THE sp HYBRID BONDING OF C, N AND O TO THE fcc(001) SURFACE OF NICKEL AND RHODIUM

2000 ◽  
Vol 07 (03) ◽  
pp. 347-363 ◽  
Author(s):  
CHANG Q. SUN
Keyword(s):  
Driving Force ◽  
Electrostatic Force ◽  
Bond Formation ◽  
Technical Innovation ◽  
Hollow Site ◽  
Strong Bond ◽  
Orbital Hybridization ◽  
Host Atom ◽  
Initial Stage ◽  
Valence Electrons

This brief review focuses on the nature, kinetics, dynamics and consequences of the sp-orbital hybrid bonding of C, N and O to the Ni/Rh(001) surfaces which give rise to the same kind of "radial and then the p4g clock" reconstruction. It is identified that the "radial" and the subsequent "clock" reconstruction result from the adsorbate–substrate bond formation with sp-orbital hybridization, and that the driving force behind the reconstruction originates from the electrostatic interaction along the <11> direction. At the initial stage, A-1 (A=C, N or O adsorbate) sinks into the fourfold hollow site and forms one bond with a B (B = Ni or Rh host atom) underneath, giving rise to an AB5 cluster with four dipoles at the surface. As A-1 evolves into the hybridized-A-n (n=4, 3, 2), the AB5 cluster evolves into an AB4 tetrahedron. Meanwhile, the AB4 tetrahedron redefines three of the four surface dipoles as B+, B2+, B+/ dipole or Bdipole, depending on the valence value of the adsorbate. The electrostatic force arises upon repopulating the valence electrons, which creates rhombus strings along the <11> direction. With the presence of nonbonding lone pairs, the clock rotation on Ni(00l)-(2×2)p4g-2N-3 and Rh(00l)-(2×2)p4g-2O-2 surfaces is initiated by the alternate attraction and repulsion in the <11> direction and the rotation is stabilized by bond tension; whereas the clock rotation on the Ni(00l)-(2×2)p4g-2C-4 surface is driven by the nonequivalent electrostatic repulsion in the <11> direction and the rotation is balanced by strong bond compression. The findings so far have led to technical innovation for the adhesion between diamond and metals by designing a gradient TiCN transition layer to neutralize the bond stress.

DRIVING FORCE AND BOND STRAIN FOR THE C–Ni(100) SURFACE REACTION

1999 ◽  
Vol 06 (01) ◽  
pp. 109-114 ◽  
Author(s):  
CHANG Q. SUN ◽  
PETER HING
Keyword(s):  
Driving Force ◽  
Surface Reaction ◽  
Charge Redistribution ◽  
Hollow Site ◽  
One Dimensional ◽  
Orbital Hybridization ◽  
Initial Stage ◽  
Bond Strain ◽  
Atomic States ◽  
Monolayer Coverage

It is shown that the atomic states, bonding dynamics, driving force and bond strain for the C–Ni(100) surface reaction can be consistently understood by considering the sp orbital hybridization of carbon. It is proposed that, at the initial stage, C sinks into the hollow site and bonds to one Ni atom underneath. The C -1 polarizes and pushes its surface neighbors radially away from the site center, and hence a Ni 5 C cluster forms. Then, sp hybridization of the C happens, leading to a Ni 4 C tetrahedron. Besides the Ni + underneath the C adsorbate, three of the four surface Ni neighbors donate electrons to the adsorbate. The half-monolayer coverage of C defines therefore half of the surface Ni atoms to be Ni + ions and the other half to be Ni 2+ ions. As a result, one-dimensional nonuniform "- (+) - (2+) – (2+) - (+) – (+) -" chains form along the < 11> direction. It is suggested that the forces arising from charge redistribution drive the reconstruction. Calculation reveals that an increase of ~ 90 dyne electrostatic repulsion along the < 11> direction and a responding ~ 130 dyne bond compression stabilize the network of (2× 2)p4g clock rotation.

