scholarly journals Anisotropic optical response of gold-silver alloys

2021 ◽  
Author(s):  
Hiago Maurilio Lopes Carvalho ◽  
Mariama Rebello Sousa Dias ◽  
Anibal Thiago Bezerra
Keyword(s):  
Density Functional ◽  
Optical Response ◽  
Functional Theory ◽  
Silver Alloys ◽  
Optical Responses ◽  
Independent Particle ◽  
Gold Silver ◽  
Experimental Works ◽  
Principle Density Functional Theory ◽  
D Orbitals

Abstract Gold and silver alloys enable novel opportunities for engineering materials with distinct optical responses. Here we investigate the optical properties of gold and silver (Ag x Au 1−x) structures using First-Principle Density Functional Theory (DFT) for gold concentrations varying from 0% up to 100% with steps of 25%. Results of the optical permittivity are analyzed with the independent particle approximation and compared with previously reported theoretical and experimental works. The pure systems and the ones with unbalanced concentrations exhibit isotropic optical responses. The Ag 0.50 Au 0.50 shows an anisotropic response among the y-direction and the xz-direction, mainly in the intraband transition energy range. The anisotropy is elucidated in terms of the d-orbitals density of states and the charge distribution with the structure. The anisotropic optical response can be the origin of the discrepancies among reported experimental results for structures with the same stoichiometry.

scholarly journals Boron-Decorated Pillared Graphene as the Basic Element for Supercapacitors: An Ab Initio Study

2021 ◽  
Vol 11 (8) ◽  
pp. 3496
Author(s):  
Dmitry A. Kolosov ◽  
Olga E. Glukhova
Keyword(s):  
Density Functional ◽  
Dft Method ◽  
Heat Of Formation ◽  
Basic Element ◽  
Supercapacitor Electrode ◽  
Functional Theory ◽  
Icosahedral Clusters ◽  
New Material ◽  
Principle Density Functional Theory ◽  
Specific Quantum

In this work, using the first-principle density functional theory (DFT) method, we study the properties of a new material based on pillared graphene and the icosahedral clusters of boron B12 as a supercapacitor electrode material. The new composite material demonstrates a high specific quantum capacitance, specific charge density, and a negative value of heat of formation, which indicates its efficiency. It is shown that the density of electronic states increases during the addition of clusters, which predictably leads to an increase in the electrode conductivity. We predict that the use of a composite based on pillared graphene and boron will increase the efficiency of existing supercapacitors.

scholarly journals Ab Initio Study of Ferroelectric Critical Size of SnTe Low-Dimensional Nanostructures

Nanomaterials ◽  
2020 ◽  
Vol 10 (4) ◽  
pp. 732 ◽  
Author(s):  
Takahiro Shimada ◽  
Koichiro Minaguro ◽  
Tao Xu ◽  
Jie Wang ◽  
Takayuki Kitamura
Keyword(s):  
Density Functional ◽  
Critical Size ◽  
Density Functional Theory Calculations ◽  
Cell Width ◽  
Functional Theory ◽  
Unit Cells ◽  
Principle Density Functional Theory ◽  
Low Dimensional ◽  
Insight Into ◽  
Ferroelectric Perovskite

Beyond a ferroelectric critical thickness of several nanometers existed in conventional ferroelectric perovskite oxides, ferroelectricity in ultimately thin dimensions was recently discovered in SnTe monolayers. This discovery suggests the possibility that SnTe can sustain ferroelectricity during further low-dimensional miniaturization. Here, we investigate a ferroelectric critical size of low-dimensional SnTe nanostructures such as nanoribbons (1D) and nanoflakes (0D) using first-principle density-functional theory calculations. We demonstrate that the smallest (one-unit-cell width) SnTe nanoribbon can sustain ferroelectricity and there is no ferroelectric critical size in the SnTe nanoribbons. On the other hand, the SnTe nanoflakes form a vortex of polarization and lose their toroidal ferroelectricity below the surface area of 4 × 4 unit cells (about 25 Å on one side). We also reveal the atomic and electronic mechanism of the absence or presence of critical size in SnTe low-dimensional nanostructures. Our result provides an insight into intrinsic ferroelectric critical size for low-dimensional chalcogenide layered materials.

