scholarly journals Are Metallacyclopentadienes Always Non-Aromatic?

Chemistry ◽  
2021 ◽  
Vol 3 (4) ◽  
pp. 1302-1313
Author(s):  
Ricardo Casiano-González ◽  
José Enrique Barquera-Lozada
Keyword(s):  
Energy Density ◽  
Current Density ◽  
Stabilization Energy ◽  
Electron Delocalization ◽  
Great Stability ◽  
Magnetic Current ◽  
Theoretical Account ◽  
Delocalization Index ◽  
Density Delocalization

Even though metallacyclopentadienes (MCPs) are among the most common metallacycles, their electron delocalization (aromaticity) has received far less attention than other metallacycles, such as metallabenzenes. We systematically studied the aromaticity of MCPs with energetic (isomerization stabilization energy), density (delocalization index) and magnetic (current density) aromaticity indices. The indices agree that metallacyclopentadienes are, in general, weakly aromatic at most. The 18e− complexes showed the expected weak aromaticity, and only the d8 molecules are somewhat anti-aromatic. However, the theoretical account of the aromaticity of the 16e− MCPs is more convoluted. We find that the aromatic criteria for a 16e−d4 ruthenacyclopentadiene disagree. The lack of agreement shows that significant electron delocalization is not always related to great stability or to strong diatropic currents.

scholarly journals A study of the nature of the field theories of the electron and positron and of the meson

1946 ◽  
Vol 185 (1000) ◽  
pp. 14-34 ◽  
Keyword(s):  
Current Density ◽  
Magnetic Moment ◽  
Poynting Vector ◽  
Field Theories ◽  
Meson Field ◽  
Theory Of Relativity ◽  
Magnetic Current ◽  
Additional Degree ◽  
Additional Dimension ◽  
A Current

The field theories of the electron and positron and also of the meson are developed by means of a close analogy with the photon. The analogy consists in the representation of the tracks of these particles by means of null-geodesics. The choice of notation is guided by the attempt to arrive at a theory in which the lengths (h/m 0 c) and (e 2 /m 0 c 2 ) occur naturally without reference to the structure of the particles, and in which the concept of quantization of electric charge is included. It is found that these objects can be attained by assuming that an additional degree of freedom is necessary for the description of the particles. If this is regarded as an additional dimension, it is found that an exact analogy can be made with the field theories familiar in the theory of relativity. An important feature is the union, in a single tensor, of energy, momentum and current density. A certain arbitrariness, not unlike that associated with the Poynting vector, is revealed, and it is shown that if this is removed by making a definite choice of the magnitude of the magnetic moment of the electron and positron, the spin angular momefttum is ^hereby fixed at the value 1/2h. In the development of the meson field the analogy shows* that the nuclear sources of the field act as if contributing a current density analogous to a magnetic current density in the electromagnetic case. The use of the additional degreb of freedom in the sinusoidal form indicates that the ratio of the constants g 1 and g 2 introduced into field theories as measures of the strengths of the sources is determined by the mass of the particle emitted in the neutron-proton transition.

Electron delocalization index based on bond order orbitals

2014 ◽  
Vol 593 ◽  
pp. 154-159 ◽  
Author(s):  
Dariusz W. Szczepanik ◽  
Emil Żak ◽  
Karol Dyduch ◽  
Janusz Mrozek
Keyword(s):  
Bond Order ◽  
Electron Delocalization ◽  
Delocalization Index

Kraftfreie Magnetfelder II

1957 ◽  
Vol 12 (10) ◽  
pp. 855-859 ◽  
Author(s):  
A. Schlüter
Keyword(s):  
Differential Equation ◽  
Angular Momentum ◽  
Energy Density ◽  
Magnetic Fields ◽  
General Solution ◽  
Current Density ◽  
Cylindrical Symmetry ◽  
Axis Of Symmetry ◽  
Free Fields ◽  
Electric Flux

Die allgemeine Lösung der Differentialgleichung der kraftfreien Magnetfelder wird für den zylindersymmetrischen Fall angegeben. Die Energiedichte des Magnetfeldes kann als Funktion des Abstandes von der Symmetrieachse vorgegeben werden, sie muß nur zwei Ungleichungen befriedigen. Die Komponenten des magnetischen Feldvektors und der elektrischen Stromdichte folgen dann durch Differentiation. Durch Konstruktion eines Beispiels wird gezeigt, daß ein solches Feld Impuls und Drehimpuls in Richtung der Achse transportieren kann in einem Ausmaß, das durch den Gesamtstrom und den gesamten magnetischen Fluß nicht bestimmt ist.The general solution of the differential equation of force-free magnetic fields is given in the case of cylindrical symmetry. The energy density has to fulfil two inequalities; apart from this, it can be freely chosen as function of the distance from the axis of symmetry. The components of the field as well as the electric current density follow from it purely by differentiation. By explicitly constructing a three-parameter family of such force-free fields it is shown that the amount of momentum and of angular momentum transported by the field in the direction of the axis is not determined by the total magnetic and electric flux of the field.