Driving Force Behind the O-Rh(001) Clock Reconstruction

1998 ◽  
Vol 12 (20) ◽  
pp. 849-857 ◽  
Author(s):  
Chang Q. Sun
Keyword(s):  
Driving Force ◽  
Electrostatic Force ◽  
Bond Formation ◽  
Lone Pair ◽  
Atomic Ratio ◽  
Recent Model ◽  
Dual Roles ◽  
Low Energy Electron Diffraction ◽  
Dipole Interactions ◽  
Low Energy Electron

A novel rhombi-chain network is derived from low energy electron diffraction experimental observations and the recent model theory, revealing that the O-Rh(100) clock-rotation is driven by an electrostatic force arisen from bond formation. Thus the O-Rh bond suffers from tension other than compression, or strain relief. As O -1 evolves into the hybridized- O -2,a Rh 5 O cluster in the c(2 × 2) phase develops into a Rh 4 O tetrahedron and yields the overall (2 × 2)p4g reconstruction. In the (2 × 2)p4g phase, the hollow-sited O -2 defines one Rh + ion and two lone-pair-induced Rh dipoles of its four surface neighbors. The surface atomic ratio (O : Rh = 1 : 2) allocates, therefore, half of the surface Rh atoms to be the Rh dipoles and another half to play dual roles of Rh + ion and Rh dipole. Interactions along the "dipole–dipole – Rh +/dipole – Rh +/dipole" strings create the rhombi-chain at the <11> directions, and a responding bond tension confines the (2 × 2)p4g clock rotation.

scholarly journals Молекулярно-динамическое исследование влияния концентрации вакансий на скорость миграции границ наклона в никеле

2021 ◽  
Vol 63 (5) ◽  
pp. 582
Author(s):  
Г.М. Полетаев ◽  
Р.Ю. Ракитин
Keyword(s):  
Free Volume ◽  
Driving Force ◽  
Migration Rate ◽  
Vacancy Concentration ◽  
High Angle ◽  
Vacancy Clusters ◽  
Method Of Molecular Dynamics ◽  
Initial Stage ◽  
Tilt Boundaries ◽  
Mobile Vacancy

The influence of vacancy concentration on the migration rate of high-angle tilt boundaries with misorientation axes <111> and <100> in nickel was studied by the method of molecular dynamics. It is shown that the dependence of the migration rate on the concentration of vacancies introduced at the initial stage of modeling has a maximum near 1%. The decrease in the migration rate with a further increase in the free volume is mainly due to the deceleration of the boundary by low-mobile vacancy clusters, which at high vacancy concentrations the boundary is no longer capable of sorbing. The second reason for the decrease in the migration rate with an increase in the concentration of vacancies above 1% is a decrease in the surface tension of grain boundaries and, accordingly, the driving force of their migration due to the finite sorption capacity of the boundaries with respect to the excess free volume.

scholarly journals A Novel Capacitive Sensing Principle for Microdevices

2015 ◽  
Author(s):  
Jian Zhou ◽  
Ronald N. Miles ◽  
Shahrzad Towfighian
Keyword(s):  
Electric Field ◽  
Driving Force ◽  
Design Principle ◽  
Electrostatic Force ◽  
Low Cost ◽  
Repulsive Force ◽  
Attractive Force ◽  
Sensor Design ◽  
Capacitive Sensing

Conventional capacitive sensing places significant limitations on the sensor design due to the pull-in instability caused by the electrostatic force. The main purpose of this study is to examine a low-cost novel capacitive sensing principle based on electrostatic balance which promises to avoid these design limitations. The approach uses an asymmetric electric field on a structure with fingers that can generate a repulsive force while the gap is low and create an attractive force while the gap is large. The size and thickness of the fingers are also responsible for creating repulsive or attractive forces on the structure. This approach has recently been applied successfully in the design of capacitive actuators to provide a repulsive driving force. A new design principle for capacitive sensing is described that avoids pull-in instability by designing the fingers such that the structure is at the equilibrium.

scholarly journals Investigation of Interfacial Layer for Friction Stir Scribe Welded Aluminum to Steel Joints

2018 ◽  
Vol 140 (11) ◽  
Author(s):  
Kaifeng Wang ◽  
Piyush Upadhyay ◽  
Yuxiang Wang ◽  
Jingjing Li ◽  
Xin Sun ◽  
...  
Keyword(s):  
Electron Microscopy ◽  
Driving Force ◽  
Bond Formation ◽  
Welding Process ◽  
High Strength ◽  
Bimaterial Interface ◽  
Joint Interface ◽  
Friction Stir ◽  
Transmission Electron ◽  
Steel Joints

