scholarly journals Comparison of the Stability of 2H Nanosurfaces by the Adsorption of Small Molecules : A DFT Study

2021 ◽  
pp. 122-129
Author(s):  
Alev Sakarya ◽  
Seyfettin Dalgic ◽  
Serap Senturk Dalgic
Keyword(s):  
Small Molecules ◽  
Recovery Time ◽  
Density Functional ◽  
Hexagonal Phase ◽  
Gold Surface ◽  
Dft Method ◽  
Absorption Energy ◽  
Short Recovery Time ◽  
The Stability ◽  
2D Nanosheets

Density functional theory (DFT) calculations were carried out to understand the structural stability of 2D nanosheets of gold and silver in hexagonal phase of 2H by the adsorption of small molecules. In this work, we have obtained the bonding and adsorption properties of such small molecules as H2O, H2O2, and C2H5OH on 2H phase of gold and silver nanosurfaces, through DFT method using Quantum Expresso (QE) code. The high absorption energy values of (-2.45 eV, -2,46 eV, -2, 41 eV) for H2O, H2O2, and C2H5OH molecules on 2H-Au surfaces, respectively obtained than that of 2H-silver surfaces that the interaction between small molecules and both 2H nanosurfaces corresponds to physisorption. However, during the adsorption, the gold surface in the 2H phase (2H-Au) seems to preserve its atomic structure, while 2H-Ag surface changes from 2H to the fcc structure. Based on the analysis of electronic and physicochemical properties, the composite systems of 2H-gold/2H-silver-small molecules exhibit semiconductor behaviour. While 2H-Ag surfaces have short recovery time values for hydrogen peroxide (H2O2), this time is quite long for 2H-Au surfaces. Because of the long recovery time, Au-2H reported surfaces can be a candidate for possible applications of viral capture. Thus, the reported results are significant, and they would stimulate the experimental and further studies.

Ru-decorated gallium nitride nanotubes as chemical sensor for detection of purinethol drug: a density functional theory study

2021 ◽  
Author(s):  
A. A. Menazea ◽  
Nasser S. Awwad ◽  
Hala Ibrahium ◽  
Parvaneh delirkheirollahinezhad ◽  
H. Elhosiny Ali
Keyword(s):  
Recovery Time ◽  
Density Functional ◽  
Chemical Sensor ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Water Solvent ◽  
Highly Sensitive ◽  
Short Recovery Time ◽  
The Impact ◽  
Sensing Performance

Abstract We employed density functional B3LYP to inspect the impact of Ru-decoration on a GaN nanotube (GaNNT) sensing performance in detection of purinethol (PT) drug. The interaction of the pristine GaNNT with the PT was found to be weak, and the sensing response is 4.3. Decorating an Ru atom into the GaNNT surface increases the adsorption energy (Ead) of PT from -6.5 to -23.6 kcal/mol. The sensing response significantly rises to 93.6 by Ru-decoration. A short recovery time of 15.7 s is found for the PT desorption from the Ru-decorated GaNNT surface at 298 K. The water solvent reduces Ead of PT to -20.1 kcal/mol. Thus, it suggests that Ru-decorated GaNNT may be a highly sensitive PT sensor with a short recovery time.

Phase Stability Study of the Shape Memory Alloy CuAl-X (X: Be, Zn, Ti, Ni, Ag and Au) by Ab Initio Calculations

2016 ◽  
Vol 879 ◽  
pp. 250-255
Author(s):  
Nassim Boudalia ◽  
Jean Marc Raulot ◽  
Etienne Patoor ◽  
Claude Esling
Keyword(s):  
Density Functional Theory ◽  
Shape Memory Alloys ◽  
Shape Memory ◽  
First Principles ◽  
Density Functional ◽  
Dft Method ◽  
Stability Study ◽  
Atomic Scale ◽  
Functional Theory ◽  
The Stability

Shape memory alloys (SMA) have been at the forefront of research in recent years. They have been used for a wide variety of applications in various fields. This work presents a brief study at the atomic scale of Cu-Al based Shape Memory Alloys. Using first-principles Density Functional Theory (DFT) method, the stability of different austenitic and martensitic phases of Cu3Al, the effect of intrinsic vacancies, the doping effect by an element X (X = Be, Zn, Ti, Ni, Ag and Au) have been studied.

