scholarly journals SIMULATION OF POLYMORPHIC VARIETIES OF HEXAGONAL GRAPHENE FUNCTIONALIZED BY HYDROXYL GROUPS

2021 ◽  
pp. 541-551
Author(s):  
Максим Евгеньевич Беленков ◽  
Владимир Михайлович Чернов
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Density Functional Theory Method ◽  
Hydroxyl Groups ◽  
Functional Theory ◽  
Graphene Layers ◽  
Sublimation Energy ◽  
The Density Functional Theory ◽  
Direct Band ◽  
Oxygen Bond

Моделирование кристаллической и электронной структуры слоев гексагонального графена, на поверхность которых были химически адсорбированы гидроксильные группы, было выполнено методом теории функционала плотности. В результате расчетов была установлена возможность устойчивого существования пяти структурных разновидностей COH - L слоев. Слоевая плотность изменяется от 1,62 до 1,72 мг/м. Длина водород-кислородной связи варьируется в диапазоне от 1,046 до 1,079 Å, а углерод-кислородной связи - от 1,455 до 1,465 Å. Ориентация O - H связей относительно плоскости слоев может варьироваться в зависимости от выбора элементарной ячейки слоя. Минимальной энергией сублимации и равной 18,69 эВ/(COH) обладает слой COH-L - T4, а максимальную энергию сублимации 18,93 эВ/(COH) имеет слой COH - L - T1. Электронная структура всех COH слоев характеризуется наличием прямой запрещенной зоны на уровне энергии Ферми, изменяющейся в диапазоне от 3,02 до 4,56 эВ. Computer simulation of the crystal and electronic structure of hexagonal graphene layers, on the surface of which hydroxyl groups, chemically adsorbed, was performed by the density functional theory method. As a result of calculations, the possibility of the stable existence of five structural varieties of COH - L layers was established. The layer density varies from 1,62 to 1,72 mg/m. The length of the hydrogen-oxygen bond varies in the range from 1,046 to 1,079 Å, and the carbon-oxygen bond-from 1,455 to 1,465 Å. The orientation of the -OH bonds relative to the surface of the layers can vary depending on the choice of the unit cell of the layer. Layer COH - L - T4 has the minimum sublimation energy equal to 18,69 eV/(COH), and layer COH - L - T1 has the maximum sublimation energy 18,93 eV/(COH). The electronic structure of all COH layers is characterized by the presence of a direct band gap at the Fermi energy level, varying in the range from 3,02 to 4,56 eV.

Ab Initio Calculations of New α-L5-7a and β-L5-7a Graphyne Polymorphic Varieties

2022 ◽  
Vol 1049 ◽  
pp. 180-185
Author(s):  
Viktor Mavrinskii ◽  
Evgeniy A. Belenkov
Keyword(s):  
Density Functional ◽  
Electronic States ◽  
Density Functional Theory Method ◽  
Geometric Optimization ◽  
Initial Structure ◽  
Functional Theory ◽  
Graphene Layers ◽  
Density Of Electronic States ◽  
Sublimation Energy ◽  
The Density Functional Theory

Calculations of the structural and energy parameters, band structure and density of electronic states of new structural varieties of graphyne have been performed by the density functional theory method. The initial structure of the nine polymorphs was theoretically constructed on the basis of the 5-7a graphene layer. As a result of the calculations, the structure of only five graphyne layers was found to be stable: α-L5-7a, β1-L5-7a, β2-L5-7a, β3-L5-7a and β4-L5-7a. The structure of layers γ1-L5-7a, γ2-L5-7a, and γ3-L5-7a is transformed into the structure of graphene layers by geometric optimization, and the graphyne layer γ4-L5-7a is transformed sp+sp2 layer L3-6-13. The sublimation energy of the stable graphyne polymorphs varies from 6.66 to 6.78 eV/atom. The density of electronic states at the Fermi energy level for all α-L5-7a and β-L5-7a layers of graphyne is different from zero, so the new graphyne polymorphs should have metallic properties.

