Muon Site Estimations by DFT Calculations in Metal and Insulating Systems

2015 ◽  
Vol 827 ◽  
pp. 347-354 ◽  
Author(s):  
Isao Watanabe ◽  
E. Suprayoga ◽  
N. Adam ◽  
S.S. Mohm-Tajudin ◽  
A.F. Rozlan ◽  
...  
Keyword(s):  
Density Functional ◽  
Positive Charge ◽  
Muon Spin ◽  
Potential Minimum ◽  
Functional Theory ◽  
Muon Facility ◽  
The Density Functional Theory ◽  
Calculation Results ◽  
Minimum Potential ◽  
Muon Spin Precession

A way to estimate muon sites in materials is reported. Since the muon has a positive charge, one easiest and conventional way to estimate muon positions is to calculate minimum potential positions. We applied our developed method to estimate those potential minimum positions to some systems which have been studied by mons at the RIKEN-RAL Muon Facility and showed well defined muon-spin precession behavior in magnetically ordered states. Tentative calculation results by using the density functional theory are reported.

The Crystal Structure of Dibromonitrotoluen (DBNT) C7Br2H5 NO2

2011 ◽  
Vol 324 ◽  
pp. 209-212
Author(s):  
Mohamed Larbi Medjroubi ◽  
Ouarda Brihi ◽  
Noudjoud Hamdouni ◽  
Ali Boudjada ◽  
Jean Meinnel
Keyword(s):  
Crystal Structure ◽  
Density Functional ◽  
Molecular Conformation ◽  
Dynamic Properties ◽  
X Ray Diffraction ◽  
Functional Theory ◽  
The Density Functional Theory ◽  
Calculation Results ◽  
Experimental Spectroscopy ◽  
Good Probe

The crystal structure of Dibromonitrotoluen (DBNT) obtained at the ambient temperature 293k from the X-ray diffraction crystallizes in the space group P-1 with 2 molecules by mesh. The crystal growth is made along the a axis. In parallel with this study, a theoretical calculation of molecular conformation from the density functional theory (DFT) carried out using the Gaussian03 chain program in the case of isolated molecule, led to results of Optimization very close to the experiment. The molecular conformation calculations were made from two different functional the B3LYP and MPW1PW91. The values of bond lengths obtained from the functional MPW1PW91 and base set 6-311G are very close to the experiment with a gap of 1.25% (2.14% for the B3LYP) while for bond angles, calculation results are better for functional B3LYP (Lan2DZ) 0.95% and 1.02% for MPW1PW91.In this work a study of internal modes of Dibromonitrotoluen (DBNT) is presented, while comparing the infrared spectroscopic experimental results and the DFT studies of the isolated molecule. This material is a good probe to test the model precision and the calculated methods used to interpret dynamic properties by experimental spectroscopy.

scholarly journals Study on syngas methanation mechanism over Ni4/MCM-41 catalyst based on density functional theory

2019 ◽  
Vol 44 (3) ◽  
pp. 222-233 ◽  
Author(s):  
Jiaying Zhang
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Density Functional Theory Method ◽  
Functional Theory ◽  
Rate Determining Step ◽  
The Density Functional Theory ◽  
Calculation Results ◽  
Direct Dissociation ◽  
Methanation Catalyst ◽  
Mcm 41

The density functional theory method is employed to systematically explore the mechanism of syngas methanation on the Ni4/MCM-41 catalyst surface. The calculation results show that the optimal pathway of CH4 formation is CO + H → CHO + H → CH2O + H → CH3O → CH3 + H → CH4 with the rate-determining step of CH3O direct dissociation. Because the activation energy for the direct dissociation of CH3O species is much lower than that for the CH3OH formation (198.6 vs 264.8 kJ mol−1), there is almost no by-product CH3OH that appeared in the products of the syngas methanation over the Ni4/MCM-41 catalyst. Compared with other conventional nickel-based methanation catalysts, Ni4/MCM-41 catalyst is an excellent methanation catalyst with high selectivity of CH4.

