scholarly journals STUDY OF POTASSIUM INTERCALATION IN TO THE GRAPHENE/MoS STRUCTURE

2021 ◽  
pp. 639-645
Author(s):  
Илья Васильевич Чепкасов
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Formation Energy ◽  
Potassium Atom ◽  
Structure Calculation ◽  
Mos Structure ◽  
Layer Graphene ◽  
Low Concentrations ◽  
The Difference ◽  
Covalent Nature

Используя современные расчеты из первых принципов, в данной работе мы систематически изучали интеркаляцию атомов калия в гибридную двухслойную структуру графене/ MoS. В ходе исследования были определенны концентрации атомов калия при которых энергия формирования является отрицательной. Так в частности при концентрации атомов калия, по отношению к атомам молибдена, не более x = 0,43 формирование слоя атомов калия между слоями графен/ MoS является энергетически выгодным. Начиная с концентрации атомов калия x > 0,75 наблюдается увеличение расстояние между слоями графен и MoS, что в дальнейшем приводит к разрушению структуры. Расчет зарядов показал, что атом калия при небольших концентрациях отдает примерно 0,8 - 0,85 электрона, 0,35 из которых перетекает на атомы углерода, а 0,4 - 0,5 перетекает на дисульфид молибдена. Расчёт разность электронных плотностей показал, что связь между слоями графена, дисульфид молибдена и калия имеет ковалентный характер. Using modern ab-initio calculations, in this work, we systematically studied the intercalation of potassium atoms into a hybrid two-layer graphene/MoS structure. In the course of the study, concentrations of potassium atoms were determined at which the formation energy is negative. So, in particular, when the concentration of potassium atoms (in relation to molybdenum atoms) is not more than x = 0,43, formation of a layer of potassium atoms between the graphene/ MoS layers is energetically favorable. Beginning with the concentration of potassium atoms x > 0,75 , an increase in the distance between the graphene and MoS layers is observed, which further leads to destruction of the structure. Calculation of charges showed that a potassium atom at low concentrations gives up about 0,8 - 0,85 electrons, 0,35 of which flow on carbon atoms, and 0,4 - 0,5 to molybdenum disulfide. Calculation of the difference in electron densities showed that the bond between the layers of graphene, molybdenum and potassium disulfide has a covalent nature.

scholarly journals Three-nucleon forces

2014 ◽  
Vol 23 (09) ◽  
pp. 1430015 ◽  
Author(s):  
Peter U. Sauer
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Body Problem ◽  
Many Body ◽  
Nuclear Systems ◽  
The Difference

In this paper, the role of three-nucleon forces in ab initio calculations of nuclear systems is investigated. The difference between genuine and induced many-nucleon forces is emphasized. Induced forces arise in the process of solving the nuclear many-body problem as technical intermediaries toward calculationally converged results. Genuine forces make up the Hamiltonian. They represent the chosen underlying dynamics. The hierarchy of contributions arising from genuine two-, three- and many-nucleon forces is discussed. Signals for the need of the inclusion of genuine three-nucleon forces are studied in nuclear systems, technically best under control, especially in three-nucleon and four-nucleon systems. Genuine three-nucleon forces are important for details in the description of some observables. Their contributions to observables are small on the scale set by two-nucleon forces.

Nuclear magnetic shielding tensors for the carbon, nitrogen, and selenium nuclei of selenocyanates - a combined experimental and theoretical approach

2000 ◽  
Vol 78 (5) ◽  
pp. 614-625 ◽  
Author(s):  
Guy M Bernard ◽  
Klaus Eichele ◽  
Gang Wu ◽  
Christopher W Kirby ◽  
Roderick E Wasylishen
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Magic Angle Spinning ◽  
Magic Angle ◽  
Axially Symmetric ◽  
Paramagnetic Contribution ◽  
Shielding Tensors ◽  
The Difference ◽  
Shielding Tensor ◽  
Angle Spinning