Analyses and Determination of Current Density and Energy Density in Electric Melting Glass Furnace

2011 ◽  
Vol 287-290 ◽  
pp. 2945-2951
Author(s):  
Wei Ning ◽  
Li Da Luo ◽  
Xing Yang Xu ◽  
Qing Wei Wang ◽  
Jian Chen
Keyword(s):  
Energy Density ◽  
Glass Furnace ◽  
Current Density ◽  
Empirical Equation ◽  
Melting Rate ◽  
Optimum Operating ◽  
Electric Melting ◽  
Optimum Operating Condition ◽  
Melting Glass

Current density and energy density is one of the most important parameters for designing the electric melting glass furnace. This paper analyzed the relation between current density and energy density based upon the generated representation, mathematical simulation and empirical equation, defined the bearing scope of current density for several kinds of electrodes, discussed the tendency of the change of current density and volume melting rate on different kinds of glasses, provided the theoretical basis to design electric melting glass furnace and established proper thermotechnical regime, so as to ensure the optimum operating condition in electric melting glass furnace.

scholarly journals Electrochemical Performance of Lithium-Ion Capacitors Using Pre-Lithiated Multiwalled Carbon Nanotubes as Anode

NANO ◽  
2017 ◽  
Vol 12 (04) ◽  
pp. 1750051 ◽  
Author(s):  
Manyuan Cai ◽  
Xiaogang Sun ◽  
Yanyan Nie ◽  
Wei Chen ◽  
Zhiwen Qiu ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Carbon Nanotubes ◽  
Carbon Nanotube ◽  
Energy Density ◽  
Electrochemical Performance ◽  
Multiwalled Carbon Nanotubes ◽  
Current Density ◽  
Lithium Ion ◽  
Multiwalled Carbon ◽  
Charge Discharge

Pre-lithiated multiwalled carbon nanotube anode was prepared by internal short circuit approach(ISC) for 5[Formula: see text]min, 30[Formula: see text]min, 60[Formula: see text]min and 120[Formula: see text]min respectively. Lithium ion capacitors (LICs) were assembled by using pre-lithiated multiwalled carbon nanotubes as anodes and activated carbon (AC) as cathodes. The structure of multiwalled carbon nanotubes and electrodes were investigated by scanning electron microscopy (SEM) and transmission electron microscopy (TEM). The electrochemical performance of pre-lithiated multiwalled carbon nanotube electrodes and pristine carbon nanotube electrodes were tested by galvanostatic charge/discharge and electrochemical impedance. The results indicated that pre-lithiation carbon nanotubes greatly improved the charge/discharge performance of LICs. The energy density was four times than conventional electric double-layer capacitors (EDLCs) at the current density of 100[Formula: see text]mA/g. The LICs achieved a specific capacitance of 59.3[Formula: see text]F/g at the current density of 100[Formula: see text]mA/g with 60[Formula: see text]min pre-lithiatiation process. The maximum energy density and power density was 96[Formula: see text]Wh/kg and 4035[Formula: see text]W/kg, respectively. The energy density still remained about 89.0% after 1000 cycles. The LIC showed excellent supercapacitor performance.

scholarly journals Energy density distribution of a modulated electron beam in a source with a plasma cathode based on a low pressure arc

2021 ◽  
Vol 2064 (1) ◽  
pp. 012066
Author(s):  
V I Shin ◽  
P V Moskvin ◽  
M S Vorobyov ◽  
V N Devyatkov ◽  
N N Koval
Keyword(s):  
Electron Beam ◽  
Energy Density ◽  
Density Distribution ◽  
Current Pulse ◽  
Current Density ◽  
Beam Current ◽  
Beam Current Pulse ◽  
Energy Density Distribution ◽  
Electron Beam Generation ◽  
Arc Current

