitivity analysis has been included to address this problem. The results associated to metals have shown that γ N variations are, for some types of ions, very sharp, while this variability is milder for a polyethylene surface.Our calculations are fully compatible with the previous relevant literature and suggest that plastic materials are characterized by γ N coefficients similar to those of metals only slightly smaller.

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Section: Discussionsupporting

confidence: 93%

Section: Introductionsupporting

confidence: 81%

Section: Introductionmentioning

confidence: 99%

See 1 more Smart Citation

First-principles evaluation of the secondary electron yield (γ^N) from polyethylene surface

Buccella

Ceresoli

Villa

et al. 2020

J. Phys. D: Appl. Phys.

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Electronic transport in metal-molecular nanoelectronic networks: A density functional theory study

2019

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Electronic transport properties of nanoscale networks composed of interconnected molecules/gold nanoclusters are examined via first-principles plane wave scattering density functional theory-based simulations. Au-molecular (benzene/alkanedithiol) junctions and networks, connected in linear chains and Y-, H- and ring-shaped networks were studied. Molecular orbital calculations show HOMO (highest-occupied-molecular-orbital)-LUMO (lowest-unoccupied-molecular-orbital) gaps of chains decreased with length, indicating decreased barrier to electron transport. Orbitals near the gap of benzenedithiol networks show good delocalization whereas those of alkanedithiol molecules were more localized the metallic clusters. The transmission spectra of benzenedithiol-based networks showed increase in number/width of peaks near the Fermi energy as structures were extended due to increased orbital overlapping (spatially/energetically) with each other leading to formation of transmission pathways and electronic energy band-like properties. In contrast, lower transmission was observed for networks having localized orbitals (alkanedithiol molecular networks) with less overlap near the Fermi energy. Transmission spectra were also in good agreement with associated peaks in electronic density of states. In the case of multi-terminal networks, the location of delocalized orbitals can also shift from one branch to another, indicating potential ON/OFF switching behavior is possible. Switching elements and molecular-scale circuits (e.g., logic gates or inverters) based on Y- and H-shaped networks are proposed in analogy to electron waveguide devices and our simulations indicated that low-energy switching operation on the order of 10-50 meV may be possible. These nanoscale molecular electronic networks linked via metallic clusters provide an avenue for engineering electronics at the molecular level by using superstructures of different organic molecules and topologies.

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Методика Розрахунку Процесу Концентрування Харчових Розчинів Та Екстрактів У Мікрохвильовому Вакуум-Випарному Апараті

Ружицька¹,

Різниченко²,

Войтенко³

2018

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Для інтенсифікації процесу вакуум-випарювання запропоновано забезпечити рівномірність енергопідведення і виключити проміжний теплоносій за рахунок використання мікрохвильових технологій. При мікрохвильовому підведенні енергія надходить безпосередньо до молекул води в продукті, осередки пароутворення виникають у всьому об’ємі і виконують функцію гріючої поверхні. В результаті експериментального моделювання процесу мікрохвильового вакуум-випарювання розчинів цукру одержано коефіцієнти критеріального рівняння процесу.Наведено методику розрахунку процесу вакуум-випарювання в умовах дії мікрохвильового поля. В основі методики розрахунку критеріальне рівняння процесу випарювання в умовах вакууму та мікрохвильового енергопідведення, змінними якого є число енергетичної дії, безрозмірний параметр площі дзеркала продукту та безрозмірний тиск. Алгоритм включає розрахунки теплофізичних властивостей продукту, геометричних характеристик ємності, швидкості видалення вологи, поточну концентрацію сухих речовин у розчині, необхідну тривалість процесу, витрати енергії та економічні характеристики. Цикли розрахунку повторюються поки концентрація розчину в апараті сягне заданого для кінцевого продукту значення. Наведено результати перевірки запропонованої методики для розчинів цукру, кави, стевії. Встановлено, що відносна похибка для визначеної за алгоритмом швидкості видалення вологи відносно експерименту для розчинів цукру, стевії та кави складає 0,2…12 %.На основі розробленого мікрохвильового вакуум-випарного апарату запропоновано технологію одержання рідкого концентрату стевії – природного цукрозамінника. Екстракт стевії, який направляється на концентрування, одержується у мікрохвильовому екстракторі,а концентрація сухих речовин у кінцевому продукті - близько 12 %. For vacuum-vaporization process intensification it is offered to provide energy supply uniformity and exclude intermediate heat medium by using of microwave technologies. While microwave supply energy comes directly to water molecules in product, vaporization centers appear in whole volume and perform function of heating surface.As a result of experimental modeling of sugar solutions microwave vacuum vaporization the constants of criterion equation are received.The method of calculation of vacuum vaporization under microwave action is given. The base of the calculation method is criterion equation of vaporization under vacuum and microwave energy supply conditions, which variables are energy action criterion, dimensionless parameter of product mirror area and dimensionless pressure. The algorithm includes calculations of product thermophysical properties, vessel geometrical characteristics, water removing velocity, current dry matter concentration, necessary process duration, energy consumption and economical characteristics. Calculation cycles repeat until solution concentration in apparatus reaches the value prescribed for the final product. The results of verification of proposed method for sugar solutions, coffe and stevia extracts are given. It is defined, that relative error for calculated water removing velocity relatively to experiment for sugar, coffee and stevia solutions is 0,2…12 %.On the base of elaborated microwave vacuum evaporation apparatus a technology of production liquid stevia concentrate, a natural sugar substitute, is offered. Stevia extract that is being concentrated is received in microwave extractor. Dry matter concentration in final product is about 12 %.

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17.3: First‐Principles Study on Secondary Electron Emission of MgO (200) and (111) Surfaces

Cited by 3 publications

References 9 publications

First-principles evaluation of the secondary electron yield (γ^N) from polyethylene surface

First-principles evaluation of the secondary electron yield (γ^N) from polyethylene surface

Electronic transport in metal-molecular nanoelectronic networks: A density functional theory study

Методика Розрахунку Процесу Концентрування Харчових Розчинів Та Екстрактів У Мікрохвильовому Вакуум-Випарному Апараті

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17.3: First‐Principles Study on Secondary Electron Emission of MgO (200) and (111) Surfaces

Cited by 3 publications

References 9 publications

First-principles evaluation of the secondary electron yield (γ N ) from polyethylene surface

First-principles evaluation of the secondary electron yield (γ N ) from polyethylene surface

Electronic transport in metal-molecular nanoelectronic networks: A density functional theory study

Методика Розрахунку Процесу Концентрування Харчових Розчинів Та Екстрактів У Мікрохвильовому Вакуум-Випарному Апараті

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First-principles evaluation of the secondary electron yield (γ^N) from polyethylene surface

First-principles evaluation of the secondary electron yield (γ^N) from polyethylene surface