The principal components of the carbon, nitrogen, and selenium chemical shift (CS) tensors for several solid selenocyanate salts have been determined by NMR measurements on stationary or slow magic-angle-spinning powder samples. Within experimental error, all three CS tensors are axially symmetric, consistent with the expected linear geometry of these anions. The spans (Ω) of the carbon and selenium CS tensors for the selenocyanate anion (SeCN-) are approximately 300 and 800 ppm, respectively, much less than the corresponding values for carbon diselenide (CSe2). This difference is a consequence of the difference in the CS tensor components perpendicular to the C infiniti symmetry axes in these systems. Ab initio calculations show that the orbital symmetries of these compounds are a significant factor in the shielding. For CSe2, efficient mixing of the σ and π orbitals results in a large paramagnetic contribution to the total shielding of the chemical shielding tensor components perpendicular to the molecular axis. Such mixing is less efficient for the SeCN-, resulting in a smaller paramagnetic contribution and hence in greater shielding in directions perpendicular to the molecular axis.Key words: selenocyanates, solid-state NMR, carbon shielding tensors, nitrogen shielding tensors, selenium shielding tensors, ab initio calculations.

scholarly journals Nitrogen Dissolution in Liquid Ga and Fe: Comprehensive Ab Initio Analysis, Relevance for Crystallization of GaN

Materials ◽  
2021 ◽  
Vol 14 (5) ◽  
pp. 1306
Author(s):  
Jacek Piechota ◽  
Stanislaw Krukowski ◽  
Petro Sadovyi ◽  
Bohdan Sadovyi ◽  
Sylwester Porowski ◽  
...  
Keyword(s):  
Experimental Data ◽  
Molecular Dynamics ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Chemical Potential ◽  
Nitrogen Solubility ◽  
Molecular Nitrogen ◽  
Ideal Gas ◽  
The Difference ◽  
Good Agreement

The dissolution of molecular nitrogen in Ga and Fe was investigated by ab initio calculations and some complementary experiments. It was found that the N bonding inside these solvents is fundamentally different. For Ga, it is between Ga4s and Ga4p and N2p states whereas for Fe this is by N2p to Fe4s, Fe4p and Fe3d states. Accordingly, the energy of dissolution of N2 for arbitrarily chosen starting atomic configurations was 0.535 eV/mol and −0.299 eV/mol for Ga and Fe, respectively. For configurations optimized with molecular dynamics, the difference between the corresponding energy values, 1.107 eV/mol and 0.003 eV/mol, was similarly large. Full thermodynamic analysis of chemical potential was made employing entropy-derived terms in a Debye picture. The entropy-dependent terms were obtained via a normal conditions path to avoid singularity of ideal gas entropy at zero K. Nitrogen solubility as a function of temperature and N2 pressure was evaluated, being much higher for Fe than for Ga. For T=1800 K and p=104 bar, the N concentration in Ga was 3×10−3 at. fr. whereas for Fe, it was 9×10−2 at. fr. in very good agreement with experimental data. It indicates that liquid Fe could be a prospective solvent for GaN crystallization from metallic solutions.

Role of Thermal Expansion and Redistribution of Components on the Temperature Dependence of the Lattice Misfit in γ/γ' Superalloys

2006 ◽  
Vol 980 ◽  
Author(s):  
Oleg Kontsevoi ◽  
Yuri N. Gornostyrev ◽  
Arthur J. Freeman
Keyword(s):  
Thermal Expansion ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Temperature Dependence ◽  
Temperature Region ◽  
Lattice Misfit ◽  
Slight Variation ◽  
Relative Role ◽  
The Difference

AbstractThe relative role of thermal expansion and redistribution of alloy components in the temperature dependence of the lattice misfit in γ/γ' alloys is investigated on the basis of ab initio calculations. We show that in a wide temperature region up to approximately 0.6·Tmelt, the lattice misfit is determined by the difference in thermal expansion of γ and γ' phases and shows only a slight variation. For higher temperatures the redistribution of the major alloy components between the phases becomes a leading contribution to the lattice misfit.

