scholarly journals Theoretical Determination of Binding Energies of Small Molecules on Interstellar Ice Surfaces

2021 ◽  
Vol 8 ◽  
Author(s):  
Denis Duflot ◽  
Céline Toubin ◽  
Maurice Monnerville
Keyword(s):  
Carbon Atom ◽  
Small Molecules ◽  
Single Point ◽  
Binding Energies ◽  
Basis Sets ◽  
Adsorption Sites ◽  
Interstellar Ice ◽  
Amorphous Ices ◽  
Semi Empirical

The adsorption of a series of atoms and small molecules and radicals (H, C, N, O, NH, OH, H2O, CH3, and NH3) on hexagonal crystalline and amorphous ice clusters were obtained via classical molecular dynamics and electronic structure methods. The geometry and binding energies were calculated using a QMHigh:QMLow hybrid method on model clusters. Several combination of basis sets, density functionals and semi-empirical methods were compared and tested against previous works. More accurate binding energies were also refined via single point Coupled Cluster calculations. Most species, except carbon atom, physisorb on the surface, leading to rather small binding energies. The carbon atom forms a COH2 molecule and in some cases leads to the formation of a COH-H3O+ complex. Amorphous ices are characterized by slightly stronger binding energies than the crystalline phase. A major result of this work is to also access the dispersion of the binding energies since a variety of adsorption sites is explored. The interaction energies thus obtained may serve to feed or refine astrochemical models. The present methodology could be easily extended to other types of surfaces and larger adsorbates.

scholarly journals MgO Cluster Models for Capture CO2 Molecule

2020 ◽  
Vol 5 (8) ◽  
pp. 915-921
Author(s):  
Zinab Ibrahim Alhony ◽  
Fathi Hassan Bawa
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Binding Energies ◽  
Cluster Models ◽  
Basis Sets ◽  
Practical Applications ◽  
Adsorption Sites ◽  
Acidic Sites ◽  
Homo And Lumo ◽  
Carbonate Species

The density functional theory (DFT) method was used to study the adsorption of acidic CO2 molecule on the oxide clusters (MgO)n , (n = 2, 4, 6, 8, 9 and 12). Basis sets, 6–311 G, 6–311G (d) and 6–311G (2d) were employed in order to test the effect on adsorption structures and binding energies. Both  and adsorption sites have been considered. Our previous calculation DFT energies have been achieved for the (MgO)n, (CaO)n, (n = 1–4, 6, 8, 9, and 12 clusters), [WJERT, 2019, Vol.5, Issue 1, 328-341]. The present work investigates the adsorption properties (e.g., adsorption energies, geometries and HOMO and LUMO molecular orbitals) of a single CO2 molecule. The results show that the CO2 molecule / (MgO)n clusters prefer to adsorb as [Mg surf –  with one acidic sites, while the interaction with surface basic    sites, carbonate species consequently may occur. The HOMO and LUMO interaction between CO2 and MgO cluster models were also studied. Furthermore, such nanostructures systems can be potential candidates for practical applications of capturing CO2 from hot exhaust gases.

Quantitative determination of surface species and adsorption sites using Infrared spectroscopy

2016 ◽  
Vol 259 ◽  
pp. 19-26 ◽  
Author(s):  
Alan J. McCue ◽  
Greg A. Mutch ◽  
Andrew I. McNab ◽  
Steven Campbell ◽  
James A. Anderson
Keyword(s):  
Infrared Spectroscopy ◽  
Quantitative Determination ◽  
Surface Species ◽  
Adsorption Sites

scholarly journals DFT calculation and assignment of vibrational spectra of aryl and alkyl chlorophosphates

2014 ◽  
Vol 12 (2) ◽  
pp. 153-163
Author(s):  
Viktor Anishchenko ◽  
Vladimir Rybachenko ◽  
Konstantin Chotiy ◽  
Andrey Redko
Keyword(s):  
Vibrational Spectra ◽  
Basis Sets ◽  
Heavy Atoms ◽  
Wide Range ◽  
Complete Assignment ◽  
Key Factor ◽  
Polarization Functions ◽  
Experimental Values ◽  
Semi Empirical ◽  
Good Agreement

AbstractDFT calculations of vibrational spectra of chlorophosphates using wide range of basis sets and hybrid functionals were performed. Good agreement between calculated and experimental vibrational spectra was reached by the combination of non-empirical functional PBE0 with both middle and large basis sets. The frequencies of the stretching vibrations of the phosphate group calculated using semi-empirical functional B3LYP for all basis sets deviate significantly from the experimental values. The number of polarization functions on heavy atoms was shown to be a key factor for the calculation of vibrational frequencies of organophosphates. The importance of consideration of all the stable rotamers for a complete assignment of fundamental modes was shown.

