scholarly journals Topological Anderson Insulator in Cation-Disordered Cu2ZnSnS4

Nanomaterials ◽  
2021 ◽  
Vol 11 (10) ◽  
pp. 2595
Author(s):  
Binayak Mukherjee ◽  
Eleonora Isotta ◽  
Carlo Fanciulli ◽  
Narges Ataollahi ◽  
Paolo Scardi
Keyword(s):  
Density Functional ◽  
Surface States ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Material System ◽  
Slab Geometry ◽  
Functional Theory ◽  
Cation Disorder ◽  
Real Material ◽  
Reactive Mechanical Alloying

We present the first candidate for the realization of a disorder-induced Topological Anderson Insulator in a real material system. High-energy reactive mechanical alloying produces a polymorph of Cu2ZnSnS4 with high cation disorder. Density functional theory calculations show an inverted ordering of bands at the Brillouin zone center for this polymorph, which is in contrast to its ordered phase. Adiabatic continuity arguments establish that this disordered Cu2ZnSnS4 can be connected to the closely related Cu2ZnSnSe4, which was previously predicted to be a 3D topological insulator, while band structure calculations with a slab geometry reveal the presence of robust surface states. This evidence makes a strong case in favor of a novel topological phase. As such, the study opens up a window to understanding and potentially exploiting topological behavior in a rich class of easily-synthesized multinary, disordered compounds.

scholarly journals The Stone–Wales transformation: from fullerenes to graphite, from radiation damage to heat capacity

2016 ◽  
Vol 374 (2076) ◽  
pp. 20150317 ◽  
Author(s):  
M. I. Heggie ◽  
G. L. Haffenden ◽  
C. D. Latham ◽  
T. Trevethan
Keyword(s):  
Heat Capacity ◽  
Density Functional ◽  
Local Density ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Functional Theory ◽  
High Temperature Heat Capacity ◽  
Bond Rotation ◽  
Buckminster Fullerene ◽  
Equilibrium Concentrations

The Stone–Wales (SW) transformation, or carbon-bond rotation, has been fundamental to understanding fullerene growth and stability, and ab initio calculations show it to be a high-energy process. The nature and topology of the fullerene energy landscape shows how the I h -C 60 must be the final product, if SW transformations are fast enough, and various mechanisms for their catalysis have been proposed. We review SW transformations in fullerenes and then discuss the analogous transformation in graphite, where they form the Dienes defect, originally posited to be a transition state in the direct exchange of a bonded atom pair. On the basis of density functional theory calculations in the local density approximation, we propose that non-equilibrium concentrations of the Dienes defect arising from displacing radiation are rapidly healed by point defects and that equilibrium concentrations of Dienes defects are responsible for the divergent ultra-high-temperature heat capacity of graphite. This article is part of the themed issue ‘Fullerenes: past, present and future, celebrating the 30th anniversary of Buckminster Fullerene’.

scholarly journals Gold surfaces and nanoparticles are protected by Au(0)–thiyl species and are destroyed when Au(I)–thiolates form

2016 ◽  
Vol 113 (11) ◽  
pp. E1424-E1433 ◽  
Author(s):  
Jeffrey R. Reimers ◽  
Michael J. Ford ◽  
Arnab Halder ◽  
Jens Ulstrup ◽  
Noel S. Hush
Keyword(s):  
Density Functional ◽  
Surface States ◽  
High Energy ◽  
Gold Surfaces ◽  
Simple Method ◽  
Functional Theory ◽  
Polarization Effects ◽  
Nanoparticle Growth ◽  
Thiolate Anion ◽  
C And N

The synthetic chemistry and spectroscopy of sulfur-protected gold surfaces and nanoparticles is analyzed, indicating that the electronic structure of the interface is Au(0)–thiyl, with Au(I)–thiolates identified as high-energy excited surface states. Density-functional theory indicates that it is the noble character of gold and nanoparticle surfaces that destabilizes Au(I)–thiolates. Bonding results from large van der Waals forces, influenced by covalent bonding induced through s–d hybridization and charge polarization effects that perturbatively mix in some Au(I)–thiolate character. A simple method for quantifying these contributions is presented, revealing that a driving force for nanoparticle growth is nobleization, minimizing Au(I)–thiolate involvement. Predictions that Brust–Schiffrin reactions involve thiolate anion intermediates are verified spectroscopically, establishing a key feature needed to understand nanoparticle growth. Mixing of preprepared Au(I) and thiolate reactants always produces Au(I)–thiolate thin films or compounds rather than monolayers. Smooth links to O, Se, Te, C, and N linker chemistry are established.