Abstract The article presents the results of studies devoted to the study of the energy density distribution in the amplitude-modulated regime of electron beam generation. It is shown that in the first ≈ 50 μs of the duration of the beam current pulse, its spatial rearrangement occurs, due to the development of the arc discharge current. Thus, the rearrangement of the arc current, which develops from the axis of the system, leads to an axial diving of the emission current density and the beam current density on the target. With the development of the arc current, the energy density on the target on the axis of the system decreases and after ≈ 50 μs takes on a steady-state value, which can change only as a result of a change in the conditions for generating an electron beam or the transition to a modulated regime of electron beam generation. It has been experimentally shown using calorimetric measurements that the shape of the electron beam current pulse with its amplitude modulation with a pulse duration of more than 100 μs has little effect on the distribution of the beam energy density in the target region.

scholarly journals One-Step Hydrothermal Synthesis of a CoTe@rGO Electrode Material for Supercapacitors

2021 ◽  
Author(s):  
Tianrui Wang ◽  
Yupeng Su ◽  
Mi Xiao ◽  
Meilian Zhao ◽  
Tingwu Zhao ◽  
...  
Keyword(s):  
Energy Density ◽  
Specific Capacitance ◽  
Power Density ◽  
Current Density ◽  
Electrode Material ◽  
High Energy ◽  
Cycling Stability ◽  
High Energy Density ◽  
One Step ◽  
Charge Discharge

AbstractCoTe@reduced graphene oxide (CoTe@rGO) electrode materials for supercapacitors were prepared by a one-step hydrothermal method in this paper. Compared with that of pure CoTe, the electrochemical performance of CoTe@rGO was significantly improved. The results showed that the optimal CoTe@rGO electrode material has a remarkably high specific capacitance of 810.6 F/g at a current density of 1 A/g. At 5 A/g, the synthesized material retained 77.2% of its initial capacitance even after 5000 charge/discharge cycles, thereby demonstrating good cycling stability. Moreover, even at a high current density of 20 A/g, the composite electrode retained 79.0% of its specific capacitance at 1 A/g, thus confirming its excellent rate performance. An asymmetric supercapacitor (ASC) with a wider potential window and higher energy density was assembled by using 3 M KOH as the electrolyte, the CoTe@rGO electrode as the positive electrode, and active carbon as the negative electrode. The operating voltage of the supercapacitor could be increased to 1.6 V, and its specific capacitance could reach 112.6 F/g at 1 A/g. The specific capacitance retention rate of the fabricated supercapacitor after 5000 charge/discharge cycles at 5 A/g was 87.1%, which confirms its excellent cycling stability. In addition, the ASC revealed a high energy density of 40.04 W·h/kg at a power density of 799.91 W/kg and a high power density of 4004.93 W/kg at an energy density of 33.43 W·h/kg. These results collectively show that CoTe@rGO materials have broad application prospects.

Co3S4/NiCo2S4 Nano-Arrays on Nickel Foam as Energy Storage for Supercapacitors

2021 ◽  
Vol 16 (6) ◽  
pp. 891-904
Author(s):  
Xiang-Sen Meng ◽  
Jun Xiang ◽  
Nan Bu ◽  
Yan Guo ◽  
Sroeurb Loy ◽  
...  
Keyword(s):  
Energy Storage ◽  
Energy Density ◽  
Electrochemical Performance ◽  
Specific Capacitance ◽  
Current Density ◽  
Retention Rate ◽  
Nickel Foam ◽  
Maximum Energy ◽  
Capacity Retention ◽  
A Current

In this work, Co3S4/NiCo2S4 nano-arrays electrode with Co3S4 nanocones and NiCo2S4 nanosheets interlaced arrangement are prepared by the promising hydrothermal method. Compared with single Co3S4/NF or NiCo2S4/NF electrode, the prepared Co3S4/NiCo2S4/NF electrode exhibits excellent specific capacitance. At a current density of 2 mA cm−2, the surface capacitance is as high as 9036 mF cm−2, and it still maintains a surface capacitance of 5664 mF cm−2 at a current density of 8 mA cm−2. Co3S4/NiCo2S4/NF||ASC has a high electrochemical performance with a maximum energy density of 0.62 Wh cm−3 and a power density of 15.94 W cm−3. At a current density of 5 mA cm−2, the capacity retention rate is 83.75% after 3000 cycles.

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