A DENSITY FUNCTIONAL STUDY OF THE STRUCTURE OF SILANE COUPLING AGENT 3–AMINOPROPYLTRIETHOXYSILANE

2005 ◽  
Vol 04 (01) ◽  
pp. 117-126
Author(s):  
N. L. MA ◽  
P. WU
Keyword(s):  
Coupling Agent ◽  
Density Functional ◽  
Solution Structure ◽  
Silane Coupling Agent ◽  
Industrial Applications ◽  
Functional Study ◽  
Stable Form ◽  
Functional Theory ◽  
Silane Coupling ◽  
The Stability

Using density functional theory, we predicted the solution structure of the hydrolyzed 3–aminopropyltriethoxysilane (h–APS), which is a silane coupling agent commonly used in many industrial applications. We have located five stable minima on the potential energy surface of h–APS in which four of them are "neutral", and the remaining one is zwitterionic (dipolar) in nature. Our calculations suggested that the stability of the most stable form of h–APS in water (denoted as II_N) arose from strong intramolecular OH ⋯ N hydrogen bond. The least stable form is the zwitterionic form (I_ZW), which is estimated to be over 90 kJ mol -1 less stable than II_N. The factors governing the relative stabilities of different forms are discussed.

ELECTRONIC STRUCTURES AND THE STABILITY OF MgO SURFACE: DENSITY FUNCTIONAL STUDY

2015 ◽  
Vol 22 (03) ◽  
pp. 1550037 ◽  
Author(s):  
DIAN-NA ZHANG ◽  
LI ZHAO ◽  
JIA-FU WANG ◽  
YAN-LI LI
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Chemical Potential ◽  
Surface States ◽  
Functional Study ◽  
Functional Theory ◽  
Calculation Results ◽  
The Stability ◽  
Mgo Surface

The electronic structures and the stability of the low-index surface (001), (011) and (111) for MgO were investigated by first-principles method based on density functional theory (DFT). We analyzed the stability of the MgO slab in equilibrium with an arbitrary oxygen environment. The density of states (DOS) and the band structures of MgO slabs were calculated and compared with those of the bulk MgO . Our calculation results reveal that the stabilities of the surface vary with the change of O chemical potential. In addition, the (001) and (011) surfaces are semiconductors, which are similar to that of the bulk MgO . However, the MgO (111) surface exhibits metallic property due to the effect of the surface states, which is different from that of the bulk MgO .

scholarly journals Enhancement in Adhesive and Thermal Properties of Bio-based Epoxy Resin by Using Eugenol Grafted Cellulose Nanocrystals

2021 ◽  
Author(s):  
Tariq Aziz Tariq ◽  
Jieyuan Zheng ◽  
Muhammad Imran Jamil ◽  
Hong Fan ◽  
Roh Ullah ◽  
...  
Keyword(s):  
Cellulose Nanocrystals ◽  
Coupling Agent ◽  
Epoxy Resins ◽  
Silane Coupling Agent ◽  
Industrial Applications ◽  
Environment Friendly ◽  
H Nmr ◽  
Naturally Occurring ◽  
Silane Coupling ◽  
Surface Morphologies

Abstract Bio-based epoxy resins are being used due to their green chemistry. They have better properties than petroleum-based epoxy resins. Recently, environment friendly nanomaterials have been used for different industrial applications. Cellulose nanocrystals (CNCs) are among the best naturally occurring materials. Therefore, the surface of cellulose nanocrystals are modified by eugenol-based silane coupling agent (EBSCA). Chemical composition and surface morphologies of CNCs were analyzed and characterized by FTIR, AFM, SEM, TEM and 1H-NMR. The SEM and AFM results confirmed eugenol-based silane coupling agent was successfully grafted on cellulose nanocrystals. Modified CNCs demonstrated an excellent tensile strength (2190 MPa) and modulus (16.00 MPa), as well as storage modulus (1622 MPa) exhibited by 1wt% modified cellulose nanocrystals composites. Additionally, modified CNCs displayed hydrophobic behavior (CA=102 ± 2°). The corresponding modified CNCs have significant applications in combination of high stiffness and strength to the epoxy resins. This study lays a foundation towards full bio-based, environment friendly polymers fabrication and consumptions most desirable in adhesive and mechanical industrial fields.

Influence of defect pairs in Ga-based ordered defect compounds: a hybrid density functional study

2020 ◽  
Vol 98 (8) ◽  
pp. 770-777
Author(s):  
Sudhir Kumar ◽  
Suman Joshi ◽  
Durgesh Kumar Sharma ◽  
Sushil Auluck
Keyword(s):  
Band Gap ◽  
Energy Band ◽  
Density Functional ◽  
Functional Study ◽  
Energy Band Gap ◽  
Functional Theory ◽  
Lattice Constants ◽  
Donor Acceptor ◽  
The Stability ◽  
Hybrid Density Functional

In the present paper, density functional theory (DFT) based calculations have been performed to predict the stability, electronic, and optical properties of Ga-rich ordered defect compounds (ODCs). The calculated lattice constants, bulk modulus, their pressure derivatives, and optical constants show good agreement with available experimental data. The hybrid exchange correlations functional have been considered to calculate ground state total energy and energy band gap of the material. The calculated formation energy of ODCs comes smaller than pure CuGaSe2 (CGS). Our calculated optical absorption coefficients indicate that the energy band gap of ODCs can be tuned by changing the number of donor–acceptor defect pairs ([Formula: see text]). The band offset has been calculated to understand the reason of band gap alteration while the number of defect pair changes. Our results may be helpful for other experiments to further improve the performance of ODCs.