Phase Structures and Properties of Au-Pd-M (M=Zr, Mo, Y) System

2015 ◽  
Vol 816 ◽  
pp. 722-725
Author(s):  
Ming Xie ◽  
You Cai Yang ◽  
Ji Ming Zhang ◽  
Yong Tai Chen ◽  
Sai Bei Wang ◽  
...  
Keyword(s):  
First Principles ◽  
Electronic Structures ◽  
Density Functional ◽  
Solidification Rate ◽  
Potential Method ◽  
Functional Theory ◽  
Structures And Properties ◽  
The Density Functional Theory ◽  
Calculation Results ◽  
Pseudo Potential

A series of new alloys including Au-Pd-M (M=Zr, Mo, Y) were developed in this study. The physical properties, electrical properties parameters and thermodynamics database of the alloys were established. The phase structure and composition were analyzed. The calculation results were verified by experiments. The influence of solidification rate to microstructures, morphology and grain size of Au-Pd-M alloys were analyzed. A first-principles plane-wave pseudo-potential method based on the density functional theory was used to investigate the electronic structures, bonding characters and energetic stability of Au-Pd-M alloys, the calculating results indicated that Au-Pd-Mo formed more easily than Au-Pd-Zr and Au-Pd-Y, and the formed Au-Pd-Mo is more stable than Au-Pd-Zr and Au-Pd-Y.

First-Principle Study of Structural and Electronic Properties of Ti-Doped SnO2

2013 ◽  
Vol 634-638 ◽  
pp. 2545-2549 ◽  
Author(s):  
Jing Kai Yang ◽  
Hong Li Zhao ◽  
Yan Zhu ◽  
Li Ping Zhao ◽  
Jian Li
Keyword(s):  
Electronic Properties ◽  
Density Functional ◽  
First Principle ◽  
Generalized Gradient ◽  
Functional Theory ◽  
First Principle Calculations ◽  
Generalized Gradient Approximation ◽  
The Density Functional Theory ◽  
Structural And Electronic Properties ◽  
Calculation Results

The structural and electronic properties of Ti-doped SnO2with 6.25 at.% are investigated with the first principle calculations based on the density functional theory within the generalized gradient approximation. The calculation results indicate that the crystal structure of Sn0.9375Ti0.0625O2possesses a smaller volume; the bond length of Ti-O is shorter than that of Sn-O; the relative angle θ change value of Sn-O-Sn→Ti-O-Ti is about 1.07%. Ti-O bond possesses more covalent ingredient and stronger bond energy than Sn-O bond. After the replacement of one Ti atom, O atom bonded with Ti atom possessed fewer electrons, the ratio of charges possessed by Ti atom and O atom dose not agree with the stoichiometry of compound, create more holes at the top of VB of Sn0.9375Ti0.0625O2, and lead to the increase of the conductivity.

scholarly journals Theoretical Studies on The Mechanism of Pd2+-Catalyzed Regioselective C-H Alkylation of Indole With MesICH2CF3OTf

2021 ◽  
Author(s):  
Yao Shi ◽  
Hongsheng Ma ◽  
Jiaxuan Shao ◽  
chao deng
Keyword(s):  
Reaction Mechanism ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Activation Process ◽  
Acetate Anion ◽  
Functional Theory ◽  
Planar Configuration ◽  
Square Planar ◽  
The Density Functional Theory ◽  
Calculation Results

Abstract The reaction mechanism of Pd2+-catalyzed regioselective C–H alkylation of indole with MesICH2CF3OTf has been investigated by the density functional theory calculations. The reaction mechanism mainly contains four steps：C-H activation, oxidative addition, reductive elimination and ligands substitution. From our calculations, we find that the C-H activation step was realized by the acetate anion (-OAc) assisted CMD process and the transition state of C-H activation process is a square planar configuration. Moreover, the calculation results suggest that the regioselectivity of C-H bond alkylation of indole with MesICH2CF3OTf can be ascribed to the different stability of the CMD transition states in C-H activation step and different acidities of C-H bonds.