Structural, Elastic and Electronic Properties of γ˝ Phase Precipitate in Mg-Gd-Zn Alloy

2019 ◽  
Vol 41 (6) ◽  
pp. 932-932
Author(s):  
Mengmeng Wu Mengmeng Wu ◽  
Rongkai Pan Rongkai Pan ◽  
Jilei Liang Jilei Liang ◽  
Guohai Zhou Guohai Zhou ◽  
Li Ma and Chunyu Zhang Li Ma and Chunyu Zhang
Keyword(s):  
Density Functional ◽  
Elastic Anisotropy ◽  
Poisson Ratio ◽  
Covalent Bond ◽  
Generalized Gradient ◽  
Electronic Density ◽  
Functional Theory ◽  
Full Relaxation ◽  
Principle Density Functional Theory ◽  
Zn Alloy

The γ˝ phase (Mg4GdZn) precipitate in Mg-Gd-Zn alloy was calculated via first-principle density functional theory within the generalized gradient approximation. Through structure optimization of full relaxation, the lattice parameters were theoretically obtained, and the calculated Mg4GdZn is the most energetically stable in view of the formation energy. Independent elastic constants were also calculated, illustrating the calculated Mg4GdZn is mechanically stable. The shear modulus, polycrystalline bulk modulus, Poisson ratio, and Young’s modulus of Mg4GdZn were calculated via the Voigt-Reuss-Hill approximation. Elastic anisotropy and ductility were analyzed in details. Seen from their charge density distribution and electronic density of states, both metallic bond and covalent bond were found in Mg4GdZn.

Density functional theory study of the stability of the tetrabutylphosphonium and tetrabutylammonium montmorillonites

Clay Minerals ◽  
2019 ◽  
Vol 54 (1) ◽  
pp. 41-48 ◽  
Author(s):  
Eva Scholtzová ◽  
Daniel Tunega
Keyword(s):  
Density Functional Theory ◽  
Hydrogen Bonds ◽  
Density Functional ◽  
Dynamic Properties ◽  
Organic Cations ◽  
Structure Stability ◽  
Functional Theory ◽  
Interatomic Distances ◽  
Principle Density Functional Theory ◽  
The Stability

AbstractThe stability of organoclays prepared from smectites and organic cations depends on the type of used cation, among other factors. This study provides a prediction of the structure, stability and dynamic properties of organoclays based on montmorillonite (Mt) intercalated with two types of organic cations – tetrabutylammonium (TBA) and tetrabutylphosphonium (TBP) – using first-principle density functional theory. The results obtained from simulations were also used in the interpretation of the experimental infrared spectrum of the TBP-Mt organoclay. Analysis of interatomic distances showed that weak C–O···H hydrogen bonds were important in the stabilization of both TBA- and TBP-Mt models, with slightly stronger hydrogen bonds for the TBP cation. Calculated intercalation and adsorption reaction energies (ΔEint//ΔEads*/ΔEads**) confirmed that TBP-Mt structures (–72.4//–32.8/–53.8 kJ/mol) were considerably more stable than TBA-Mt structures (–56.7//–22.6/–37.4 kJ/mol). The stronger interactions of the alkyl chains of the TBP cation with Mt basal surfaces in comparison to those of the TBA cation were also correlated with the positions of the calculated bands of the C–H stretching vibrations.

The optical response of nanoclusters under confinement

RSC Advances ◽  
2015 ◽  
Vol 5 (94) ◽  
pp. 77478-77489 ◽  
Author(s):  
Balasaheb J. Nagare
Keyword(s):  
Density Functional Theory ◽  
Optical Properties ◽  
Density Functional ◽  
Optical Response ◽  
Real Space ◽  
Space Time ◽  
Time Dependent ◽  
Functional Theory ◽  
Dependent Density

We report the optical properties of metallic and semiconductor nanoclusters with various sizes as a function of confinement using real-space time dependent density functional theory (TDDFT).

A study on the electronic and interfacial structures of monolayer ReS2–metal contacts

2017 ◽  
Vol 19 (39) ◽  
pp. 27052-27058 ◽  
Author(s):  
Jin Wang ◽  
Guofeng Yang ◽  
Rui Sun ◽  
Pengfei Yan ◽  
Yanan Lu ◽  
...  
Keyword(s):  
First Principles ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
Nickel Titanium ◽  
Metal Contacts ◽  
Functional Theory ◽  
Interfacial Structures ◽  
Gold Silver ◽  
Rigorous Study ◽  
Top Contact

In this paper, we perform a systematic and rigorous study to evaluate the Ohmic nature of the top-contact formed by the monolayer ReS2(mReS2) and metals (gold, silver, platinum, nickel, titanium, and scandium) by means of first-principles density functional theory calculations.

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