Different Kinds Of Atoms Research Articles

Ab initio simulation of the dynamic shock response of single crystal and lightweight multicomponent alloy

The dynamic response of shock wave impact on single crystal aluminium and lightweight multicomponent alloy Al-Cu-Li-Mg is simulated by using the combination of Ab initio Molecular Dynamics (AIMD) and Multi-Scale Shock Technique (MSST), with the analysis carried out at the atomic/electronic levels. The simulation is verified by comparing the particle velocity of single crystal obtained in this work with the data in literature. The shock compression process not only involves the migration of atoms, but also is related to electronic transition. Two stages could be found in the shock compression process: oscillatory compression of the crystal cell and oscillatory migration of the atoms. The crystal structure of the multicomponent alloy could be disordered even at low shock speed, due to the difference in the ability to migrate between different kinds of atoms. As the sample is shock-compressed, the contribution proportion of crystal orbitals shows a sharp decrease for D orbital, while it increases significantly for S orbital and P orbital. The electron structure shows a quicker response to the shock wave compression process than the crystal structure. The orbital contribution from P orbital of the crystal is mainly due to the P orbital of Al atoms, while the orbital contribution from D orbital of the crystal is mainly due to the D orbital of Cu atoms. Total Density of States (TDOS) is mainly contributed by the Projected Density of State (PDOS) of Cu atoms in the occupied state of energy levels, while it is close to the PDOS of Al atoms in the non-occupied state of energy levels.

Representation and Reasoning in Vedānta

Abstract This paper considers the matter of representation in Vedānta by examining key claims in the Ṛgveda and the Upaniṣads, which are some of its principal texts. Specifically, we consider the logic behind the paradoxical verses on creation and the conception of consciousness as the ground on which the physical universe exists. This also is the template that explains the logical structure underlying the principal affirmations of the Upaniṣads. The five elements and consciousness are taken to pervade each other, which explains how gross matter is taken to consist of all the four different kinds of atoms that get manifested in different states of the substance. The verses on creation are an example of the use of catuṣkoṭi in Indian philosophy prior to the use of it by Nāgārjuna in the Madhyamaka tradition. It also contrasts central ideas of Vedānta with the corresponding contemporary scientific ideas on consciousness.

Algorithms and programs for the shell decomposition of oscillating functions in space

Real-space refinement of atomic models in macromolecular crystallography and cryo-electron microscopy fits a model to a map obtained with experimental data. To do so, the atomic model is converted into a map of limited resolution and then this map is compared quantitatively with the experimental one. For an appropriate comparison, the atomic contributions comprising the model map should reflect the resolution of the experimental map and the atomic displacement parameter (ADP) values. Such contributions are spherically symmetric oscillating functions, different for chemically different kinds of atoms, different ADPs and different resolution values, and their derivatives with respect to atomic parameters rule the model refinement. For given parameter values, every contribution may be calculated numerically using two Fourier transforms, which is highly time consuming and makes calculation of the respective derivatives problematic. Alternatively, for an atom of each required type its contribution can be expressed in an analytical form as a sum of specially designed terms. Each term is different from zero essentially inside a spherical shell, and changing the ADP value does not change its form but rather changes the value of one of its arguments. In general, these terms become a convenient tool for the decomposition of oscillating spherically symmetric functions. This work describes the algorithms and respective software, named dec3D, to carry out such a shell decomposition for density contributions of different kinds of atoms and ions.

Synthesis and Identification of New Heterocyclic Compounds from Isatin by Schiff Base Reaction

Heterocyclic compounds possess a cyclic structure with two or more different kinds of atoms in the ring. The history of heterocyclic chemistry began in the 1800s, in step with the development of organic chemistry. Since rings can be of any size, from three-membered upwards, and since the heteroatoms can be drawn in almost any combination from a large number of the elements (though nitrogen, oxygen, and sulfur are still by far the most common), the number of possible heterocyclic systems is almost limitless. An enormous number of heterocyclic compounds are known and this number continues to increase very rapidly. This work is divided into two different parts: First part: Synthesis of imines by Schiff base reaction, this part involves synthesis three of imines by treatment isatin with a variety of cyclo primary amines. Second part: [3 + 2] Cycloaddition reaction, this part includes reacting each product of the first part with two types of amino acids. All steps of reactions followed by TLC– papers. All synthesized compounds were confirmed through the use of different spectroscopic techniques (IR and NMR), melting points.

