scholarly journals Dispersion-mediated steering of organic adsorbates on a precovered silicon surface

2018 ◽  
Vol 14 ◽  
pp. 2715-2721 ◽  
Author(s):  
Lisa Pecher ◽  
Sebastian Schmidt ◽  
Ralf Tonner
Keyword(s):  
Pattern Formation ◽  
Silicon Surface ◽  
Surface Adsorption ◽  
Semiconductor Surface ◽  
Limiting Factor ◽  
Dispersion Interactions ◽  
Covalently Bonded ◽  
Pauli Repulsion ◽  
Organic Adsorbates ◽  
Determining Factor

The chemistry of organic adsorbates on surfaces is often discussed in terms of Pauli repulsion as limiting factor regarding the packing of molecules. Here we show that the attractive part of the van der Waals potential can be similarly decisive. For the semiconductor surface Si(001), an already covalently bonded molecule of cyclooctyne steers a second incoming molecule via dispersion interactions onto the neighbouring adsorption site. This helps in understanding the nonstatistical pattern formation for this surface–adsorbate system and hints toward an inclusion of dispersion attraction as another determining factor for surface adsorption.

scholarly journals Peculiarities of Morphology Formation of Silicon Surface under the Action of Laser Pulses

2017 ◽  
Vol 18 (3) ◽  
pp. 309-312
Author(s):  
O.Yu. Bonchyk ◽  
S.G. Kiyak ◽  
I.A. Mohylyak ◽  
D.I. Popovych
Keyword(s):  
Crystallographic Orientation ◽  
Silicon Surface ◽  
Crystal Surface ◽  
Periodic Structures ◽  
Experimental Studies ◽  
Laser Pulses ◽  
Semiconductor Surface ◽  
Microscopic Studies ◽  
Millisecond Laser

The experimental studies of geometry features of silicon layers in areas of second and millisecond laser pulses were carried out. The results of microscopic studies of periodic structures that are formed on the surfaces with crystallographic orientation (111) (110) (100) and on planes, cut at an angle of 6° to the plane (100) and amorphous layers В2О3 deposited on the surface of silicon were presented. The results can be used to determine the crystallographic orientation of the semiconductor surface and express assessment of disorientation degree of crystal surface.

scholarly journals An Efficient and Accurate Model for Water with an Improved Non-Bonded Potential

2020 ◽  
Author(s):  
Mohamad Mohebifar ◽  
Christopher Rowley
Keyword(s):  
Liquid Water ◽  
Computational Cost ◽  
Type Model ◽  
Dispersion Interactions ◽  
Jones Potential ◽  
Decay Potential ◽  
Pauli Repulsion ◽  
Higher Order Dispersion ◽  
Experimental Density ◽  
Good Agreement

A molecular mechanical model for liquid water is developed that uses a physically-motivated potential to represent Pauli repulsion and dispersion instead of the standard Lennard-Jones potential. The model has three-atomic sites and a virtual site located on the ∠HOH bisector (i.e., a TIP4P-type model). Pauli-repulsive interactions are represented using a Buckingham-type exponential decay potential. Dispersion interactions are represented by both and terms. This higher order dispersion term has been neglected by most force fields. The ForceBalance code was used to define parameters that optimally reproduce the experimental physical properties of liquid water. The resulting model is in good agreement with the experimental density, dielectric constant, enthalpy of vaporization, isothermal compressibility, thermal expansion coefficient, diffusion coefficient, and radial distribution function. A GPU-accelerated implementation of this improved non-bonded potential can be employed in OpenMM without modification by using the CustomNonBondedForce feature. Efficient and automated parameterization of these non-bonded potentials provides a rational strategy to define a new molecular mechanical force field that treats repulsion and dispersion interactions more rigorously without major modifications to existing simulation codes or a substantially larger computational cost.

scholarly journals An Efficient and Accurate Model for Water with an Improved Non-Bonded Potential

2020 ◽  
Author(s):  
Mohamad Mohebifar ◽  
Christopher Rowley
Keyword(s):  
Liquid Water ◽  
Computational Cost ◽  
Type Model ◽  
Dispersion Interactions ◽  
Jones Potential ◽  
Decay Potential ◽  
Pauli Repulsion ◽  
Higher Order Dispersion ◽  
Experimental Density ◽  
Good Agreement

A molecular mechanical model for liquid water is developed that uses a physically-motivated potential to represent Pauli repulsion and dispersion instead of the standard Lennard-Jones potential. The model has three-atomic sites and a virtual site located on the ∠HOH bisector (i.e., a TIP4P-type model). Pauli-repulsive interactions are represented using a Buckingham-type exponential decay potential. Dispersion interactions are represented by both and terms. This higher order dispersion term has been neglected by most force fields. The ForceBalance code was used to define parameters that optimally reproduce the experimental physical properties of liquid water. The resulting model is in good agreement with the experimental density, dielectric constant, enthalpy of vaporization, isothermal compressibility, thermal expansion coefficient, diffusion coefficient, and radial distribution function. A GPU-accelerated implementation of this improved non-bonded potential can be employed in OpenMM without modification by using the CustomNonBondedForce feature. Efficient and automated parameterization of these non-bonded potentials provides a rational strategy to define a new molecular mechanical force field that treats repulsion and dispersion interactions more rigorously without major modifications to existing simulation codes or a substantially larger computational cost.

