scholarly journals Quantum Chemistry Estimation of Adhesion Strength of Hydroxyapatite with Titanium Substrate

2021 ◽  
Vol 03 (04) ◽  
pp. 1-1
Author(s):  
Alla V. Balueva ◽  
◽  
Ilia N. Dashevskiy ◽  
Patricia Todebush ◽  
◽  
...  
Keyword(s):  
Adhesion Strength ◽  
Density Functional ◽  
Reaction Path ◽  
Titanium Substrate ◽  
Reaction Products ◽  
Functional Theory ◽  
Standard Material ◽  
The Difference ◽  
Ground Energy ◽  
Biocompatible Coatings

One of the ways to improve the fusion of an implant with bone tissue is through the use of biocompatible coatings, in particular, hydroxyapatite (HAp). It is important to assess the strength of the HAp adhesion to the implant. The measure of the strength of the bond of the coating with the substrate is the energy of this bond. Using density functional theory and molecular dynamics, the reaction path, reaction products, oscillation frequency, activation energy and bond energy between different combinations of component anions HAp and Ti (II) – the standard material of implants – are calculated. Using the computational chemistry software suite Gaussian 09 (Revision C.01 was used), the stable configurations of the reactants and products are found, and the binding energy of hydroxyapatite and titanium is then calculated based on the difference in ground energy of reactants and ground energy of products. Thus, the method of adhesion strength estimation between HAp coatings and Ti is proposed based on numerical calculations using MD software, and suggestions are provided on which conditions would be the best for optimal binding strength.

scholarly journals Molecular simulation on mechanism of thiophene hydrodesulfurization on surface of Ni2P

2021 ◽  
pp. 014459872199495
Author(s):  
Songjian Du ◽  
Tingting Li ◽  
Xinwei Wang ◽  
Liqiang Zhang ◽  
Zhengda Yang ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Reaction Mechanism ◽  
Heavy Oil ◽  
Density Functional ◽  
Reaction Path ◽  
Functional Theory ◽  
Thiophene Hydrodesulfurization ◽  
Cracking Reaction ◽  
Materials Studio ◽  
Optimal Reaction

Hydrodesulfurization reaction, as the last step of hydrothermal cracking reaction, is of great significance for the reduction of viscosity and desulfurization of heavy oil. Based on Density Functional Theory and using Dmol3 module of Materials Studio, this research simulated the adsorption and hydrodesulfurization of thiophene on Ni2P (001) surface, and discussed the hydrodesulfurization reaction mechanism of thiophene on Ni2P (001) surface. It was found that the direct hydrodesulfurization of thiophene had more advantages than the indirect hydrodesulfurization of thiophene. Finally, the optimal reaction path was determined: C4H4S+H2→C4H6.

scholarly journals Theoretical Study of the Structures of 4-(2,3,5,6-Tetrafluoropyridyl)Diphenylphosphine Oxide and Tris(Pentafluorophenyl)Phosphine Oxide: Why Does the Crystal Structure of (Tetrafluoropyridyl)Diphenylphosphine Oxide Have Two Different P=O Bond Lengths?

Molecules ◽  
2020 ◽  
Vol 25 (12) ◽  
pp. 2778
Author(s):  
Joseph R. Lane ◽  
Graham C. Saunders
Keyword(s):  
Crystal Structure ◽  
Hydrogen Bonding ◽  
Phosphine Oxide ◽  
Density Functional ◽  
Lone Pair ◽  
Diphenylphosphine Oxide ◽  
Functional Theory ◽  
Weak Hydrogen Bonding ◽  
Independent Molecules ◽  
The Difference

The crystal structure of 4-(2,3,5,6-tetrafluoropyridyl)diphenylphosphine oxide (1) contains two independent molecules in the asymmetric unit. Although the molecules are virtually identical in all other aspects, the P=O bond distances differ by ca. 0.02 Å. In contrast, although tris(pentafluorophenyl)phosphine oxide (2) has a similar crystal structure, the P=O bond distances of the two independent molecules are identical. To investigate the reason for the difference, a density functional theory study was undertaken. Both structures comprise chains of molecules. The attraction between molecules of 1, which comprises lone pair–π, weak hydrogen bonding and C–H∙∙∙arene interactions, has energies of 70 and 71 kJ mol−1. The attraction between molecules of 2 comprises two lone pair–π interactions, and has energies of 99 and 100 kJ mol−1. There is weak hydrogen bonding between molecules of adjacent chains involving the oxygen atom of 1. For one molecule, this interaction is with a symmetry independent molecule, whereas for the other, it also occurs with a symmetry related molecule. This provides a reason for the difference in P=O distance. This interaction is not possible for 2, and so there is no difference between the P=O distances of 2.

scholarly journals Application of β-Phosphorylated Nitroethenes in [3+2] Cycloaddition Reactions Involving Benzonitrile N-Oxide in the Light of a DFT Computational Study

Organics ◽  
2021 ◽  
Vol 2 (1) ◽  
pp. 26-37
Author(s):  
Karolina Zawadzińska ◽  
Karolina Kula
Keyword(s):  
Density Functional ◽  
Reaction Path ◽  
Computational Study ◽  
Cyano Group ◽  
Cycloaddition Reactions ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Reaction Channels ◽  
One Step ◽  
Step Mechanism