Study on Environmental Characteristics Of Jupiter System And Spacecraft Protection Design

The Jovian system exploration is one of the important fields of deep space exploration in China in the future. The environments in Jupiter’s system are very complex. The exploration of the environments in Jupiter’s system is an important scientific goal. Besides that, the impact of space environment on the spacecraft is also a key factor that restricting the mission design. In this study, the characteristics and research status of gravity field, magnetic field, atmosphere/exosphere, electromagnetic radiation, high-energy particle radiation, plasma, and meteoroids in Jupiter’s system are analyzed. The gravity field model is an important basis for the design of the orbit and propulsion subsystem and the redundant model needs to be built. Jupiter strong magnetic field constraints the design of sensitive electromagnetic equipment in control subsystem. The main sources of electromagnetic radiation in Jupiter’s orbit include solar radiation, Jupiter/Satellite reflection radiation, and Jupiter infrared radiation. The exospheres of Jupiter’s moons are thin but include different kinds of atoms. The flux of plasma and high-energy particles in Jupiter’s orbit is much higher than that in Earth’s orbit. They can produce a variety of radiation effects. Among these the focus of protection is total dose and internal charging. The sources of meteoroids include interplanetary and Jupiter system. The risk of surface degradation or breakdown caused by collision between meteoroids and spacecraft should be avoided.

Disentangling Self-Atomic Motions in Polyisobutylene by Molecular Dynamics Simulations.

We present fully atomistic molecular dynamics simulations on polyisobutylene (PIB) in a wide temperature range above the glass transition. The cell is validated by direct comparison of magnitudes computed from the simulation and measured by neutron scattering on protonated samples reported in previous works. Once the reliability of the simulation is assured, we exploit the information in the atomic trajectories to characterize the dynamics of the different kinds of atoms in PIB. All of them, including main-chain carbons, show a crossover from Gaussian to non-Gaussian behavior in the intermediate scattering function that can be described in terms of the anomalous jump diffusion model. The full characterization of the methyl-group hydrogen motions requires accounting for rotational motions. We show that the usually assumed statistically independence of rotational and segmental motions fails in this case. We apply the rotational rate distribution model to correlation functions calculated for the relative positions of methyl-group hydrogens with respect to the carbon atom at which they are linked. The contributions to the vibrational density of states are also discussed. We conclude that methyl-group rotations are coupled with the main-chain dynamics. Finally, we revise in the light of the simulations the hypothesis and conclusions made in previously reported neutron scattering investigations on protonated samples trying to address the origin of the dielectric -process.

Inversion of the Contribution of an Isotope of Small Relative Concentration to Total Absorption Coefficient of a Mixture of Neon Isotopes Associated with the 3s2–2p4 Transition

Absorption of probe laser radiation by a mixture of even isotopes of neon in a gas discharge plasma is investigated by the method of magnetic scanning of 3s2–2p4 transition. The contours of absorption lines of isotopes are resolved by means of numerical modeling. It is discovered that, upon decrease in relative concentration of one of the isotopes, its contribution to absorption is replaced by gain. The effect is found to be caused by radiative transfer of excitation energy between atoms of different kinds in the absence of a difference in level energies (the process known as optical pumping). The effect of this mechanism turned out to be substantial for the upper level transitions from which to the ground state are allowed while being absent for the lower level of the transition from which such transitions are forbidden although other decay channels are available.

Инверсия вклада изотопа малой относительной концентрации в суммарный коэффициент поглощения смеси изотопов неона на переходе 3s-=SUB=-2-=/SUB=--2p-=SUB=-4-=/SUB=-

AbstractAbsorption of probe laser radiation by a mixture of even isotopes of neon in a gas discharge plasma is investigated by the method of magnetic scanning of 3 s _2–2 p _4 transition. The contours of absorption lines of isotopes are resolved by means of numerical modeling. It is discovered that, upon decrease in relative concentration of one of the isotopes, its contribution to absorption is replaced by gain. The effect is found to be caused by radiative transfer of excitation energy between atoms of different kinds in the absence of a difference in level energies (the process known as optical pumping). The effect of this mechanism turned out to be substantial for the upper level transitions from which to the ground state are allowed while being absent for the lower level of the transition from which such transitions are forbidden although other decay channels are available.