Electronic Structure and Ionic Transport in Phosphate Glass with Pyrophosphate Structural Elements

2019 ◽  
Vol 822 ◽  
pp. 864-870 ◽  
Author(s):  
Andrey Petrov ◽  
Ivan Sokolov ◽  
Viktor A. Markov
Keyword(s):  
Electronic Structure ◽  
Density Functional ◽  
Density Functional Theory Method ◽  
Ionic Transport ◽  
Ab Initio Molecular Dynamics ◽  
Theory Method ◽  
Ideal Crystal ◽  
Structural Elements ◽  
Functional Theory ◽  
The Density Functional Theory

The electronic structure of lithium pyrophosphates (Li4P2O7) and sodium (Na4P2O7) was calculated by the density functional theory method. The calculations were performed for ordered (crystalline) and disordered (corresponding to glassy) structural states of lithium and sodium pyrophosphates. The disordering of the structure is simulated by ab initio molecular dynamics from crystal state with the same atomic basis as used for ideal crystal electronic calculations.

scholarly journals INVESTIGATION OF NEW POLYMORPHIC VARIETIES OF BORON NITRIDE WITH DIAMOND-LIKE STRUCTURES

2020 ◽  
pp. 493-503
Author(s):  
Дмитрий Сергеевич Ряшенцев ◽  
Евгений Анатольевич Беленков
Keyword(s):  
Density Functional Theory ◽  
Boron Nitride ◽  
Bulk Density ◽  
Density Functional ◽  
Theoretical Study ◽  
Density Functional Theory Method ◽  
Theory Method ◽  
Functional Theory ◽  
Sublimation Energy ◽  
The Density Functional Theory

В работе проведено теоретическое исследование новых полиморфных разновидностей нитрида бора, имеющих алмазоподобные структуры. В результате расчетов методом теории функционала плотности в градиентном приближении была установлена возможность устойчивого существования четырех новых структурных разновидностей нитрида бора: BN - LA4, BN - LA5, BN - LA6 и BN - LA7 . Энергия сублимации новых BN фаз варьируется в диапазоне от 16,85 до 17,84 эВ/(BN), ширина запрещенной зоны - от 4,34 до 6,07 эВ. Объемная плотность BN полиморфов изменяется от 3,020 до 3,452 г/см. The article presents a theoretical study of new polymorphic varieties of boron nitride with diamond-like structures. As a result of calculations by the density functional theory method in the gradient approximation, the possibility of stable existence of four new structural varieties of boron nitride: BN - LA4, BN - LA5 , BN - LA6, and BN - LA7 was established. The sublimation energy of new BN phases varies in the range from 16,85 to 17,84 eV/(BN), the band gap is from 4,34 to 6,07 eV. The bulk density of BN polymorphs varies from 3,020 to 3,452 g/cm.

scholarly journals AB INITIO CALCULATIONS OF THE CRYSTALLINE AND ELECTRONIC STRUCTURE OF 5-7 FLUOROGRAPHENE VARIETIES

2020 ◽  
pp. 326-337
Author(s):  
Максим Евгеньевич Беленков ◽  
Владимир Михайлович Чернов
Keyword(s):  
Density Functional ◽  
Density Functional Theory Method ◽  
Band Gaps ◽  
First Principle ◽  
Functional Theory ◽  
Graphene Layers ◽  
First Principle Calculations ◽  
Deformation Parameters ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties

Первопринципные расчеты структуры и электронных свойств двух новых полиморфных разновидностей фторографена были выполнены методом теории функционала плотности. Новые слои фторографена могут формироваться при химической адсорбции фтора на поверхности 5 - 7 графеновых слоев. Структура слоя первого типа более деформирована по сравнению со структурой второго типа (деформационные параметры Def = 60,48° и Def = 31,51° ). Энергии сублимации и ширины запрещенных зон составляют 13,85, 14,17 эВ/(CF), и 4,09, 3,32 эВ для CF - L слоев T1, T2 типов соответственно. First-principle calculations of the structural and electronic properties of two new polymorphic varieties of fluorographene were performed using the density functional theory method. New layers of fluorographene can be formed during chemical adsorption of fluorine on the surface of 5 - 7 graphene layers. The structure of the layer of the first type is more deformed in comparison with the structure of the second type (deformation parameters Def = 60,48 ° and Def = 31,51 °). Sublimation energies and band gaps are 13,85, 14,17 eV/(CF), and 4,09, 3,32 eV for CF-L layers of T1, T 2 types, respectively.

