DFT modeling of the relative affinity of nitrogen ligands for trivalent f elements: an energetic point of view

The photodegradation mechanism of 1-phenyl-4-allyl-tetrazol-5-one has been studied using (time-dependent) density functional theory with the M06-HF, B3LYP, and PBE0 functionals and the VDZ basis set. All calculations have been carried out using the polarizable continuum model to simulate the solvent effects of methanol. The reaction pathway evolution on the triplet state has been characterised to validate a previously postulated experimental-based mechanism. The transition states and minimums have been initially located by local scanning in partial constrained optimisation, followed by a fully relaxed search procedure. The UV spectra has shown to be better described with PBE0 functional when compared with the experimental results, having the M06-HF a shift of 40 nm. From the energetic point of view, the postulated mechanism has been validated in this work showing a concerted photoextrusion of the N2 molecule. The intramolecular proton transfer occurs at a later stage of the mechanism after cyclization of the allyl group on a triplet biradical intermediate. The photoproduct observed experimentally, a pyrimidinone, has been characterised. The infrared spectroscopic reaction profile has also been proposed.

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A 6-Components Mechanistic Model of Cutting Actions in Milling

10.21203/rs.3.rs-1114156/v1 ◽

2021 ◽

Author(s):

Maël Jeulin ◽

Olivier Cahuc ◽

Philippe Darnis ◽

Raynald Laheurte

Keyword(s):

Energy Balance ◽

Experimental Model ◽

Cutting Forces ◽

Mechanistic Model ◽

Cutting Parameters ◽

Point Of View ◽

Stress Fields ◽

Mechanistic Modelling ◽

Cutting Zone ◽

Energetic Point

Abstract Most of the cutting models developed in the literature attest only to the presence of cutting forces in the balance of mechanical actions resulting from cutting. However, several studies have highlighted the presence of cutting moments during machining, and particularly 3D cutting in milling. The objective of this paper is to characterise phenomena associated with cutting moments by performing experimental mechanistic modelling in 3D cutting. For this purpose, several modelling factors will be investigated, such as the 3D cutting reference frame, the undeformed chip section, the cutting parameters, the cutting zone, etc. The predictive model of this study proves to be relatively efficient for an experimental model and allows a global prediction of cutting moments in milling. Furthermore, beyond the aspect of stress fields in the workpiece caused by cutting moments, this paper gives perspectives from an energetic point of view for which the share of moments in the energy balance could be substantial for monobloc tools.

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Investigation on the Intake Process for a Theoretical Twin Opposite Piston Compressor Using R744 Refrigerant

Applied Mechanics and Materials ◽

10.4028/www.scientific.net/amm.823.75 ◽

2016 ◽

Vol 823 ◽

pp. 75-78

Author(s):

Doru Groza ◽

Dan Mihai Dogariu

Keyword(s):

Air Conditioning ◽

Piston Compressor ◽

Environmental Issues ◽

Point Of View ◽

Vapor Compression ◽

Household Appliances ◽

Intake Process ◽

Vapor Compression Refrigeration ◽

Energetic Point ◽

Air Conditioning Systems

This study aims to validate the use of R744 for a resonant twin piston compressor for domestic applications. The vapor-compression refrigeration is the most commonly approached method for cooling household appliances such as refrigerators and air conditioning systems. The R134a refrigerant is one of the most suitable refrigerants from an energetic point of view. R744 (CO2) compressors are less efficient, but the fact that the R134a raises serious environmental issues pushes commercial trend towards the usage of R744 [1]-[3]. Use of R744 in household appliances is currently an open topic and no company has switched yet to the environmental-friendly alternative. In this paper the fill efficiency will be simulated in order to validate if a conventional compressor such as the opposite twin piston compressor is capable of filling with refrigerant when operating at a 50Hz frequency. Such a validation can enable further investigations regarding the replacement of R134a with R744.

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DFT Visualization and Experimental Evidence of BHT-Mg-Catalyzed Copolymerization of Lactides, Lactones and Ethylene Phosphates

Polymers ◽

10.3390/polym11101641 ◽

2019 ◽

Vol 11 (10) ◽

pp. 1641 ◽

Cited By ~ 3

Author(s):

Ilya Nifant’ev ◽

Andrey Shlyakhtin ◽

Maxim Kosarev ◽

Dmitry Gavrilov ◽

Stanislav Karchevsky ◽

...

