scholarly journals Bimetallic nanocatalysts PtCu and PtNi for fuel cells

2020 ◽  
Vol 21 (2) ◽  
pp. 211-214
Author(s):  
O. M. Chernikova ◽  
Y. V. Ogorodnik
Keyword(s):  
Density Functional ◽  
Bimetallic Catalyst ◽  
Theoretical Calculations ◽  
Catalyst Activity ◽  
Main Research ◽  
Heterogeneous Catalytic ◽  
Physical Mechanisms ◽  
Oxidation Of Methanol ◽  
The Density Functional Theory ◽  
Bimetallic Nanocatalysts

We review the physical mechanisms of heterogeneous catalytic oxidizing reactions methanol oxidation using bimetallic film layered mechanically strained PtNi and PtCu-based catalysts. The main research methods are theoretical calculations based on the density functional theory and the ˝ab initio˝ pseudopotential method. The work illustrates that the mechanical stress and the presence of dissociated oxygen have the greatest impact on increasing electron bimetallic catalyst activity during the oxidation of methanol with using bimetallic layered mechanically strained PtNi and PtCu-based catalysts. The compression of the platinum film pushes the electron density outside the film and it gives the density an elongated form and increases the chemical and absorption activity of the film.

scholarly journals Theoretical Calculations on the Mechanism of Enantioselective Copper(I)-Catalyzed Addition of Enynes to Ketones

Catalysts ◽  
2018 ◽  
Vol 8 (9) ◽  
pp. 359 ◽  
Author(s):  
Hanwei Li ◽  
Mingliang Luo ◽  
Guohong Tao ◽  
Song Qin
Keyword(s):  
Density Functional Theory ◽  
Steric Hindrance ◽  
Phenyl Ring ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Dft Method ◽  
Catalytic Cycle ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Chiral Systems

Computational investigations on the bisphospholanoethane (BPE)-ligated Cu-catalyzed enantioselective addition of enynes to ketones were performed with the density functional theory (DFT) method. Two BPE-mesitylcopper (CuMes) catalysts, BPE-CuMes and (S,S)-Ph-BPE–CuMes, were employed to probe the reaction mechanism with the emphasis on stereoselectivity. The calculations on the BPE-CuMes system indicate that the active metallized enyne intermediate acts as the catalyst for the catalytic cycle. The catalytic cycle involves two steps: (1) ketone addition to the alkene moiety of the metallized enyne; and (2) metallization of the enyne followed by the release of product with the recovery of the active metallized enyne intermediate. The first step accounts for the distribution of the products, and therefore is the stereo-controlling step in chiral systems. In the chiral (S,S)-Ph-BPE–CuMes system, the steric hindrance is vital for the distribution of products and responsible for the stereoselectivity of this reaction. The steric hindrance between the phenyl ring of the two substrates and groups at the chiral centers in the ligand skeleton is identified as the original of the stereoselectivity for the titled reaction.

First principle investigations of the optical properties of Zn1-xMgxS, Zn1-xMgxSe and Zn1-xMgxTe ternary alloys

2014 ◽  
Vol 28 (31) ◽  
pp. 1450221 ◽  
Author(s):  
M. Dadsetani ◽  
A. Zeinivand
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Random Phase ◽  
Ternary Alloys ◽  
Optical Absorption Coefficient ◽  
Full Potential ◽  
Generalized Gradient ◽  
The Density Functional Theory ◽  
Ternary Semiconductor

Optical properties of Zn 1-x Mg x S , Zn 1-x Mg x Se and Zn 1-x Mg x Te (0 ≤ x ≤ 1) ternary semiconductor alloys are calculated using the full potential linearized augmented plane wave within the density functional theory. The exchange correlation potential is treated by the generalized gradient approximation (GGA) within Perdew et al. scheme. The real and imaginary parts of the dielectric function ε(ω), the refractive index n(ω), the extinction coefficient k(ω), the optical absorption coefficient α(ω), the reflectivity R(ω) and the electron energy loss function (EELS) are calculated within random phase approximation (RPA). Our results are compared with the previous theoretical calculations and available experimental data. Moreover, the interband transitions responsible for the structures seen in the spectra are specified. It is shown that, the chalcogen p states as initial and Zn 4s, Mg 3s, chalcogen d states as final states perform the major role in optical transitions.

scholarly journals Optical Properties of DMA-π-DCV Derivatives: A Theoretical Inspection under the DFT Microscope

2016 ◽  
Vol 2016 ◽  
pp. 1-12 ◽  
Author(s):  
Joaquín Calbo
Keyword(s):  
Optical Properties ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Test System ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Donor Acceptor ◽  
Derivatives Of ◽  
Bridge Length ◽  
Theory Framework