Hydrogen, Acceptors, and H-Acceptor Complexes in GaN

1995 ◽  
Vol 395 ◽  
Author(s):  
Andrea Bosin ◽  
Vincenzo Fiorentini ◽  
David Vanderbilt
Keyword(s):  
Complex Formation ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Atomic Hydrogen ◽  
Formation Energy ◽  
Impurity Level ◽  
Mbe Growth ◽  
Hydrogen Incorporation ◽  
Shallow Impurity ◽  
Mg Doped

ABSTRACTWe present ab-initio calculations on energetics and geometries of atomic hydrogen, of several candidate acceptors, and of H-acceptor complexes in wurtzite GaN For the H-Mg complex in Mg-doped GaN, we calculate the vibrational frequencies of H. Hydrogen is found to be a negative-U center. H-acceptor complex formation is always exothermic. Substitutional Be has a low formation energy and a shallow impurity level, which makes it a good candidate for p-doping in MBE growth. CN appears not to be shallow. Atomic hydrogen incorporation in undoped GaN is disfavored in an H2 atmosphere; it becomes favorable in p and n-type conditions in atomic H environments.

Ab initio and Semiempirical Studies on H3C-B=O and H-B=O. Their Structure and Vibrational Spectra

1987 ◽  
Vol 42 (9) ◽  
pp. 1027-1036
Author(s):  
Gerhard Raabe ◽  
Wolfgang Schleker ◽  
Wolfgang Straßburger ◽  
Eberhard Heyne ◽  
Jörg Fleischhauer ◽  
...  
Keyword(s):  
Electronic Structure ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Vibrational Spectra ◽  
Basis Sets ◽  
Vertical Ionization Potential ◽  
Methyl Substitution ◽  
Isotopic Shifts ◽  
The Difference ◽  
Semiempirical Mndo

The electronic structure of H3C -BO and H - BO is elucidated employing one determinant ab initio calculations with STO-3G and 4-31G basis sets and the semiempirical MNDO theory. The vibrational spectra of both molecules including various isotopic shifts have been calculated at the 4-31G level. The influence of methyl substitution on the vibrational frequencies, BO stretching force constant, Mulliken charges, and vertical ionization potential is examined and compared with that in the pairs H-CN/H3C-CN and H-NC/H3C-NC , isoelectronic with H-BO/H3C-BO.As judged from a comparison of the force constants for stretching the XY bonds in the H3C -XY and H-XY molecules, the XY bond is “softened” upon methyl substitution. This effect is found to decrease in the order H3C-BO>H3C-CN>H3C-NC.For XY=BO the difference between the first ionization potentials of H-XY and H3C-XY is found to be somewhat smaller than for XY = CN but slightly higher than for the isonitril compounds (XY = NC).

Structure of low concentrations of vanadium on TiO2 determined by XANES and ab initio calculations

2002 ◽  
pp. 2402-2403 ◽  
Author(s):  
Yasuo Izumi ◽  
Fumitaka Kiyotaki ◽  
Hideaki Yoshitake ◽  
Ken-ichi Aika ◽  
Tae Sugihara ◽  
...  
Keyword(s):  
Ab Initio Calculations ◽  
Ab Initio ◽  
Low Concentrations

Millimetre-wave and infrared spectroscopy of Br13 CN: anharmonic force field of cyanogen bromide from spectroscopic data and ab initio calculations

1997 ◽  
Vol 90 (3) ◽  
pp. 495-497
Author(s):  
CLAUDIO ESPOSTI ◽  
FILIPPO TAMASSIA ◽  
CRISTINA PUZZARINI ◽  
RICCARDO TARRONI ◽  
ZDENEK ZELINGER
Keyword(s):  
Infrared Spectroscopy ◽  
Force Field ◽  
Ab Initio Calculations ◽  
Ab Initio ◽  
Spectroscopic Data ◽  
Cyanogen Bromide ◽  
Millimetre Wave ◽  
Anharmonic Force
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