Keyword(s):

Ring Opening ◽

Density Functional ◽

Point Of View ◽

Basis Set ◽

Random Copolymers ◽

Key Factors ◽

Functional Theory ◽

Cyclic Esters ◽

Dft Modeling ◽

Derivatives Of

Catalytic ring-opening polymerization (ROP) of cyclic esters (lactides, lactones) and cyclic ethylene phosphates is an effective way to process materials with regulated hydrophilicity and controlled biodegradability. Random copolymers of cyclic monomers of different chemical nature are highly attractive due to their high variability of characteristics. Aryloxy-alkoxy complexes of non-toxic metals such as derivatives of 2,6-di-tert-butyl-4-methylphenoxy magnesium (BHT-Mg) complexes are effective coordination catalysts for homopolymerization of all types of traditional ROP monomers. In the present paper, we report the results of density functional theory (DFT) modeling of BHT-Mg-catalyzed copolymerization for lactone/lactide, lactone/ethylene phosphate and lactide/ethylene phosphate mixtures. ε-Caprolactone (ε-CL), l-lactide (l-LA) and methyl ethylene phosphate (MeOEP) were used as examples of monomers in DFT simulations by the Gaussian-09 program package with the B3PW91/DGTZVP basis set. Both binuclear and mononuclear reaction mechanistic concepts have been applied for the calculations of the reaction profiles. The results of calculations predict the possibility of the formation of random copolymers based on l-LA/MeOEP, and substantial hindrance of copolymerization for ε-CL/l-LA and ε-CL/MeOEP pairs. From the mechanistic point of view, the formation of highly stable five-membered chelate by the products of l-LA ring-opening and high donor properties of phosphates are the key factors that rule the reactions. The results of DFT modeling have been confirmed by copolymerization experiments.

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Simulation and Field Experiments With an Agricultural Tractor of a Robust Control for a Complete Fluid Power Circuit Using a New Electro-Hydraulic Pump: Part II—Control

ASME 2010 10th Biennial Conference on Engineering Systems Design and Analysis, Volume 5 ◽

10.1115/esda2010-25220 ◽

2010 ◽

Author(s):

Pandeli Borodani ◽

Davide Colombo ◽

Marco Forestello ◽

Patrizio Turco ◽

Riccardo Morselli

Keyword(s):

Field Experiments ◽

Optimization Techniques ◽

Point Of View ◽

Hydraulic Pump ◽

Power Circuit ◽

Control Approach ◽

New Device ◽

Displacement Pump ◽

Variable Displacement ◽

Energetic Point

The plant under control is the hydraulic circuit arranged by CNH in a prototype agriculture tractor of medium segment, where instead of the conventional main hydraulic pump, a new device electronically piloted, is installed. The main purpose is basically to obtain some advantages according to the energetic point of view, by means of an appropriate control structure, managing the electronic variable displacement pump. The frontier of the new systems requires the employment of the advanced control techniques, in order to assure the levels of precision, reliability, robustness demanded from systems. The control design methodology employed in the present case is based on robust H∞ optimization techniques, where robust stability properties are guaranteed in presence of unaccountable dynamics and other destabilizing factors. The effectiveness of the proposed control approach is tested on the demonstrative tractor realized from the CNH Agriculture at Modena plants, in all real conditions.

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Biomass conversion into valuable products within the integrated management of bio-resources

E3S Web of Conferences ◽

10.1051/e3sconf/20198507008 ◽

2019 ◽

Vol 85 ◽

pp. 07008 ◽

Cited By ~ 3

Author(s):

Gabriela Ionescu ◽

Cora Bulmău

Keyword(s):

Biomass Conversion ◽

Integrated Management ◽

Point Of View ◽

Biomass Waste ◽

Waste Valorisation ◽

Energetic Point ◽

Biomass Availability ◽

By Products

The present research proposes two scenarios for the biomass conversion into valuable products within the integrated management of bio-resources. The scenarios have been developed considering: the biomass availability, material and by-products characteristics and the comprehensive combination of the primary technologies used for the conversion of the biomass mixtures into energy. In scenario 1 the biomass waste valorisation is made via integrated pyrolysis and combustion treatment, while in scenario 2 the biomass conversion in done considering the integration of the pyrolysis, gasification and combustion treatments into the conversion chain. The results revealed that all analysed scenarios purposed are self-independent from the energetic point of view.

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Feasibility study of hydrogen-bonded nucleic acid base pairs in gas and water phases — A theoretical study

Canadian Journal of Chemistry ◽

10.1139/v11-124 ◽

2011 ◽

Vol 89 (11) ◽

pp. 1403-1409 ◽

Cited By ~ 17

Author(s):

S. Arshadi ◽

A.R. Bekhradnia ◽

A. Ebrahimnejad

Keyword(s):

Hydrogen Bonding ◽

Nucleic Acid ◽

Hydrogen Bonds ◽

Density Functional ◽

Biological Properties ◽

Point Of View ◽

Basis Set ◽

Base Pairs ◽

Bonding Properties ◽

Energetic Point

To investigate the base pair binding probabilities for nucleic acid bases, numerous models were studied for contacts between adenine, thymine, guanine, cytosine, and uracil using density functional theory (DFT) in combination with the 6–311G* basis set. We obtained an assessment for the energy given by our calculations in gas and aqueous phases, which showed that it should be incorporated into hydrogen bonding and propeller rotational energies. The 42 complexes of base pairs (5 regular and 37 irregular base pairs) were proposed and their hydrogen-bonding (H-bonding) properties were verified. The hydrogen bonds in some irregular base pairs, including CC, UU, and TT (series 1), were stronger than in regular GC and AT base pairs. Also, the strength of the hydrogen bonds in the proposed base pairs, including CU, GG, GU, and TU (series 2), were similar to regular base pairs from an energetic point of view. The propeller rotations revealed a higher rotational barrier energy (6–7.5 kcal/mol; 1 cal = 4.184 J) for irregular base pairs (series 1 and 2) than regular GC and AT ones (1–3 kcal/mol). Nevertheless, the trend in these affinities of the complex contact probabilities and their biological properties were confirmed by our calculations.