The regiochemistry of [3+2] cycloaddition (32CA) processes between benzonitrile N-oxide 1 and β-phosphorylated analogues of nitroethenes 2a–c has been studied using the Density Functional Theory (DFT) at the M062X/6-31+G(d) theory level. The obtained results of reactivity indices show that benzonitrile N-oxide 1 can be classified both as a moderate electrophile and moderate nucleophile, while β-phosphorylated analogues of nitroethenes 2a–c can be classified as strong electrophiles and marginal nucleophiles. Moreover, the analysis of CDFT shows that for [3+2] cycloadditions with the participation of β-phosphorylatednitroethene 2a and β-phosphorylated α-cyanonitroethene 2b, the more favored reaction path forms 4-nitro-substituted Δ2-isoxazolines 3a–b, while for a reaction with β-phosphorylated β-cyanonitroethene 2c, the more favored path forms 5-nitro-substituted Δ2-isoxazoline 4c. This is due to the presence of a cyano group in the alkene. The CDFT study correlates well with the analysis of the kinetic description of the considered reaction channels. Moreover, DFT calculations have proven the clearly polar nature of all analyzed [3+2] cycloaddition reactions according to the polar one-step mechanism.

scholarly journals Theoretical Study of Thermal Cracking For Acenaphthylene Molecule

2013 ◽  
Vol 10 (3) ◽  
pp. 1071-1081
Author(s):  
Baghdad Science Journal
Keyword(s):  
Density Functional ◽  
Theoretical Study ◽  
Reaction Path ◽  
Polyaromatic Hydrocarbons ◽  
Thermal Cracking ◽  
Triplet States ◽  
Bond Energies ◽  
Functional Theory ◽  
Repulsion Energy ◽  
Bond Breakage

Density Functional Theory (DFT) calculations were carried out to study the thermal cracking for acenaphthylene molecule to estimate the bond energies for breaking C8b-C5a , C5a-C5 , C5-C4 , and C5-H5 bonds as well as the activation energies. It was found that for C8b-C5a , C5-C4 , and C5-H5 reactions it is often possible to identify one pathway for bond breakage through the singlet or triplet states. The atomic charges , dipole moment and nuclear – nuclear repulsion energy supported the breakage bond .Also, it was found that the activation energy value for C5-H5 bond breakage is lower than that required for C8b-C5a , C5a-C5 , C5-C4 bonds which refer to C5-H5 bond in acenaphthylene molecule are weaker than C8b-C5a , C5a-C5 , C5-C4 bonds .It is reasonable to presume that C5-H5 bonds are broken first when a acenaphthylene molecule is exposed to thermal cracking. It seems that the characteristic planarity for the polyaromatic hydrocarbons is an important factor to acquire the molecule structure of the required stability along the reaction path . The trends in the bond energies and the configuration structures are discussed .

scholarly journals Selective Hydrogenation of Acetylene Catalysed by a B12N12 Cluster Doped with a Single Nickel Atom: A DFT Study

Catalysts ◽  
2020 ◽  
Vol 10 (1) ◽  
pp. 115 ◽  
Author(s):  
Yun Wang ◽  
Lihua Kang
Keyword(s):  
Selective Hydrogenation ◽  
Density Functional ◽  
Reaction Path ◽  
Nickel Atom ◽  
Single Atom ◽  
Functional Theory ◽  
Acetylene Hydrogenation ◽  
Selective Hydrogenation Of Acetylene ◽  
New Type ◽  
Catalytic Performances

To obtain a catalyst based on a non-precious metal that can replace traditional palladium-based selective catalysts of acetylene hydrogenation, the catalytic performances of two different configurations of a B12N12 cluster doped with a single nickel atom were studied by a density functional theory computational approach. After analysing the effect that the adsorption of reactants onto the clusters has on the reaction path, we determined the lowest energy path for the acetylene double hydrogenation. Comparing the acetylene hydrogenation activities and ethylene product selectivities of the B11N12Ni and B12N11Ni clusters, which have different doping sites, we determined the activities of these two catalysts to be similar to each other; however, the B11N12Ni cluster was calculated to have higher selectivity for ethylene as a product. This difference may be related to the moderate adsorption of hydrogen and acetylene on the B11N12Ni cluster. As a new type of nickel-based single-atom catalyst, B11N12Ni clusters may have research value in the selective hydrogenation of acetylene.

scholarly journals Theoretical Investigation of Energetic Salts with Pentazolate Anion

Molecules ◽  
2020 ◽  
Vol 25 (8) ◽  
pp. 1783
Author(s):  
Hao-Ran Wang ◽  
Chong Zhang ◽  
Bing-Cheng Hu ◽  
Xue-Hai Ju
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Functional Theory ◽  
Calculated Density ◽  
The Density Functional Theory ◽  
Energetic Salts ◽  
Vertical Electron Affinity ◽  
The Difference ◽  
Nitrogen Contents ◽  
Experimental Density

