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Related Concept Videos

Newman Projections02:06

Newman Projections

Different notations are used to represent the three-dimensional structure of molecules on two-dimensional surfaces. One of the most commonly used representations is the dash-wedge formula. The dashed wedges, solid wedges, and the plane lines indicate the groups situated behind the plane, coming out of the plane, and in the plane, respectively.
The organic molecules rotate across the single bonds leading to numerous temporary three-dimensional structures of varying energy known as conformers.
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Adsorption is a process where molecules, known as the adsorbates, accumulate on a surface, which is referred to as the adsorbent or substrate. Occurring at the solid-gas interface, this phenomenon is crucial in various scientific and industrial contexts. The reverse of adsorption is desorption.Two types of adsorptions exist: physical (physisorption) and chemical (chemisorption). Physisorption involves gas molecules held to the solid's surface by relatively weak intermolecular van der Waals...
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Adsorption isotherms are mathematical models that describe how molecules in a gas or liquid phase interact with surfaces. Two of the most common isotherm models are the Langmuir and Freundlich isotherms, which relate to Type I monolayer chemisorption. The Langmuir model is based on four key assumptions:• Adsorption cannot exceed monolayer coverage.• All surface sites are equivalent.• Molecules adsorb only at vacant sites.• There are no interactions between adsorbed molecules.Consider the...
Adsorption Isotherms II01:25

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Surface Properties of Synthesized Nanoporous Carbon and Silica Matrices
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Published on: March 27, 2019

Adsorption-Energy Distribution of Heterogeneous Surfaces Predicted by Projections onto Convex Sets.

Thomas Hocker1, Grigoriy L. Aranovich, Marc D. Donohue

  • 1Department of Chemical Engineering, The Johns Hopkins University, Baltimore, Maryland, 21218

Journal of Colloid and Interface Science
|May 15, 2001
PubMed
Summary

The projection onto convex sets (POCS) method effectively calculates adsorption-energy distributions from adsorption integrals for heterogeneous surfaces. This robust technique provides reliable solutions for adsorption-integral inversions, even with experimental errors.

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Area of Science:

  • Physical Chemistry
  • Surface Science
  • Computational Chemistry

Background:

  • Adsorption-energy distribution functions are crucial for understanding surface phenomena.
  • Energetically heterogeneous surfaces present challenges in accurately determining these distributions.
  • Existing methods may struggle with experimental noise and a priori constraint integration.

Purpose of the Study:

  • To apply the Projection Onto Convex Sets (POCS) method for calculating adsorption-energy distribution functions.
  • To assess the efficacy of POCS in inverting adsorption integrals for heterogeneous surfaces.
  • To demonstrate the robustness of POCS in handling experimental errors.

Main Methods:

  • Utilized the Projection Onto Convex Sets (POCS) method.
  • Employed a modified Langmuir local isotherm within the adsorption integral.
  • Incorporated experimental data, measurement error information, and a priori constraints (e.g., nonnegativity).

Main Results:

  • Successfully calculated adsorption-energy distribution functions from adsorption integrals.
  • Demonstrated that POCS yields feasible solutions consistent with all constraints.
  • Showcased excellent recovery of energy distributions from simulated adsorption data with errors.

Conclusions:

  • The POCS method is a valuable and reliable tool for adsorption-integral inversions.
  • POCS offers a robust approach for determining adsorption-energy distributions on heterogeneous surfaces.
  • The method's ability to integrate constraints and handle errors enhances its applicability.