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Weak sulfur-sulfur interactions between chemically-identical atoms

Open Chemistry ◽

10.2478/s11532-012-0178-z ◽

2013 ◽

Vol 11 (3) ◽

pp. 457-463 ◽

Cited By ~ 4

Author(s):

Radu Silaghi-Dumitrescu ◽

Alexandru Lupan

Keyword(s):

Van Der Waals ◽

Interaction Force ◽

Molecular Orbitals ◽

Point Of View ◽

Attractive Interaction ◽

Theoretical Methods ◽

Energetic Point ◽

Van Der Waals Radii ◽

Simple Models

AbstractAbstract Experimentally-known sulfur-sulfur distances shorter than the sum of van der Waals radii and involving two chemically-identical sulfur atoms are examined at several levels of theory (BP86/6-31G** to CCSD(T)/6-311+G**). None of the theoretical methods predict an attractive interaction from an energetic point of view, even though molecular orbitals stretching between the two sulfur atoms have been identified. Most likely, if there is indeed an attractive interaction force between chemically identical sulfur atoms, its value is comparable to the accuracy of the methods employed here — implying an attractive interaction below 1 kcal/mol. The investigation includes some simple models of 1,6,12,17-tetrathiacyclodocosa-2,4,13,15-tetrayne which was previously shown to have an S—S interaction involving two chemically-identical atoms. Attractive interactions calculated for these latter models are shown to arise from S—HC weak bonding, with the S—S interaction being again repulsive. Graphical abstract

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Elastic and Electronic Properties of Mg2Ca and Mg2Y Phases

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.233-235.2231 ◽

2011 ◽

Vol 233-235 ◽

pp. 2231-2238 ◽

Cited By ~ 2

Author(s):

Meng Xue Zeng ◽

Bi Yu Tang ◽

Li Ming Peng ◽

Wen Jiang Ding

Keyword(s):

Mechanical Properties ◽

Electronic Properties ◽

Structural Stability ◽

Density Functional ◽

Elastic Anisotropy ◽

Underlying Mechanism ◽

Point Of View ◽

Electronic Density ◽

Energetic Point ◽

Two Phases

Elastic and electronic properties of Mg2Ca and Mg2Y phases were investigated from first-principles calculations based on density functional theory. The optimized lattice parameters were found to be in excellent agreement with the available experimental value, and the structural stability was also studied from the energetic point of view. The five independent elastic constants were calculated, then the bulk modulus B, shear modulus G, Young’s modulus E and Poisson’s ratio ν of polycrystalline aggregates were derived, and the relevant mechanical properties Mg2Ca and Mg2Y phases were also further discussed. The elastic anisotropy of the two phases was also discussed in details. Finally, the electronic density of states and charge density distribution were also calculated to reveal the underlying mechanism of structural stability and mechanical properties.

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A Laboratory Plant for Gas Liquefaction

International Journal of Air-Conditioning and Refrigeration ◽

10.1142/s2010132515500108 ◽

2015 ◽

Vol 23 (02) ◽

pp. 1550010 ◽

Cited By ~ 2

Author(s):

M. De Salve ◽

D. Milani ◽

B. Panella ◽

G. Roveta

Keyword(s):

High Speed ◽

Gas Flow ◽

Time History ◽

Gas Production ◽

Point Of View ◽

Plant Performance ◽

Condensation Process ◽

In Series ◽

Energetic Point ◽

Main Components

A prototype gas liquefaction plant has been designed and manufactured for Politecnico di Torino cryogenic laboratory and has been used for cryogenic applications like superconducting cables and low temperature refrigeration devices. The plant is able to liquefy nitrogen and, by means of little changes, hydrogen and other cryogenic fluids too. The thermal energy is removed by four high speed (up to 360 000 revolutions per minute) helium turbines that are connected in series. The gas liquefaction is carried out by the cooling condensation process of the gas flow that feeds a 0.15 m3 super insulated tank that is cooled inside. The cryogenic system is based on the Claude and Collins cycles, fed with helium that provides the cold sink. The paper shows the characteristics of the plant main components, and the time history of the measured temperatures, pressures, and flow rates during the plant start-up, as well as the steady state liquefied gas production rate. From the energetic point of view, the plant performance is acceptable for a research laboratory and the plant efficiency is not far from that of commercial larger size plants.

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