Energetic salts based on pentazolate anion (cyclo-N5−) have attracted much attention due to their high nitrogen contents. However, it is an enormous challenge to efficiently screen out an appropriate cation that can match well with cyclo-N5−. The vertical electron affinity (VEA) of the cations and vertical ionization potential (VIP) of the anions for 135 energetic salts and some cyclo-N5− salts were calculated by the density functional theory (DFT). The magnitudes of VEA and VIP, and their matchability were analyzed. The results based on the calculations at the B3LYP/6-311++G(d,p) and B3LYP/aug-cc-pVTZ levels indicate that there is an excellent compatibility between cyclo-N5− and cation when the difference between the VEA of cation and the VIP of cyclo-N5− anion is −2.8 to −1.0 eV. The densities of the salts were predicted by the DFT method. Relationship between the calculated density and the experimental density was established as ρExpt = 1.111ρcal − 0.06067 with a correlation coefficient of 0.905. This regression equation could be in turn used to calibrate the calculated density of the cyclo-N5− energetic salts accurately. This work provides a favorable way to explore the energetic salts with excellent performance based on cyclo-N5−.

TIME-DEPENDENT DENSITY FUNCTIONAL STUDY OF MULTIELECTRON TRANSFER IN Cq+–Na4 COLLISIONS

2010 ◽  
Vol 24 (24) ◽  
pp. 4811-4820
Author(s):  
Y. P. ZHANG ◽  
F. S. ZHANG ◽  
Y. GAO ◽  
H. W. CHANG ◽  
G. Q. XIAO
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Local Density ◽  
Time Dependent ◽  
Functional Study ◽  
Density Approximation ◽  
Functional Theory ◽  
The Difference ◽  
Multielectron Transfer ◽  
Dependent Density

The process of multielectron transfer from a Na 4 cluster induced by highly charged C 6+, C 4+, C 2+ and C + ions is studied using the method of time-dependent density functional theory within the local density approximation combined with the use of pseudopotential. The evolution of dipole moment changes and emitted electrons in Na 4 is obtained and the time-dependent probabilities with various charges are deduced. It is shown that the Na 4 cluster is strongly ionized by C 6+ and that the number of emitted electrons per atom of Na 4 is larger than that of Na 2 under the same condition. One can find that the detailed information of the emitted electrons from Na 4 is different from the same from Na 2, which is possibly related to the difference in structure between the two clusters.

Oxides, Silicides, and Silicates of Zirconium and Hafnium; Density Functional Theory Study

2002 ◽  
Vol 716 ◽  
Author(s):  
Maciej Gutowski ◽  
John E. Jaffe ◽  
Chun-Li Liu ◽  
Matt Stoker ◽  
Anatoli Korkin
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Gate Dielectric ◽  
Density Functional Theory Calculations ◽  
Heat Of Formation ◽  
Density Functional Theory Study ◽  
Functional Theory ◽  
Exchange Correlation ◽  
The Difference ◽  
Constituent Elements

AbstractIt is known that the chemistries of hafnium and zirconium are more nearly identical than for any other two congeneric elements. Thus, both zirconia and hafnia, with the dielectric constant K > 20, have emerged as potential replacements for silica (K = 3.9) as a gate dielectric. We report an important difference between the zirconia/Si and hafnia/Si interfaces based on density functional theory calculations with the Perdew-Wang 91 exchange-correlation functional on the oxides, silicides, and silicates of Zr and Hf. The zirconia/Si interface has been found to be unstable with respect to formation of silicides whereas the hafnia/Si interface is stable. The difference between the two interfaces results from the fact that HfO2 is more stable than ZrO2 (i.e. has a larger heat of formation from its constituent elements) by more than 53 kJ/mol. The hafnium silicides, on the other hand, are less stable than zirconium silicides by ca. 20 kJ/mol.

Calculation of electronic structure and mechanical properties of DO3–Fe75-xSi25Nix intermetallic compounds by first principles

2015 ◽  
Vol 29 (13) ◽  
pp. 1550087
Author(s):  
R. Ma ◽  
M. P. Wan ◽  
J. Huang ◽  
Q. Xie
Keyword(s):  
Mechanical Properties ◽  
Intermetallic Compounds ◽  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Elastic Parameters ◽  
Functional Theory ◽  
Ni Content ◽  
The Density Functional Theory ◽  
The Difference

Based on the density functional theory (DFT), the plane-wave pseudopotential method was used to investigate the electronic structures and mechanical properties of DO 3– Fe 75-x Si 25 Ni x(x = 0, 3.125, 6.25 and 9.375) intermetallic compounds. The elastic parameters were calculated, and then the bulk modulus, shear modulus and elastic modulus were derived. The paper then focuses on the discussion of ductility and plasticity. The results show that by adding appropriate Ni to Fe 3 Si intermetallic compound can improve the ductility. But the hardness will increase when the Ni content exceeds 6.25%. Analysis of density of states (DOS) and overlap populations indicates that with the difference of the strength of bonding and activity, there were some differences of ductility among different Ni contents. The Fe 71.875 Ni 3.125 Si 25 has the lowest hardness because the covalent bonding (Fe–Si bond and Si–Ni bond) has the minimum covalent electrons.

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