The optical properties of a series of donor-acceptor N,N-dimethylaniline-π-dicyanovinylene (DMA-π-DCV) chromophores have been investigated under the density functional theory framework. Focus has been made on the low-lying charge-transfer (CT) electronic transitions for which experimental data is available. The effect of theπ-conjugated bridge length and type was analysed between the families of oligoene and oligoyne derivatives of increasing size. Theoretical calculations demonstrate that the ethylene bridge is a betterπ-communicator and allows for more delocalized frontier molecular orbitals compared to the acetylene spacer. TheΛdiagnostic test allowed rationalization of the orbital spatial overlap in the main CT excitations. The performance of different density functional rungs was assessed in the prediction of the lowest-lying CT electronic transition. Surprisingly, most modern long-range corrected functionals demonstrated to provide among the largest errors, whereas hybrid functionals showed the best performance. Solvatochromism was confirmed in both oligoene and oligoyne compounds. A donor-acceptor-donor triad based on tetrathiafulvalene was utilised as a test system for the prediction of its two CT bands of different nature, energy, and intensity. The hybrid PBE0 (or a similar hybrid analogue) consolidates as the best choice for the prediction of CT excitations in the DMA-π-DCV push-pull family.

A theoretical investigation on promising acceptor groups for POM-based dyes: from electronic structure to photovoltaic conversion efficiency

2020 ◽  
Vol 8 (1) ◽  
pp. 219-227 ◽  
Author(s):  
Yu Gao ◽  
Wei Guan ◽  
Li-Kai Yan ◽  
Zhong-Min Su
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Time Dependent ◽  
Functional Theory ◽  
Photovoltaic Conversion Efficiency ◽  
Acceptor Group ◽  
The Density Functional Theory ◽  
Td Dft

Theoretical calculations based on the density functional theory (DFT) and time-dependent DFT (TD-DFT) were employed to screen efficient acceptor group candidates for POM-based dyes.

Theoretical calculations of stability, mechanical and thermodynamic properties of IVA group Willemite-II nitrides

2015 ◽  
Vol 14 (04) ◽  
pp. 1550024 ◽  
Author(s):  
Ying-Chun Ding ◽  
Min Chen ◽  
Wen-Juan Wu
Keyword(s):  
Experimental Data ◽  
Thermodynamic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Mechanical Anisotropy ◽  
First Principles Calculations ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Good Agreement

The structural stability and mechanical and thermodynamic properties of WII- A 3 N 4 ( A=C , Si , Ge and Sn ) are calculated by first-principles calculations based on the density functional theory. The calculated lattice parameters and elastic constants of WII- A 3 N 4 ( A=C , Si , Ge and Sn ) are in good agreement with the experimental data and previously calculated values. WII- A 3 N 4 ( A=C , Si , Ge and Sn ) compounds are also found to be thermodynamically and mechanically stable. The results suggest that hardness of WII- C 3 N 4 is the hardest of these C 3 N 4 polymorphs. The hardness of WII- Sn 3 N 4 is the smallest among WII- A 3 N 4 ( A=C , Si , Ge and Sn ). Furthermore, the mechanical anisotropy, Debye temperature, the minimum thermal conductivity and thermodynamic properties of WII- A 3 N 4 ( A=C , Si , Ge and Sn ) compounds can be investigated.

scholarly journals Theoretical Calculations of Structural, Mechanical, Electronic And Optical Properties of Sn2S3 Under Pressure

2021 ◽  
Author(s):  
Baishu Chen ◽  
Wenxia Zhu ◽  
Chunxiang Wang ◽  
Chang Wang ◽  
Yuanzuo Li ◽  
...  
Keyword(s):  
Optical Properties ◽  
Band Gap ◽  
Density Functional ◽  
Mechanical Stability ◽  
Pressure Effect ◽  
Theoretical Calculations ◽  
Structural Parameters ◽  
Electronic And Optical Properties ◽  
Lattice Constants ◽  
The Density Functional Theory

Abstract The pressure effect on the structural, mechanical, electronic and optical properties of Sn2S3 in the pressure range of 0–35 GPa have been evaluated by means of the first-principles calculations based on the density-functional theory. The structural parameters of Sn2S3 at 0 GPa such as lattice constants and cell volumes are consistent with the previous theoretical and experiment reports. The mechanical properties about the elastic constants (Cij) and polycrystalline elastic modulus (B, G and E) under pressure are calculated for the first time. Furthermore, the results suggest that the Sn2S3 is predicted to be mechanically stable in the range of pressure from 0 to 35 GPa in the light of the mechanical stability conditions. The Sn2S3 is found to be ductile from the value of B/G. With the increasing of pressure, the ductility of Sn2S3 enhances monotonously. The pressure effect on the energy band gap and density of states of Sn2S3 is also discussed, which indicates that the pressure makes the band gap of Sn2S3 decreased. The optical properties of Sn2S3 are calculated in the range 0–35 eV, and the results show that the Sn2S3 under pressure has stronger visible light absorption in comparison with 0 GPa.

scholarly journals Efficient nickel-based catalysts for amine regeneration of CO2 capture: From experimental to calculations verifications