Structural Shifting and Electronic Properties of Stone-Wales Defect in Armchair Edge (5,5) Carbon Nanotube

2013 ◽  
Vol 772 ◽  
pp. 380-385 ◽  
Author(s):  
Supri Jadi ◽  
A. Setiadi
Keyword(s):  
Carbon Nanotube ◽  
Density Functional ◽  
Minimum Energy ◽  
Elastic Band ◽  
Functional Theory ◽  
Barrier Energy ◽  
Wales Defect ◽  
The Density Functional Theory ◽  
Calculation Results ◽  
Nudge Elastic Band

Stone Wales (SW) defect is one type of topological defect on the CNT, in this study we performed first principles calculations of SW defects in armchair edge (5,5) carbon nanotube (CNT) by the density functional theory (DFT). Two different defects were studied such as longitudinal and circumference types. Our calculation results show that a longitudinal SW defect is more stable than circumference SW defect. However barrier energy as parameter to control the SW defect in CNT was studied, in calculation we applied Nudge Elastic Band (NEB) method to find minimum energy path (MEP) and barrier energy for SW defect transitions. The result shows that barrier energy of circumference SW defect is lower than another one. We also found that in the case of circumference SW defect, armchair edge (5,5) CNT become semiconductor with the band gap of 0.0544 eV.

scholarly journals Electronic structure and effective masses of TlInSe2 under pressure

2018 ◽  
Vol 35 (4) ◽  
pp. 857-860 ◽  
Author(s):  
G.S. Orudzhev ◽  
N.A. Ismayilova ◽  
V.N. Jafarova
Keyword(s):  
Density Functional Theory ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional ◽  
Pressure Effect ◽  
Functional Theory ◽  
Effective Masses ◽  
Gap Closure ◽  
The Density Functional Theory ◽  
Calculation Results

Abstract We have studied the band structure and the band gap closure of TlInSe2 under pressure in the range of 0 GPa to 21 GPa, by employing the first-principles method based on the density functional theory. We discuss the possible metallic transition in the tetragonal phase of TlInSe2 crystal. Our calculation results show that the value of the pressure at the crossover from the direct to the indirect gap is found to be 8 GPa. The “semiconductor-metal” transition is determined to occur at 14 GPa. The study of the pressure effect on the effective masses for semiconductor state shows that with increasing pressure, the effective masses of holes and electrons decrease and the anisotropy of effective masses of holes is weakening.

scholarly journals Strain Investigation on Spin-Dependent Transport Properties of γ-Graphyne Nanoribbon Between Gold Electrodes

2021 ◽  
Vol 16 (1) ◽  
Author(s):  
Yun Li ◽  
Xiaobo Li ◽  
Shidong Zhang ◽  
Liemao Cao ◽  
Fangping Ouyang ◽  
...  
Keyword(s):  
Transport Properties ◽  
High Performance ◽  
Density Functional ◽  
Strain Engineering ◽  
Molecular Junctions ◽  
Spin Splitting ◽  
Functional Theory ◽  
Spin Dependent Transport ◽  
The Density Functional Theory ◽  
Dependent Transport

AbstractStrain engineering has become one of the effective methods to tune the electronic structures of materials, which can be introduced into the molecular junction to induce some unique physical effects. The various γ-graphyne nanoribbons (γ-GYNRs) embedded between gold (Au) electrodes with strain controlling have been designed, involving the calculation of the spin-dependent transport properties by employing the density functional theory. Our calculated results exhibit that the presence of strain has a great effect on transport properties of molecular junctions, which can obviously enhance the coupling between the γ-GYNR and Au electrodes. We find that the current flowing through the strained nanojunction is larger than that of the unstrained one. What is more, the length and strained shape of the γ-GYNR serves as the important factors which affect the transport properties of molecular junctions. Simultaneously, the phenomenon of spin-splitting occurs after introducing strain into nanojunction, implying that strain engineering may be a new means to regulate the electron spin. Our work can provide theoretical basis for designing of high performance graphyne-based devices in the future.

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