Enhanced Pool Boiling Using Carbon Nanotube Arrays on a Silicon Surface

2005 ◽  
Author(s):  
Sebastine O. Ujereh ◽  
Issam Mudawar ◽  
Placidius B. Amama ◽  
Timothy S. Fisher ◽  
Weilin Qu
Keyword(s):  
Heat Transfer ◽  
Heat Flux ◽  
Carbon Nanotube ◽  
Integrated Circuit ◽  
Silicon Surface ◽  
Pool Boiling ◽  
Limiting Factor ◽  
High Heat Flux ◽  
Transfer Coefficients ◽  
Chip Surface

Progress in integrated circuit technology has caused device density and power dissipation to increase, resulting in significant cooling challenges. Pool boiling is an attractive cooling option because of its unique combination of passive fluid circulation and high heat flux capability. Having no mechanical pumps, pool boiling hardware is less complex, easier to seal, and free of pump-induced fluid pulsations that are present with many alternative approaches. One of the main obstacles for improvements in pool boiling technology is the limiting factor of critical heat flux (CHF), which limits cooling capacity. The present experimental work considers the introduction of carbon nanotube (CNT) arrays on the chip surface to delay CHF and to enhance boiling heat transfer. Pool boiling curves for a smooth silicon surface and a silicon surface coated with CNTs were obtained. Tests were conducted in which power was input in 1 W increments to the respective silicon surfaces immersed in FC-72 fluid. These experiments reveal significant boiling enhancement. Testing reveals a measured CHF of approximately 15 W/cm2 for a CNT-coated silicon wafer and a CHF of approximately 10 W/cm2 for bare silicon wafers. Further, superheat at fully developed boiling is reduced on CNT-coated surfaces by up to 60%, and effective heat transfer coefficients are enhanced by approximately 400% by the presence of CNTs.

scholarly journals THE EFFECT OF SURFACE TENSION ON FREE-SURFACE FLOW INDUCED BY A POINT SINK

2016 ◽  
Vol 57 (4) ◽  
pp. 417-428
Author(s):  
G. C. HOCKING ◽  
H. H. N. NGUYEN ◽  
L. K. FORBES ◽  
T. E. STOKES
Keyword(s):  
Surface Tension ◽  
Free Surface ◽  
Axisymmetric Flow ◽  
Free Surface Flow ◽  
Surface Flow ◽  
Limiting Factor ◽  
Inviscid Fluid ◽  
Steady Solutions ◽  
Determining Factor ◽  
Effect Of Surface

The steady, axisymmetric flow induced by a point sink (or source) submerged in an inviscid fluid of infinite depth is computed and the resulting deformation of the free surface is obtained. The effect of surface tension on the free surface is determined and is the new component of this work. The maximum Froude numbers at which steady solutions exist are computed. It is found that the determining factor in reaching the critical flow changes as more surface tension is included. If there is zero or a very small amount of surface tension, the limiting factor appears to be the formation of small wavelets on the free surface; but, as the surface tension increases, this is replaced by a tendency for the lowest point on the free surface to descend sharply as the Froude number is increased.

Stochastic resonance in a realistic model for surface adsorption

Open Physics ◽  
2012 ◽  
Vol 10 (3) ◽  
Author(s):  
J. Sierra ◽  
Horacio Wio
Keyword(s):  
Pattern Formation ◽  
Stochastic Resonance ◽  
Surface Adsorption ◽  
Realistic Model ◽  
Bistable System ◽  
Approximation Methods ◽  
Lateral Interactions ◽  
Pressure Oscillations ◽  
State Approximation ◽  
Micro Reactors

AbstractWe study a model for a monolayer single adsorbate system used to describe pattern formation on adsorbates with lateral interactions, when it is submitted to pressure oscillations. Through numerical and analytical (based on a two-state approximation) methods to analyze the existence of stochastic resonance in such a bistable system. This is a first step toward the study of resonant phenomena in adsorbate systems with moving fronts and/or with presence of micro-reactors or spots.

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