The assessment of density functionals for DNA–protein stacked and T-shaped complexes

2010 ◽  
Vol 88 (8) ◽  
pp. 815-830 ◽  
Author(s):  
Lesley R. Rutledge ◽  
Stacey D. Wetmore
Keyword(s):  
Amino Acid ◽  
Potential Energy ◽  
Large Scale ◽  
Enzymatic Reaction ◽  
Basis Sets ◽  
Density Functionals ◽  
Interaction Energies ◽  
Π Interactions ◽  
Hybrid Techniques ◽  
Semi Empirical

The present work uses 129 nucleobase – amino acid CCSD(T)/CBS stacking and T-shaped interaction energies as reference data to test the ability of various density functionals with double-zeta quality basis sets, as well as some semi-empirical and molecular mechanics methods, to accurately describe noncovalent DNA–protein π–π and π+–π interactions. The goal of this work is to identify methods that can be used in hybrid approaches (QM/MM, ONIOM) for large-scale modeling of enzymatic systems involving active-site (substrate) π–π contacts. Our results indicate that AMBER is a more appropriate choice for the lower-level method in hybrid techniques than popular semi-empirical methods (AM1, PM3), and suggest that AMBER accurately describes the π–π interactions found throughout DNA–protein complexes. The M06–2X and PBE-D density functionals were found to provide very promising descriptions of the 129 nucleobase – amino acid interaction energies, which suggests that these may be the most suitable methods for describing high-level regions. Therefore, M06–2X and PBE-D with both the 6–31G(d) and 6–31+G(d,p) basis sets were further examined through potential-energy surface scans to better understand how these techniques describe DNA–protein π–π interactions in both minimum and nonminimum regions of the potential-energy surfaces, which is critical information when modeling enzymatic reaction pathways. Our results suggest that studies of stacked nucleobase – amino acid systems should implement the PBE-D/6–31+G(d,p) method. However, if T-shaped contacts are involved and (or) smaller basis sets must be considered due to limitations in computational resources, then M06–2X/6–31G(d) provides an overall excellent description of both nucleobase – amino acid stacking and T-shaped interactions for a range of DNA–protein π–π and π+–π interactions.

Preliminary Studies on the Determination of FLD for Single Point Incremental Sheet Metal Forming

2012 ◽  
Vol 504-506 ◽  
pp. 863-868 ◽  
Author(s):  
Miklos Tisza ◽  
Péter Zoltán Kovács ◽  
Zsolt Lukács
Keyword(s):  
Sheet Metal ◽  
Sheet Metal Forming ◽  
Metal Forming ◽  
New Technologies ◽  
Single Point ◽  
Research Work ◽  
Dimensional Accuracy ◽  
Forming Limit ◽  
Incremental Sheet Metal Forming

Development of new technologies and processes for small batch and prototype production of sheet metal components has a very important role in the recent years. The reason is the quick and efficient response to the market demands. For this reasons new manufacturing concepts have to be developed in order to enable a fast and reliable production of complex components and parts without investing in special forming machines. The need for flexible forming processes has been accelerated during the last 15 years, and by these developments the technology reaches new extensions. Incremental sheet metal forming (ISMF) may be regarded as one of the promising developments for these purposes. A comprehensive research work is in progress at the University of Miskolc (Hungary) to study the effect of important process parameters with particular emphasis on the shape and dimensional accuracy of the products and particularly on the formability limitations of the process. In this paper, some results concerning the determination of forming limit diagrams for single point incremental sheet metal forming will be described.

Self‐consistent molecular orbital methods. XVII. Geometries and binding energies of second‐row molecules. A comparison of three basis sets

1976 ◽  
Vol 64 (12) ◽  
pp. 5142-5151 ◽  
Author(s):  
John B. Collins ◽  
Paul von R. Schleyer ◽  
J. Stephen Binkley ◽  
John A. Pople
Keyword(s):  
Molecular Orbital ◽  
Binding Energies ◽  
Basis Sets ◽  
Self Consistent

Determination of the Effective Depth for Double-Fiber Fluorometric Sensors

1992 ◽  
Vol 46 (6) ◽  
pp. 919-924 ◽  
Author(s):  
Zhong Yuan Zhu ◽  
M. Cecilia Yappert
Keyword(s):  
Fiber Optic Sensor ◽  
Fluorescence Signal ◽  
Acceptance Angle ◽  
Fiber Sensors ◽  
Sample Depth ◽  
Effective Depth ◽  
Different Diameters ◽  
Semi Empirical ◽  
Analytical Expressions

The relationship between the relative fluorescence signal excited and collected with a double-fiber optic sensor and the sample depth has been investigated. The complexity of the analytical expressions for the relative fluorescence signal and the effective depth was reduced by deriving a set of semi-empirical equations which can be evaluated in a simple fashion. These expressions take into account the configuration of the sensor, i.e., fiber diameter, acceptance angle, and separation between fibers. The expressions were tested with the use of double-fiber sensors with different diameters and separations between fibers. The reduction of the effective depth in solutions with significant absorbance was evaluated.

A New Approach for Erosion Prediction Due To Fly Ash

1981 ◽  
Vol 103 (2) ◽  
pp. 265-270 ◽  
Author(s):  
R. Kotwal ◽  
W. Tabakoff
Keyword(s):  
Fly Ash ◽  
Gas Turbines ◽  
Precise Determination ◽  
Erosion Prediction ◽  
Industrial Gas Turbines ◽  
Series Of Experiments ◽  
A New Technique ◽  
Nickel Base ◽  
Semi Empirical

With increasing interest in the burning of coal in industrial gas turbines, there is also concern for the precise determination of the erosive effects on the turbine components. Series of experiments were conducted to determine the effects of fly ash constituents, particle size, particle velocity, angle of attack and target temperature on the erosion of iron and nickel base alloys. Based on the experimental results, a semi-empirical equation has been obtained for the prediction of the erosion losses. This equation provides a new technique for predicting the metal erosion due to the fly ash produced by the conventional burning of coal.

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