First-principles study on doping of tetragonal ZnSe monolayers

Doping is a very important and effective method to be used to modulate the properties of two-dimensional (2D) materials. In this work, the electronic and magnetic properties of ultrathin tetragonal ZnSe monolayer doped by twenty different kinds of atoms neighboring Zn/Se were systemically investigated using first-principles calculations. Substitution at the Zn/Se sites was found to be easy if the monolayer was grown under Zn-/Se-poor conditions. Among non-metal dopants, only F atom is thermodynamically favored to replace Se atom, while a number of metal atoms (i.e. Ca, Sc, Ti, and Mn) are able to substitute Zn atom. It is suggested by theoretical calculations that pristine ZnSe monolayer inclines as an n-type semiconductor by certain doping. Our results open a new avenue for the modulation of the novel tetragonal ZnSe monolayer for a wealth of potential optoelectronic applications.

Influential Electronic and Magnetic Properties of the Gallium Sulfide Monolayer by Substitutional Doping

The structural, electronic, and magnetic properties of the GaS monolayer doped by 12 different kinds of atoms were investigated systemically using first-principles calculations. N is found to be the most promising candidate for p-type doping among dopants at the S site, including nonmetal atoms H, B, C, N, O, and F and transition metal atoms V, Cr, Mn, Fe, Co, and Ni. Transition metal atoms appear to be hardly incorporated in the GaS monolayer under either S- or Ga-rich conditions. While the net magnetic moments of doped GaS by nonmetal atoms are either 0 or 1 μB, the value of transition metal dopants decreases from 5 to 0 μB by adding the number of valence electrons from V to Ni. In the case of transition metal dopants at the Ga site, the majority spin states of Cr and Co are located closest to the conduction band minimum and valence band maximum, respectively. Magnetic ground states exist in all of the monolayers doped by these impurities. Indirect band gap of the pristine GaS monolayer is regulated to ...

Portevin–Le Chatelier Effect in Nimonic 263 Superalloy

The Portevin–Le Chatelier (PLC) effect in the Nimonic 263 superalloy was investigated by tensile test at a wide temperature ranges from 293 to 1033 K and strain rates between 0.1 and 6.25 × 10−6 s−1. Simple binary alloys Ni-0.4C, Ni-24Cr and Ni-5(8)Mo were also tested in order to identify which elements were responsible for the PLC effect in the Nimonic 263 alloy. The results demonstrated that for Nimonic 263 alloy, PLC effect occurred at certain temperatures and low strain rates. Normal PLC effect exhibiting type-A and -(A + B) serrations was attributed to the enhanced solute diffusion with increasing temperature, while inverse PLC effect with type-C serration was caused by unlocking process. The activation energy for the normal PLC effect was calculated to be 68 kJ/mol, and diffusion of substitutional solutes such as Cr and Mo was identified to be responsible for the PLC effect. In comparison with the PLC effect in simple binary alloys, solute atmospheres formed by different kinds of atoms in Nimonic 263 alloy work more effectively, increasing locking strength and corresponding mean stress drop magnitude.

Work Functions of Pristine and Heteroatom-Doped Graphenes under Different External Electric Fields: Anab InitioDFT Study

Low contact barrier electrodes and various field-emitting devices require a tunable work function, and graphene is a dream material for these applications. In this work, the theoretical investigations on the variation of the work function for monolayer graphene doped with different kinds of atoms from groups IIA–VIA of the Periodic Table are reported. The geometry, density of states, dipole moment, and work function of each heteroatom-doped graphene are calculated using ab initio density functional theory with a dispersion correction. The obtained formation energy of the heteroatom-doped graphenes is in the order: N < B < P < O < S < Si < As < Se < Ge < Al < Ga. The work functions without an electric field abide by a periodic law in terms of doping atoms except for O-doped graphene. The calculated results demonstrate that the work functions of all heteroatom-doped graphenes are a linear function of the applied external electric field intensity, and the slopes of the lines deviate from the ideal value to a different extent, which is mainly dependent on the polarization of the heteroatom–carbon bonds and the production of the induced dipole moments of the doped graphenes. The present calculated results make it known that the graphene work function can be tinkered up from 0.5 to 8.5 eV by using different kinds of doping atoms of group IIIA–VIA elements and applying an electric field with various intensities. Such a wide range of adjustable work function makes graphene a very promising material for contact electrodes and field-emitting devices.