Structure and Properties of Diamond-Like Phases

2016 ◽  
Vol 845 ◽  
pp. 231-234 ◽  
Author(s):  
Vladimir Greshnyakov ◽  
Evgeniy A. Belenkov
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Structural Parameters ◽  
Three Dimensional ◽  
Density Functional Theory Method ◽  
Theory Method ◽  
Structure And Properties ◽  
Functional Theory ◽  
Graphene Layers ◽  
The Density Functional Theory

The geometrically optimized structures of twenty three carbon diamond-like phases obtained by linking graphene layers, carbon nanotubes, and three-dimensional graphites has been calculated using the density functional theory method and the structural parameters, densities, sublimation energies, electronic properties, and bulk moduli have been calculated.

Study of the Stability and Chemical Reactivity of a Series of Tetrazole Pyrimidine Hybrids by the Density Functional Theory Method (DFT)

2021 ◽  
Vol 37 (4) ◽  
pp. 805-812
Author(s):  
Ahissandonatien Ehouman ◽  
Adjoumanirodrigue Kouakou ◽  
Fatogoma Diarrassouba ◽  
Hakim Abdel Aziz Ouattara ◽  
Paulin Marius Niamien
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Molecular Descriptors ◽  
Chemical Reactivity ◽  
Density Functional Theory Method ◽  
Functional Theory ◽  
Reactivity Descriptors ◽  
The Density Functional Theory ◽  
The Stability ◽  
Global Reactivity Descriptors

Our theoretical study of stability and reactivity was carried out on six (06) molecules of a series of pyrimidine tetrazole hybrids (PTH) substituted with H, F, Cl, Br, OCH3 and CH3 atoms and groups of atoms using the density function theory (DFT). Analysis of the thermodynamic formation quantities confirmed the formation and existence of the series of molecules studied. Quantum chemical calculations at the B3LYP / 6-311G (d, p) level of theory determined molecular descriptors. Global reactivity descriptors were also determined and analyzed. Thus, the results showed that the compound PTH_1 is the most stable, and PTH_5 is the most reactive and nucleophilic. Similarly, the compound PTH_4 is the most electrophilic. The analysis of the local descriptors and the boundary molecular orbitals allowed us to identify the preferred atoms for electrophilic and nucleophilic attacks.

scholarly journals Oxygen vacancy and doping atom effect on electronic structure and optical properties of Cd2SnO4

RSC Advances ◽  
2018 ◽  
Vol 8 (2) ◽  
pp. 640-646 ◽  
Author(s):  
Mei Tang ◽  
JiaXiang Shang ◽  
Yue Zhang
Keyword(s):  
Optical Properties ◽  
Electronic Structure ◽  
Oxygen Vacancy ◽  
Density Functional ◽  
Generalized Gradient ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
La Doped ◽  
Doping Atom ◽  
Atom Effect

The electronic structure and optical properties of oxygen vacancy and La-doped Cd2SnO4 were calculated using the plane-wave-based pseudopotential method based on the density functional theory (DFT) within the generalized gradient approximation (GGA).

scholarly journals Practical and Theoretical Study on the Inhibitory Influences of New Azomethine Derivatives Containing an 8-Hydroxyquinoline Moiety for the Corrosion of Carbon Steel in 1 M HCl

2018 ◽  
Vol 34 (6) ◽  
pp. 3016-3029 ◽  
Author(s):  
A. El-Yaktini ◽  
A. Lachiri ◽  
M. El-Faydy ◽  
F. Benhiba ◽  
H. Zarrok ◽  
...  
Keyword(s):  
Carbon Steel ◽  
Density Functional ◽  
Electrochemical Impedance ◽  
Density Functional Theory Method ◽  
Steel Corrosion ◽  
Experimental Results ◽  
Chemical Parameters ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Inhibition Ability

The inhibition ability of a new Azomethine derivatives containing the 8-hydroxyquinoline (BDHQ and MDHQ) towards carbon steel corrosion in HCl solution was studied at various concentrations and temperatures using weight loss, polarization curves and electrochemical impedance spectroscopy (EIS) methods. The experimental results reveal that BDHQ and MDHQ are efficient mixed type corrosion inhibitors, and their inhibition efficiencies increase with increasing concentration. The adsorption of these inhibitors on mild steel surface obeys Langmuir isotherm. Quantum chemical parameters are calculated using the Density Functional Theory method (DFT) and Monte Carlo simulations. Correlation between theoretical and experimental results is discussed.

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