Stability and Electronic Structures of Mg2Pb (100), (110) and (111) Surfaces

2015 ◽  
Vol 817 ◽  
pp. 690-697
Author(s):  
Yong Hua Duan ◽  
Yong Sun ◽  
Ming Jun Peng
Keyword(s):  
Density Functional Theory ◽  
Surface Energy ◽  
Density Of States ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Charge Density Difference ◽  
The Stability

The stability and electronic properties of Mg2Pb (100), (110) and (111) surfaces were investigated by using the first-principles density functional theory (DFT) method. The calculated results showed that the orders of relaxation and surface energy are |∆d15(111)| < |∆d15(110)| < |∆d15(100)| andEsurf(100) >Esurf(110) >Esurf(111), respectively, indicating that Mg2Pb (111) surface is the most stable among these three low index surfaces. The Density of states (DOS) of Mg2Pb surfaces are mainly dominated by Pb-6, Mg-3s, and 2porbitals in the band ranging from-5 eV to Fermi level. It can be further obtained from results of the DOS and the charge density difference that Mg2Pb (111) surface is more stable than Mg2Pb (100) and (110) surfaces. The Mg2Pb (111) surface is the thermodynamically most favorable over all of the range of.

Investigation of the Adsorption Rubraca Anticancer Drug on the CNT(4,4-8) Nanotube as a Factor of Drug Delivery: A Theoretical Study Based on DFT Method

2019 ◽  
Vol 19 (7) ◽  
pp. 473-486 ◽  
Author(s):  
Masoome Sheikhi ◽  
Siyamak Shahab ◽  
Mehrnoosh Khaleghian ◽  
Mahin Ahmadianarog ◽  
Fatemeh Azarakhshi ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Dft Method ◽  
Nbo Analysis ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Adsorption Effect ◽  
Chemical Shift Tensors ◽  
Td Dft ◽  
The Stability

Background: In the present study, the interaction between new drug Rubraca and CNT(4,4-8) nanotube by Density Functional Theory (DFT) calculations in an aqueous medium for first time have been investigated. Method and Results: According to calculations, the intermolecular hydrogen bonds take place between active positions of the molecule Rubraca and hydrogen atoms of the nanotube that plays an important role in the stability of the complex CNT(4,4- 8)/Rubraca. The non-bonded interaction effects of the molecule Rubraca with CNT(4,4- 8) nanotube on the electronic properties, chemical shift tensors and natural charge have been also detected. The natural bond orbital (NBO) analysis suggested that the molecule Rubraca as an electron donor and the CNT(4,4-8) nanotube plays the role an electron acceptor at the complex CNT(4,4-8)/Rubraca. The electronic spectra of the Rubraca drug and the complex CNT(4,4-8)/Rubraca were also calculated by Time Dependent Density Functional Theory (TD-DFT) for the investigation of adsorption effect of the Rubraca drug over nanotube. Conclusion: The use of CNT(4,4-8) nanotube for Rubraca delivery to the diseased cells have been established.

scholarly journals Orbital Analysis of Natural Bonds, Calculations of the Functional Theory of Density Time-Dependent and Absorption Spectral of a Series of Rhodanine Derivatives

2020 ◽  
Vol 10 (5) ◽  
pp. 453
Author(s):  
Koffi Alexis Respect Kouassi ◽  
Anoubilé Benié ◽  
Kouakou Nobel N’guessan ◽  
Mamadou Guy-Richard Koné ◽  
Adenidji Ganiyou ◽  
...  
Keyword(s):  
Density Functional ◽  
Local Density ◽  
Dft Method ◽  
Energy Difference ◽  
Exchange Capacity ◽  
Nucleophilic Attack ◽  
Electronic Density ◽  
Functional Theory ◽  
Preferential Site ◽  
The Stability