Symmetry groups of single-wall nanotubes

This work investigates the symmetry properties of single-wall carbon nanotubes and their structural analogs, which are nanotubes consisting of different kinds of atoms. The symmetry group of a nanotube is studied by looking at symmetries and color fixing symmetries associated with a coloring of the tiling by hexagons in the Euclidean plane which, when rolled, gives rise to a geometric model of the nanotube. The approach is also applied to nanotubes with non-hexagonal symmetry arising from other isogonal tilings of the plane.

Two-photon–two-atom excitation by correlated light states

We study the efficiency of different two-photon states of light to induce the simultaneous excitation of two atoms of different kinds when the sum of the energies of the two photons matches the sum of the energies of the two atomic transitions, while no photons are resonant with each individual transition. We find that entangled two-photon states produced by an atomic cascade are indeed capable of enhancing by a large factor the simultaneous excitation probability as compared to uncorrelated photons, as predicted some years ago by Muthukrishnan et al., but that several unentangled, separable, correlated states, produced either by an atomic cascade or parametric down-conversion, or even appropriate combinations of coherent states, have comparable efficiencies. We show that the key ingredient for the increase of simultaneous excitation probability is the presence of strong frequency anticorrelation and neither time correlation nor time-frequency entanglement.

A computer study of the Raman spectra of the (GaN)129, (SiO2)86, and (GaN)54(SiO2)50 nanoparticles

The Raman spectra of the (GaN)129, (SiO2)86, and (GaN)54(SiO2)50 nanoparticles were calculated using the molecular dynamics method. The spectrum of (SiO2)86 had three broad bands only, whereas the Raman spectrum of (GaN)129 contained a large number of overlapping bands. The form of the Raman spectrum of (GaN)54(SiO2)50 was determined by the arrangement of the GaN and SiO2 components in it. The nanoparticle with a GaN nucleus had a continuous fairly smooth spectrum over the frequency range 0 ≤ ω ≤ 600 cm−1, whereas the spectrum of the nanoparticle with a SiO2 nucleus contained well-defined bands caused by vibrations of groups of atoms of different kinds and atoms of the same kind.

Structural features of Co-Si, Co-Ge, and Co-Sn binary melts

A comparative analysis of the local structures of binary Co— IVA Group element (Si, Ge, Sn) melts is performed using partial structural characteristics, which were calculated by three-dimensional mod els reconstructed from experimental structure factor curves by reverse Monte Carlo method. These melts are characterized by a common feature that consists in the existence of a marked interaction between atoms of different kinds, which are located at distances close to those in the corresponding intermetallics. Zigzag chains formed by covalently bound silicon and germanium atoms are found to exist in Co— Si and Co— Ge melts. This is due to the thermal dissociation of the intermetallics during melting and partial retention of the covalent bond between germanium atoms in higher germanides. In passing from Co— Si to Co— Ge and Co— Sn melts, a marked increase in the interaction between cobalt atoms takes place along with a decrease in the interaction between second-component atoms; in particular, this is especially typical of Co— Sn melts.

Magnetic behavior of cosputtered Fe-Zr amorphous thin films exhibiting perpendicular magnetic anisotropy

