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.

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.

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.

Role of the Kinetic Relation in a Phase Transition-Based Model for Mechanical Unfolding in Macromolecules

2010 ◽  
Author(s):  
Ritwik Raj ◽  
Prashant K. Purohit
Keyword(s):  
Phase Transition ◽  
Driving Force ◽  
Metastable States ◽  
Force Extension ◽  
Kinetic Relation ◽  
One Dimensional ◽  
Applied Tension ◽  
Thermodynamic Driving Force ◽  
Macro Molecule

We present applications of a model developed to describe unfolding in macromolecules under an axial force. We show how different experimentally observed force-extension behaviors can be reproduced within a common theoretical framework. We propose that the unfolding occurs via the motion of a folded/unfolded interface along the length of the molecule. The molecules are modeled as one-dimensional continua capable of existing in two metastable states under an applied tension. The interface separates these two metastable states and represents a jump in stretch, which is related to applied force by the worm-like-chain relation. The mechanics of the interface are governed by the Abeyaratne-Knowles theory of phase transitions. The thermodynamic driving force controls the motion of the interface via an equation called the kinetic relation. By choosing an appropriate kinetic relation for the unfolding conditions and the macro-molecule under consideration, we have been able to generate a variety of unfolding processes in macromolecules.

scholarly journals Bacterial Phosphating of Mild (Unalloyed) Steel

2000 ◽  
Vol 66 (10) ◽  
pp. 4389-4395 ◽  
Author(s):  
Hans-Peter Volkland ◽  
Hauke Harms ◽  
Beat Müller ◽  
Gernot Repphun ◽  
Oskar Wanner ◽  
...  
Keyword(s):  
Oxygen Consumption ◽  
Iron Oxides ◽  
Driving Force ◽  
Steel Surface ◽  
Surface Reaction ◽  
Bacterial Activity ◽  
Initial Value ◽  
Steel Surfaces ◽  
Steel Electrodes ◽  
Unalloyed Steel

ABSTRACT Mild (unalloyed) steel electrodes were incubated in phosphate-buffered cultures of aerobic, biofilm-formingRhodococcus sp. strain C125 and Pseudomonas putida mt2. A resulting surface reaction leading to the formation of a corrosion-inhibiting vivianite layer was accompanied by a characteristic electrochemical potential (E) curve. First, E increased slightly due to the interaction of phosphate with the iron oxides covering the steel surface. Subsequently, E decreased rapidly and after 1 day reached −510 mV, the potential of free iron, indicating the removal of the iron oxides. At this point, only scattered patches of bacteria covered the surface. A surface reaction, in which iron was released and vivianite precipitated, started. E remained at −510 mV for about 2 days, during which the vivianite layer grew steadily. Thereafter, E increased markedly to the initial value, and the release of iron stopped. Changes in E and formation of vivianite were results of bacterial activity, with oxygen consumption by the biofilm being the driving force. These findings indicate that biofilms may protect steel surfaces and might be used as an alternative method to combat corrosion.

The Adsorption Mechanism of Sodium Lignosulfonate on Al2O3 Particle in the Aqueous Solution

2012 ◽  
Vol 550-553 ◽  
pp. 1120-1123
Author(s):  
Rong Li ◽  
Dong Jie Yang ◽  
Wen Yuan Guo ◽  
Xue Qing Qiu
Keyword(s):  
Aqueous Solution ◽  
Hydrogen Bond ◽  
Driving Force ◽  
Adsorption Mechanism ◽  
Hydrophobic Interactions ◽  
Adsorption Properties ◽  
Sodium Lignosulfonate ◽  
Ph Values ◽  
Electrostatic And Hydrophobic Interactions ◽  
Monolayer Coverage

The adsorption properties of sodium lignosulfonate (SL) on Al2O3 particles under different pH values have been investigated. Results show that at low pHs, SL adsorbs on the Al2O3 particles in the form of aggregate as dosage of SL increases; at high pHs, the adsorption is approximately monolayer coverage. With pH values ranging from 3 to 11, the adsorption results are found to be not significantly affected by the addition of urea, ruling out the hydrogen bond as the controlling factor. The paper demonstrates that the main driving force of adsorption is considered as the synergistic effect of electrostatic and hydrophobic interactions when pH pHIEP with additives of Na2SO4 and NaCl.

scholarly journals The nematocyst's sting is driven by the tubule moving front

2017 ◽  
Vol 14 (128) ◽  
pp. 20160917 ◽  
Author(s):  
Sinwook Park ◽  
Gadi Piriatinskiy ◽  
Dan Zeevi ◽  
Jonathan Ben-David ◽  
Gilad Yossifon ◽  
...  
Keyword(s):  
Osmotic Potential ◽  
Microfluidic System ◽  
Injection Rate ◽  
Injection System ◽  
Predator Prey ◽  
One Dimensional ◽  
Initial Stage ◽  
Proposed Model ◽  
Injection Mechanism ◽  
Moving Front

The nematocyst is the explosive injection system of the phylum Cnidaria, and is one of the fastest delivery systems found in Nature. Exploring its injection mechanism is key for understanding predator–prey interactions and protection against jellyfish stinging. Here we analyse the injection of jellyfish nematocysts and ask how the build-up of the poly-γ-glutamate (pγGlu) osmotic potential inside the nematocyst drives its discharge. To control the osmotic potential, we used a two-channel microfluidic system to direct the elongating nematocyst tubule through oil, where no osmotic potential can develop, while keeping the nematocyst capsule in water at all times. In addition, the flow inside the tubule and the pγGlu concentration profiles were calculated by applying a one-dimensional mathematical model. We found that tubule elongation through oil is orders of magnitude slower than through water and that the injection rate of the nematocyst content is reduced. These results imply that the capsule's osmotic potential is not sufficient to drive the tubule beyond the initial stage. Our proposed model shows that the tubule is pulled by the high osmotic potential that develops at the tubule moving front. This new understanding is vital for future development of nematocyst-based systems such as osmotic nanotubes and transdermal drug delivery.

scholarly journals Parametrically Driven One-Dimensional Sine-Gordon Equation and Chaos

1988 ◽  
Vol 43 (8-9) ◽  
pp. 727-733
Author(s):  
B. M. Herbst ◽  
W.-H. Steeb
Keyword(s):  
Driving Force ◽  
Gordon Equation ◽  
Zero Mode ◽  
Space Structure ◽  
Chaotic Behaviour ◽  
Force Frequency ◽  
Sine Gordon Equation ◽  
Mode Structure ◽  
One Dimensional ◽  
The One

AbstractThe chaotic behaviour of the parametrically driven one-dimensional sine-Gordon equation with periodic boundary conditions is studied. The initial condition is u(x, 0) = ƒ(x), ut (x, 0) = 0 where ƒ is the breather solution of the one-dimensional sine-Gordon equation at t = 0. We vary the amplitude of the driving force, the frequency of the driving force and the damping constant. For appropriate values of the driving force, frequency and damping constant chaotic behaviour with respect to the time-evolution of w(x = fixed, t) can be found. The space structure u(t = fixed, x) changes with increasing driving force from a zero mode structure to a breather-like structure consisting of a few modes.

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