2021 ◽  
Author(s):  
Qiang Sun ◽  
Yu Mao ◽  
Hongxia Gao ◽  
Teerawat Sema ◽  
Sen Liu ◽  
...  
Keyword(s):  
Catalytic Activity ◽  
Co2 Capture ◽  
Density Functional ◽  
Catalytic Mechanism ◽  
Theoretical Calculations ◽  
High Heat ◽  
Catalytic Performance ◽  
Industrial Applications ◽  
Co2 Desorption ◽  
The Density Functional Theory

High heat duty is an urgent challenge for industrial applications of amine-based CO2 capture. In this work, we report a novel, stable, efficient, and inexpensive Ni-HZSM-5 catalyst to reduce the heat duty. The density functional theory (DFT) calculations successfully explain the catalytic performance. The catalytic activity associates with the combined properties of MSA × B/L × Ni2+. The 7.85-Ni-HZ catalyst presents an excellent catalytic activity for the CO2 desorption: it increases the amount of desorbed CO2 up to 36%, reduces the heat duty by 27.07% compared with the blank run, and possesses high stability during five cyclic tests. A possible catalytic mechanism for the Ni-HZSM-5 catalysts through assisting carbamate breakdown and promoting CO2 desorption is proposed based on experimental results and theoretical calculations. Therefore, the results present that the 7.85-Ni-HZ catalyst significantly accelerates the protons transfer in CO2 desorption and can potentially apply in industrial CO2 capture.

scholarly journals Optimization and Computational Approach to Understand the Adsorption Behavior of Alizarine Red S on the Surface of Fish Scales

2021 ◽  
Vol 11 (6) ◽  
pp. 14918-14934
Keyword(s):  
Density Functional ◽  
Theoretical Calculations ◽  
Fish Scales ◽  
Functional Theory ◽  
Normal Probability ◽  
The Density Functional Theory ◽  
Metropolis Monte Carlo ◽  
Dyes Adsorption ◽  
Factorial Design Analysis ◽  
Natural Composite

The key components of fish scales are hydroxyapatite and collagen, which form a natural composite. In this present study, fish scales were used as biosorbent to uptake Alizarine Red S dyes from the wastewaters. Here, dye concentration, adsorbent amount, pH, and temperature were optimized using complete factorial design analysis. Sixteen experiments were required, and a linear mathematical model representing the influence of the different variables and their interactions was obtained. The discussion covered analysis of variance (ANOVA), normal probability plots of residuals, and surface plots. Theoretical calculations by Metropolis Monte Carlo (MC) methods, the density functional theory (DFT), and the electrostatic potential surface (ESP) analysis were achieved to obtain a more understanding of the dyes adsorption mechanism on both collagen and hydroxyapatite (HDA) surfaces. The findings results exhibited that the ARS dye presents more tendency of adsorption on the collagen than on the HDA surface.

F2 storage by confinement inside carbon nanotubes

2016 ◽  
Vol 94 (1) ◽  
pp. 15-19 ◽  
Author(s):  
Wiem Felah Gtari ◽  
Bahoueddine Tangour
Keyword(s):  
Carbon Nanotubes ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Density Functional Theory Method ◽  
Van Der Waals Interactions ◽  
Basis Set ◽  
Basis Sets ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Walled Carbon Nanotubes

Theoretical calculations have been achieved to study the interaction between the confined F2 molecule along the nanotube axis and perpendicular to it and armchair (n,n) single-walled carbon nanotubes with n = 4, 5, 6, 7, and 8 and the zig-ag nanotube (9,0) using the density functional theory method with the CAM-B3LYP functional and both cc-pVQZ and STO-3G basis sets. The interaction of the F2 molecule with the nanotube is different according to the molecular orientation, the chirality of the carbon nanotube, and the confinement space extension. These results interpreted by means of van der Waals interactions reveal anisotropic and competitive behavior at the nanometric level. The π electrons of the nanotube interact with the lone pairs of F2 highlighting its lateral polarizability. The encapsulated F2 molecule is stable along and perpendicular to the nanotube (5,5) and (6,6) axis. The best stabilization energy is obtained fornanotube (5,5) at the perpendicular position using the cc-pVQZ basis set.

Phase Transition and Elastic Properties of Zinc Sulfide Under High Pressure from First Principles Calculations

2011 ◽  
Vol 66 (10-11) ◽  
pp. 656-660
Author(s):  
Dai Wei ◽  
Song Jin-Fan ◽  
Wang Ping ◽  
Lu Cheng ◽  
Lu Zhi-Wen ◽  
...  
Keyword(s):  
Phase Transition ◽  
High Pressure ◽  
Zinc Sulfide ◽  
Elastic Properties ◽  
First Principles ◽  
Density Functional ◽  
Theoretical Calculations ◽  
Structural Phase ◽  
Functional Theory ◽  
The Density Functional Theory

A theoretical investigation on structural and elastic properties of zinc sulfide semiconductor under high pressure is performed by employing the first-principles method based on the density functional theory. The calculated results show that the transition pressure Pt for the structural phase transition from the B3 structure to the B1 structure is 17:04 GPa. The calculated values are generally speaking in good agreement with experiments and with similar theoretical calculations.

Sign in / Sign up

Export Citation Format

Share Document