<p>In this work, the density functional theory (DFT) method at the B3LYP/6-31 + G (d, p) level has used to determine the optimization of five rhodanine derivatives. The stability of the derivatives (7a-7e) of 5-arylidene rhodanine, the hyperconjugative interactions, the delocalization of the atomic charges was analyzed with the analysis of the Natural Bond Orbital (NBO). The electronic structures were discussed and the relocation of electronic density was determined. Molecular Electrostatic Potential (MEP), local density functional descriptors, border molecular orbitals and absorption spectrum were studied. Through the local Fukui reactivity indices, the carbon of the carbonyl group (C = O) is the preferential site of the nucleophilic attack and the sulfur atom linked to the trigonal carbon (C = S) is the preferential site of electrophile attack. Analysis of the global descriptors revealed that compound 7c is the most reactive with an energy difference between the frontier orbitals of ΔEgap = 3.305 eV. Furthermore, this compound 7c is the less stable, the softest and has the greatest electronic exchange capacity of all studied compounds. The intramolecular electronic transitions which stabilize these compounds are LP → π * for 7a and 7d and σ → σ * for 7b, 7c and 7e. The rhodanine derivatives are more reactive and more soluble in polar solvents.</p>

scholarly journals Theoretical Investigation of Br2 and Cl2 Detection by the Pristine and Co-Doped Graphyne

2021 ◽  
Author(s):  
Mohammad Reza Poor Heravi
Keyword(s):  
Density Functional Theory ◽  
Electrical Resistance ◽  
Recovery Time ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Time Value ◽  
Short Recovery Time ◽  
Homo Lumo ◽  
Co Doped

Abstract The Br2 and Cl2 interaction with the intrinsic, and Co-doped graphyne nanosheets has been explored by density functional theory calculations. Two vertical and parallel configurations were identified for Br2 and Cl2 adsorption. Calculations showed that the adsorption of Br2 was stronger than Cl2 on the graphyne nanosheet. Neither Br2 nor Cl2 could make serious changes to the HOMO-LUMO gap (Eg) and electrical resistance pf pristine sheet. By manipulating the structure of pristine graphyne by Co atom, its reactivity and sensitivity dramatically improved toward Br2 and Cl2 gases. Compared to the Cl2, the Br2 much more decreases the electrical resistance and Eg of the Co-doped graphyne (~ -40.25%). Thus, the Co-doped graphyne may selectively recognize the Br2 gas in the presence of Cl2. The computed recovery time value for Br2 from the surface of the Co-doped graphyne is 36.4 s, which shows that the graphyne, as a sensor, benefits from a short recovery time to detect Br2.

scholarly journals Radiation-Induced Oxidation Reactions of 2-Selenouracil in Aqueous Solutions: Comparison with Sulfur Analog of Uracil

Molecules ◽  
2021 ◽  
Vol 27 (1) ◽  
pp. 133
Author(s):  
Konrad Skotnicki ◽  
Ireneusz Janik ◽  
Klaudia Sadowska ◽  
Grazyna Leszczynska ◽  
Krzysztof Bobrowski
Keyword(s):  
Absorption Band ◽  
Absorption Spectra ◽  
Density Functional ◽  
Transient Absorption ◽  
Dft Method ◽  
Transient Absorption Spectrum ◽  
Oxidation Reactions ◽  
Radiation Induced ◽  
High Concentrations ◽  
The Stability

One-electron oxidation of 2-selenouracil (2-SeU) by hydroxyl (●OH) and azide (●N3) radicals leads to various primary reactive intermediates. Their optical absorption spectra and kinetic characteristics were studied by pulse radiolysis with UV-vis spectrophotometric and conductivity detection and by the density functional theory (DFT) method. The transient absorption spectra recorded in the reactions of ●OH with 2-SeU are dominated by an absorption band with an λmax = 440 nm, the intensity of which depends on the concentration of 2-SeU and pH. Based on the combination of conductometric and DFT studies, the transient absorption band observed both at low and high concentrations of 2-SeU was assigned to the dimeric 2c-3e Se-Se-bonded radical in neutral form (2●). The dimeric radical (2●) is formed in the reaction of a selenyl-type radical (6●) with 2-SeU, and both radicals are in equilibrium with Keq = 1.3 × 104 M−1 at pH 4 (below the pKa of 2-SeU). Similar equilibrium with Keq = 4.4 × 103 M−1 was determined for pH 10 (above the pKa of 2-SeU), which admittedly involves the same radical (6●) but with a dimeric 2c-3e Se-Se bonded radical in anionic form (2●−). In turn, at the lowest concentration of 2-SeU (0.05 mM) and pH 10, the transient absorption spectrum is dominated by an absorption band with an λmax = 390 nm, which was assigned to the ●OH adduct to the double bond at C5 carbon atom (3●) based on DFT calculations. Similar spectral and kinetic features were also observed during the ●N3-induced oxidation of 2-SeU. In principle, our results mostly revealed similarities in one-electron oxidation pathways of 2-SeU and 2-thiouracil (2-TU). The major difference concerns the stability of dimeric radicals with a 2c-3e chalcogen-chalcogen bond in favor of 2-SeU.