Excellent mechanical properties of amorphous or glassy metals along with the capability to fabricate sub-50-nm patterns promise their application as a futuristic material for production of various nano- or microelectromechanical systems. In addition to their applications, these materials pose a lot of challenges in understanding their fundamental properties because of their random structure and involvement of three or more different kinds of atoms. The amorphous Fe-Zr system which is reported to exhibit superconductivity, ferromagnetism, spin glass, and antiferromagnetism is an ideal system to understand. The controversial magnetic properties of this system are still a subject of debate. In the present paper we revisited Fe-Zr system and studied their detailed magnetic properties in the temperature range of 5--330 K. ${\text{Fe}}_{x}{\text{Zr}}_{100\ensuremath{-}x}$ ($x=63$, 68, 76, 86, 92, and $93\text{ }\text{at}\text{.}\text{ }%$) thin films were deposited on silicon (100) substrate by a cosputtering technique. The Curie temperature $({T}_{c})$ is shown to increase almost linearly with an increase in Fe concentration, but it decreases rapidly for the Fe-rich films. The films with $x$ up to $\ensuremath{\sim}86\text{ }\text{at}.\text{ }%$ have a strange shape of the hysteresis loop and are shown to exhibit perpendicular magnetic anisotropy with a stripe domain structure. Hysteresis loop shapes are correlated with the magnetic structure of the films, and provide an easy understanding of magnetic properties. It has been shown that the Fe-rich films are composed of antiferromagnetic Fe clusters which are embedded in the ferromagnetic amorphous FeZr.

Monte Carlo calculation of electron Rutherford backscattering spectra and high-energy reflection electron energy loss spectra

The electron Rutherford backscattering spectra and high-energy reflection electron energy loss spectra have been calculated by a Monte Carlo method for bulk solids and overlayer/substrate systems. The simulation model is mainly based on the use of Mott cross section for elastic scattering and the use of Penn’s dielectric functional approach to the electron inelastic scattering inside the solid. Moreover, it has further considered the recoil energy loss of energetic electrons and the thermal vibration of atoms with an isotropic distribution of the velocity direction. The calculated energy loss spectra for Al/Pt and Al/Mo agree with the experimental spectra quite well. The signals owing to different kinds of atoms can be separated by taking the scatter for the maximum-scattering angle event along an electron trajectory as the Rutherford backscattering atom, enabling a theoretical estimation of the peak intensity ratio. Furthermore, the simulation has also indicated that the multiple scattering is the dominant process to the quasi-elastic and energy loss of the electrons and is responsible mainly to the difference on the peak intensity between the linear model and experiment.

Ultrahigh-resolution study of protein atomic displacement parameters at cryotemperatures obtained with a helium cryostat

Two X-ray data sets for a complex of human aldose reductase (h-AR) with the inhibitor IDD 594 and the cofactor NADP(+) were collected from two different parts of the same crystal to a resolution of 0.81 A at 15 and 60 K using cold helium gas as cryogen. The contribution of temperature to the atomic B values was estimated by comparison of the independently refined models. It was found that although being slightly different for different kinds of atoms, the differences (deltaB) in the isotropic equivalents B of atomic displacement parameters (ADPs) were approximately constant (about 1.7 A(2)) for well ordered atoms as the temperature was increased from 15 to 60 K. The mean value of this difference varied according to the number of non-H atoms covalently bound to the parent atom. Atoms having a B value of higher than 8 A(2) at 15 K showed much larger deviations of deltaB from the average value, which might reflect partial occupancy of atomic sites. An analysis of the anisotropy of ADPs for individual atoms revealed an increase in the isotropy of ADPs with the increase of the temperature from 15 to 60 K. In a separate experiment, a 0.93 A resolution data set was collected from a different crystal of the same complex at 100 K using cold nitrogen as a cryogen. The effects of various errors on the atomic B values were estimated by comparison of the refined models and the temperature-dependent component was inferred. It was found that both decreasing the data redundancy and increasing the resolution cutoff led to an approximately constant increase in atomic B values for well ordered atoms.

Hartree–Fock Energy Partitioning in Terms of Hirshfeld Atoms

A Hirshfeld decomposition scheme of the Hartree-Fock total molecular energy into atomic energies is presented. The calculations are performed by direct numerical integration and the results are compared for a set of 28 molecules containing different kinds of atoms. The calculated atomic energies show a strong dependency on changes of atomic electron population and hybridization. Linear correlations are found between the energy and the population for H, these being related to the electronegativity of this atom and to the external potential created by the remaining atoms. The proposed energy partitioning scheme appears to be useful for studies such as proton acidity, the anomeric effect and group transferability, and allows atomic virial ratios to be obtained. Finally, the atomic potential energies are found to mimic trends based on exact expressions as well as trends displayed by molecular quantities, thus lending credibility to the partitioning scheme used.