Irradiation-induced ordering in Pt-Cu alloy focusing on Pt7Cu

2015 ◽  
Vol 1760 ◽  
Author(s):  
T. Nagase ◽  
Y. Seno ◽  
H. Yasuda ◽  
H. Mori
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Alloy System ◽  
Functional Theory ◽  
High Voltage Electron Microscopy ◽  
Voltage Electron ◽  
Cu Alloy ◽  
Gcmc Simulation ◽  
Phase Intermetallic ◽  
Short Time

ABSTRACTThe existence of Pt7Cu ordering phase (intermetallic compound) was investigated by ab initio calculations and high voltage electron microscopy (HVEM) focusing on irradiation-induced ordering. The Pt7Cu ordering phase (cF32, prototype Ca7Ge) was predicted at 0 K through density functional theory (DFT), and using cluster expansion (CE) method and grand canonical Monte Carlo (GCMC) simulation, the ordering temperature of fcc-based Pt7Cu ordering phase was estimated to be above room temperature. The formation of Pt7Cu ordering phase was confirmed by a short-time irradiation for 3.6×103 s at 600 K. MeV electron irradiation can reduce drastically the annealing time for the ordering in the Pt-Cu alloy system, indicating that the combination of the prediction by ab initio calculations and HVEM can offer the unique opportunity to investigate the existence of ordering phase in alloys.

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.

Ab Initio Calculation of Mechanical Properties of Stacking Fault in 3C-SiC: Effect of Stress and Doping

2012 ◽  
Vol 717-720 ◽  
pp. 415-418
Author(s):  
Yoshitaka Umeno ◽  
Kuniaki Yagi ◽  
Hiroyuki Nagasawa
Keyword(s):  
Mechanical Properties ◽  
Ab Initio ◽  
Density Functional ◽  
Stacking Faults ◽  
Single Layer ◽  
Local Strain ◽  
Density Functional Theory Calculations ◽  
Stacking Fault ◽  
Functional Theory ◽  
N Doping

We carry out ab initio density functional theory calculations to investigate the fundamental mechanical properties of stacking faults in 3C-SiC, including the effect of stress and doping atoms (substitution of C by N or Si). Stress induced by stacking fault (SF) formation is quantitatively evaluated. Extrinsic SFs containing double and triple SiC layers are found to be slightly more stable than the single-layer extrinsic SF, supporting experimental observation. Effect of tensile or compressive stress on SF energies is found to be marginal. Neglecting the effect of local strain induced by doping, N doping around an SF obviously increase the SF formation energy, while SFs seem to be easily formed in Si-rich SiC.

scholarly journals Density Functional Theory and Complete Basis Set Ab Initio Computational Study of Five-, Six-, Seven- and Eight-hydrogen Coordinated Carbon Cations

1999 ◽  
Vol 23 (8) ◽  
pp. 502-503
Author(s):  
Branko S. Jursic
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Computational Study ◽  
Basis Set ◽  
Functional Theory ◽  
Complete Basis ◽  
Complete Basis Set ◽  
High Level

High level ab initio and density functional theory studies are performed on highly protonated methane species.

scholarly journals Ab initio molecular dynamics of hydrogen on tungsten surfaces

2021 ◽  
Author(s):  
Alberto Rodríguez-Fernández ◽  
Laurent Bonnet ◽  
Pascal Larrégaray ◽  
Ricardo Díez Muiño
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Ab Initio ◽  
Density Functional ◽  
Ab Initio Molecular Dynamics ◽  
Dissociation Process ◽  
Functional Theory ◽  
Classical Molecular Dynamics ◽  
Hydrogen Molecules

The dissociation process of hydrogen molecules on W(110) was studied using density functional theory and classical molecular dynamics.

Flexoelectricity in atomic monolayers from first principles

Nanoscale ◽  
2020 ◽  
Author(s):  
Shashikant Kumar ◽  
David Codony ◽  
Irene Arias ◽  
Phanish Suryanarayana
Keyword(s):  
Density Functional Theory ◽  
Transition Metal ◽  
Ab Initio ◽  
First Principles ◽  
Density Functional ◽  
Transition Metal Dichalcogenides ◽  
Functional Theory ◽  
Group Iii ◽  
Flexoelectric Effect ◽  
Metal Dichalcogenides

We study the flexoelectric effect in fifty-four select atomic monolayers using ab initio Density Functional Theory (DFT). Specifically, considering representative materials from each of Group III monochalcogenides, transition metal dichalcogenides...