Structure, Stability and Water Adsorption on Ultra-Thin TiO2 Supported on TiN

2019 ◽  
Author(s):  
Jose Julio Gutierrez Moreno ◽  
Marco Fronzi ◽  
Pierre Lovera ◽  
alan O'Riordan ◽  
Mike J Ford ◽  
...  
Keyword(s):  
Density Functional ◽  
Water Adsorption ◽  
Chemical Potential ◽  
Energy Gap ◽  
Molecular Water ◽  
Structure Stability ◽  
Ambient Conditions ◽  
Rutile Structure ◽  
The Stability ◽  
The One

<p></p><p>Interfacial metal-oxide systems with ultrathin oxide layers are of high interest for their use in catalysis. In this study, we present a density functional theory (DFT) investigation of the structure of ultrathin rutile layers (one and two TiO<sub>2</sub> layers) supported on TiN and the stability of water on these interfacial structures. The rutile layers are stabilized on the TiN surface through the formation of interfacial Ti–O bonds. Charge transfer from the TiN substrate leads to the formation of reduced Ti<sup>3+</sup> cations in TiO<sub>2.</sub> The structure of the one-layer oxide slab is strongly distorted at the interface, while the thicker TiO<sub>2</sub> layer preserves the rutile structure. The energy cost for the formation of a single O vacancy in the one-layer oxide slab is only 0.5 eV with respect to the ideal interface. For the two-layer oxide slab, the introduction of several vacancies in an already non-stoichiometric system becomes progressively more favourable, which indicates the stability of the highly non-stoichiometric interfaces. Isolated water molecules dissociate when adsorbed at the TiO<sub>2</sub> layers. At higher coverages the preference is for molecular water adsorption. Our ab initio thermodynamics calculations show the fully water covered stoichiometric models as the most stable structure at typical ambient conditions. Interfacial models with multiple vacancies are most stable at low (reducing) oxygen chemical potential values. A water monolayer adsorbs dissociatively on the highly distorted 2-layer TiO<sub>1.75</sub>-TiN interface, where the Ti<sup>3+</sup> states lying above the top of the valence band contribute to a significant reduction of the energy gap compared to the stoichiometric TiO<sub>2</sub>-TiN model. Our results provide a guide for the design of novel interfacial systems containing ultrathin TiO<sub>2</sub> with potential application as photocatalytic water splitting devices.</p><p></p>

Thermodynamic Stability of Hexagonal and Rhombohedral Bn at Cvd Conditions from Van der Waals Corrected First Principles Calculations

2019 ◽  
Author(s):  
Henrik Pedersen ◽  
Björn Alling ◽  
Hans Högberg ◽  
Annop Ektarawong
Keyword(s):  
Thin Films ◽  
Thermodynamic Stability ◽  
First Principles ◽  
Thermal Equilibrium ◽  
Density Functional ◽  
Van Der Waals ◽  
Chemical Vapor ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Stability

Thin films of boron nitride (BN), particularly the sp<sup>2</sup>-hybridized polytypes hexagonal BN (h-BN) and rhombohedral BN (r-BN) are interesting for several electronic applications given band gaps in the UV. They are typically deposited close to thermal equilibrium by chemical vapor deposition (CVD) at temperatures and pressures in the regions 1400-1800 K and 1000-10000 Pa, respectively. In this letter, we use van der Waals corrected density functional theory and thermodynamic stability calculations to determine the stability of r-BN and compare it to that of h-BN as well as to cubic BN and wurtzitic BN. We find that r-BN is the stable sp<sup>2</sup>-hybridized phase at CVD conditions, while h-BN is metastable. Thus, our calculations suggest that thin films of h-BN must be deposited far from thermal equilibrium.

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