Friction stir scribe (FSS) welding as a recent derivative of friction stir welding (FSW) has been successfully used to fabricate a linear joint between automotive Al and steel sheets. It has been established that FSS welding generates a hook-like structure at the bimaterial interface. Beyond the hook-like structure, there is a lack of fundamental understanding on the bond formation mechanism during this newly developed FSS welding process. In this paper, the microstructures and phases at the joint interface of FSS welded Al to ultra-high-strength steel were studied using scanning electron microscopy (SEM) and transmission electron microscopy (TEM). It was found that both mechanical interlocking and interfacial bonding occurred simultaneously during the FSS welding process. Based on SEM observations, a higher diffusion driving force in the advancing side was found compared to the retreating side and the scribe swept zone, and thermally activated diffusion was the primary driving force for the interfacial bond formation in the scribe swept region. The TEM energy-dispersive X-ray spectroscopy (EDXS) revealed that a thin intermetallic compound (IMC) layer was formed through the interface, where the thickness of this layer gradually decreased from the advancing side to the retreating side owing to different material plastic deformation and heat generations. In addition, the diffraction pattern (or one-dimensional fast Fourier transform (FFT) pattern) revealed that the IMC layer was composed of Fe2Al5 or Fe4Al13 with a Fe/Al solid solution depending on the weld regions.

Thermodynamics of metal-ligand bond formation. XXV. Addition of bases to Bis[O,O'-diethyl thiomalonato]nickel(II) in various solvents

1977 ◽  
Vol 30 (3) ◽  
pp. 495 ◽  
Author(s):  
L Ang ◽  
DP Graddon ◽  
VAK Ng
Keyword(s):  
Thermodynamic Data ◽  
Driving Force ◽  
Bond Formation ◽  
Adduct Formation ◽  
Calorimetric Measurements ◽  
Carbon Tetra ◽  
Metal Ligand ◽  
Ligand Bond

Thermodynamic data have been obtained from spectroscopic and calorimetric measurements for the addition of pyridine and 4- methylpyridine to bis(O,O?-diethyl thiomalonato)nickel(II), Ni(etm)2, in solution in cyclohexane, benzene, 1,2-dichloroethane, acetonitrile, butan-2-one and carbon tetra-chloride. In each solvent two base molecules add successively, giving Ni(etm)2B then Ni(etm)2B2. There are only small variations in K1 and K2 in different solvents; typically K1 ≈ 200, K2 ≈ 100 l. mol-1, ΔH�1+2 ≈ -65, ΔH�2 ≈ 0 kJ mol-1 at 30�C, but in benzene and cyclohexane ΔH�2 ≈ -25 and in cyclohexane ΔH�1+2 ≈ -100 kJ mol-1. The main driving force for adduct formation is apparently the formation of the first Ni-N bond, which is accompanied by a spin change.

Empirical Studies on Demand Pull in Photovoltaic Sector of Twenty Countries

2013 ◽  
Vol 827 ◽  
pp. 451-456
Author(s):  
Mo Lin Huo ◽  
Bao Guo Shan
Keyword(s):  
Large Scale ◽  
Empirical Studies ◽  
Technical Innovation ◽  
Practical Significance ◽  
Small Scale ◽  
Market Growth ◽  
Demand Pull ◽  
Initial Stage ◽  
Acceleration Period ◽  
Diffusion Rates

High cost impedes large-scale deployment of photovoltaics (PV), and the technical innovation is one of most important factors of cost reduction, so how to accelerate the market pull for innovation has practical significance and theoretical value. This paper aims to analyze PV demand pull mechanism based on empirical evidence. According to the features of PV industry and technical innovation theories, make hypotheses of PV market pull and the relationship between diffusion rates and the market pull. Then propose testing method of the market pull and the coefficients assessing diffusion rates, and use historical data of twenty countries to conduct empirical studies. The testing results show that 70% of PV market in the twenty countries pulled technical innovation; at the initial stage of PV diffusion, the market pull was insignificant when the market kept at small scale and the diffusion rate can be indicated by the innovation coefficient; in the acceleration period, the market pull was insignificant when the market grew steeply and the rate can be indicated by the imitating coefficient. So in order to encourage demand pull, policy making is suggested to lead the market growth stable and sustained.

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