Polaronic and Bipolaronic Enhancement of Second Hyperpolarizabilities in Dithienyl Polyenes from Ab Initio Quantum Methods

1999 ◽  
Vol 597 ◽  
Author(s):  
Steven Trohalaki ◽  
Robert J. Zellmer ◽  
Ruth Pachter
Keyword(s):  
Ab Initio ◽  
Density Functional ◽  
Valence Bond ◽  
Closed Shell ◽  
Functional Theory ◽  
Molecular Conformations ◽  
Hartree Fock ◽  
Molecular Charge ◽  
Field Methodology ◽  
Moller Plesset

AbstractSpangler and He [1,2] have shown that dithienyl polyenes form extremely stable bipolaronic dications when oxidatively doped in solution. Previous theoretical studies applied empirical methods to predict bipolaronic enhancement of hyperpolarizabilities for simple polyenes [3,4]. Here, we employ density functional theory to optimize the gas-phase molecular conformations of neutral, cationic, and dicationic forms of a series of dithienyl polyenes, where the number of ethene units, N, is varied from 1–5. Ab initio Hartree-Fock, generalized valence bond, configuration interaction, and Møller-Plesset calculations demonstrate that the dications are farily well described with a closed shell and therefore have little biradicaloid character. Second hyperpolarizabilities, γ, are subsequently calculated using ab initio Hartree-Fock theory and a finite field methodology. As expected, γ increases with the number of ethene units for a given molecular charge. The cations also show the largest increase in γ with N. For a given value of N, the cations display the largest γ values. However, if we treat the dication as a triplet, which might be present in solution, then it displays the largest γ.

Germanene: a new electronic gas sensing material

RSC Advances ◽  
2016 ◽  
Vol 6 (104) ◽  
pp. 102264-102271 ◽  
Author(s):  
Sanjeev K. Gupta ◽  
Deobrat Singh ◽  
Kaptansinh Rajput ◽  
Yogesh Sonvane
Keyword(s):  
Density Functional Theory ◽  
Ab Initio ◽  
Electronic Properties ◽  
Structural Stability ◽  
Density Functional ◽  
Gas Sensing ◽  
Functional Theory ◽  
Adsorption Characteristics ◽  
Sensing Material ◽  
Gas Molecules

The structural stability and electronic properties of the adsorption characteristics of several toxic gas molecules (NH3, SO2 and NO2) on a germanene monolayer were investigated using density functional theory (DFT) based on an ab initio method.

Electronic Structure Of (AgSb)xPbn-2xTen

2003 ◽  
Vol 793 ◽  
Author(s):  
Daniel I Bilc ◽  
S.D. Mahanti ◽  
M.G. Kanatzidis
Keyword(s):  
Electronic Structure ◽  
Ab Initio ◽  
Density Functional ◽  
Full Potential ◽  
Generalized Gradient ◽  
Two Component System ◽  
Functional Theory ◽  
Covalent Interaction ◽  
Salt Structure ◽  
Linearized Augmented Plane Wave

ABSTRACTComplex quaternary chalcogenides (AgSb)xPbn-2xTen (0<x<n/2) are thought to be narrow band-gap semiconductors which are very good candidates for room and high temperature thermoelectric applications. These systems form in the rock-salt structure similar to the well known two component system PbTe (x=0). In these systems Ag and Sb occupy Pb sites randomly although there is some evidence of short-range order. To gain insights into the electronic structure of these compounds, we have performed electronic structure calculations in AgSbTe2 (x=n/2). These calculations were carried out within ab initio density functional theory (DFT) using full potential linearized augmented plane wave (LAPW) method. The generalized gradient approximation (GGA) was used to treat the exchange and correlation potential. Spinorbit interaction (SOI) was incorporated using a second variational procedure. Since it is difficult to treat disorder in ab initio calculations, we have used several ordered structures for AgSbTe2. All these structures show semimetallic behavior with a pseudogap near the Fermi energy. Te and Sb p orbitals, which are close in energy, hybridize rather strongly indicating a covalent interaction between Te and Sb atoms.

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