DENSITY FUNCTIONAL STUDY ON THE EFFECT OF ELECTRON WITHDRAWING SUBSTITUENT ON THE STABILITY OF RNHBH2

2009 ◽  
Vol 08 (01n02) ◽  
pp. 53-56
Author(s):  
DONG HYUN JUNG ◽  
DAEJIN KIM ◽  
AREUM LEE ◽  
SEUNG-HOON CHOI ◽  
SANG OOK KANG
Keyword(s):  
Density Functional Theory ◽  
Bond Strength ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Functional Study ◽  
Functional Theory ◽  
Similar Tendency ◽  
Charge Analysis ◽  
Electron Withdrawal ◽  
The Stability

We investigated the stability of aminoborane with electron withdrawing groups such as – CF 3 and – CN using density functional theory calculations. For the electron withdrawing groups of – CF 3 and – CN , we observed similar tendency of B – N bond strength: electron withdrawal from the N atom reduces the strength of B – N bonds. And we find that the electron density localized on B and N is also reduced through the charge analysis. These electron withdrawing substituents make cyclic dimers and trimers stabilized less than electron donating ones.

scholarly journals Geometry, tautomerism and non-covalent interactions of the drug halofuginone with the carbon-nanotube and γ-Fe2O3 nanoparticles: A DFT study

2018 ◽  
Vol 83 (3) ◽  
pp. 305-315
Author(s):  
Shima Kazeri-Shandiz ◽  
Ali Beyramabadi ◽  
Ali Morsali
Keyword(s):  
Density Functional ◽  
Noncovalent Interactions ◽  
Single Wall Carbon Nanotubes ◽  
Stable Form ◽  
Fe2o3 Nanoparticles ◽  
Functional Theory ◽  
Pcm Model ◽  
Energy Behavior ◽  
Non Covalent Interactions ◽  
The Stability

Halofuginone is a potential anti-malarial drug, which could exist as three possible tautomers. Herein, using density functional theory (DFT), and handling the solvent effects with the PCM model, the tautomerism of halofuginone was investigated. Intramolecular H-bonds play an important role in the stability of the tautomers. The conformer H1a is the most stable. Noncovalent interactions of the H1a conformer with the armchair (5,5) single-wall carbon nanotubes and ?-Fe2O3 nanoparticles were explored in several manners. The most stable form of them was determined. The intermolecular H-bonds play a substantial role in the energy behavior of the interaction between ?-Fe2O3 nanoparticles and halofuginone.

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.

A Combined ab initio and Density Functional Study of the Electronic Structure of Thymine and 2-Thiothymine Radicals

2003 ◽  
Vol 68 (12) ◽  
pp. 2322-2334 ◽  
Author(s):  
Robert Vianello ◽  
Zvonimir B. Maksić
Keyword(s):  
Ab Initio ◽  
Spin Density ◽  
Density Functional ◽  
Radical Cations ◽  
Functional Study ◽  
Theory Approach ◽  
Functional Theory ◽  
Adiabatic Ionization Potential ◽  
Highest Occupied Molecular Orbital ◽  
Positively Charged

The electronic and energetic properties of thymine (1) and 2-thiothymine (2) and their neutral and positively charged radicals are considered by a combined ab initio and density functional theory approach. It is conclusively shown that ionization of 1 and 2 greatly facilitates deprotonation of the formed radical cations thus making the proton transfer between charged and neutral precursor species thermodynamically favourable. The adiabatic ionization potential of 1 and 2 are analysed. It appears that ADIP(1) is larger than ADIP(2) by 10 kcal/mol, because of greater stability of the highest occupied molecular orbital (HOMO) of the former. It is also shown beyond any doubt that the spin density in neutral and cationic radical of 2 is almost exclusively placed on the σ-3p AO of sulfur implying that these two systems represent rather rare sigma-radicals. In contrast, the spin density of radicals of 1 is distributed over their π-network.

Site preference and atomic ordering in the ternary Rh5Ga2As: first-principles calculations

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Nilanjan Roy ◽  
Sucharita Giri ◽  
Harshit ◽  
Partha P. Jana
Keyword(s):  
Total Energy ◽  
First Principles ◽  
Density Functional ◽  
Structure Type ◽  
Site Preference ◽  
X Ray Diffraction ◽  
Atomic Ordering ◽  
Functional Theory ◽  
The Stability ◽  
Bonding Characteristics

Abstract The site preference and atomic ordering of the ternary Rh5Ga2As have been investigated using first-principles density functional theory (DFT). An interesting atomic ordering of two neighboring elements Ga and As reported in the structure of Rh5Ga2As by X-ray diffraction data only is confirmed by first-principles total-energy calculations. The previously reported experimental model with Ga/As ordering is indeed the most stable in the structure of Rh5Ga2As. The calculation detected that there is an obvious trend concerning the influence of the heteroatomic Rh–Ga/As contacts on the calculated total energy. Interestingly, the orderly distribution of As and Ga that is found in the binary GaAs (Zinc-blende structure type), retained to ternary Rh5Ga2As. The density of states (DOS) and Crystal Orbital Hamiltonian Population (COHP) are calculated to enlighten the stability and bonding characteristics in the structure of Rh5Ga2As. The bonding analysis also confirms that Rh–Ga/As short contacts are the major driving force towards the overall stability of the compound.

Sign in / Sign up

Export Citation Format

Share Document