Hydrogen in tungsten: Absorption, diffusion, vacancy trapping, and decohesion

2010 ◽  
Vol 25 (2) ◽  
pp. 315-327 ◽  
Author(s):  
Donald F. Johnson ◽  
Emily A. Carter
Keyword(s):  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
Fusion Reactors ◽  
Adsorbed Hydrogen ◽  
Functional Theory ◽  
Outward Diffusion ◽  
Vacancy Trapping ◽  
High Energy Particles ◽  
Interaction Surface

Understanding the interaction between atomic hydrogen and solid tungsten is important for the development of fusion reactors in which proposed tungsten walls would be bombarded with high energy particles including hydrogen isotopes. Here, we report results from periodic density-functional theory calculations for three crucial aspects of this interaction: surface-to-subsurface diffusion of H into W, trapping of H at vacancies, and H-enhanced decohesion, with a view to assess the likely extent of hydrogen isotope incorporation into tungsten reactor walls. We find energy barriers of (at least) 2.08 eV and 1.77 eV for H uptake (inward diffusion) into W(001) and W(110) surfaces, respectively, along with very small barriers for the reverse process (outward diffusion). Although H dissolution in defect-free bulk W is predicted to be endothermic, vacancies in bulk W are predicted to exothermically trap multiple H atoms. Furthermore, adsorbed hydrogen is predicted to greatly stabilize W surfaces such that decohesion (fracture) may result from high local H concentrations.

scholarly journals Spin-Filtering Effects in Würtzite and Graphite-Like AlN Nanowires with Mn Impurities

2013 ◽  
Vol 2013 ◽  
pp. 1-5 ◽  
Author(s):  
G. A. Nemnes
Keyword(s):  
Phase Transition ◽  
Density Functional ◽  
Surface States ◽  
Density Functional Theory Calculations ◽  
Functional Theory ◽  
Group Iii ◽  
Magnetic Nanowire ◽  
Group Iii Nitride ◽  
Basic Prerequisite ◽  
Spin Filtering

Spin transport properties of magnetic nanowire systems—atomic-sized AlN nanowires with additional Mn impurities—are investigated employingab initioconstrained spin density functional theory calculations and nonequilibrium Green’s functions formalism. The analyzed nanowire structures exhibit a stress-induced phase transition, between würtzite and graphite-like configurations. In these quasi-one dimensional systems, the surface states ensure the basic prerequisite in establishing spin and charge transfer, by reducing the relatively large bandgap of the group III nitride semiconductor. The results show in how far this phase transition affects the surface states, focusing on the consequences which appear in the spin-filtering processes.

scholarly journals Density Functional Theory Calculations on Nitrated Boroxines as Possible High Energy-Density Materials

2017 ◽  
Vol 117 (2) ◽  
pp. 27 ◽  
Author(s):  
Lisa M. Ina ◽  
David W. Ball
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Minimum Energy ◽  
Normal Modes ◽  
Density Functional Theory Calculations ◽  
Combustion Products ◽  
High Energy ◽  
High Energy Density ◽  
Energy Materials ◽  
Functional Theory

Density functional theory calculations were performed on a series of nitroboroxine molecules (cyclo-[BO]3-[NO2]xH3-x, x = 1 – 3) to determine their thermodynamic properties and assess them as potential high energy materials.  Minimum-energy geometries of four boroxine molecules were determined, along with their normal modes of vibration.  Analysis of the energies of the molecules and their possible decomposition and combustion products suggests an energy contact comparable to that of TNT.

scholarly journals Nanometer-size Na cluster formation in micropore of hard carbon as origin of higher-capacity Na-ion battery

2021 ◽  
Vol 7 (1) ◽  
Author(s):  
Yong Youn ◽  
Bo Gao ◽  
Azusa Kamiyama ◽  
Kei Kubota ◽  
Shinichi Komaba ◽  
...  
Keyword(s):  
Density Functional ◽  
Cluster Formation ◽  
High Capacity ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
High Energy Density ◽  
Hard Carbon ◽  
Functional Theory ◽  
Nanometer Size ◽  
Li Ion

AbstractDevelopment of high-energy-density anode is crucial for practical application of Na-ion battery as a post Li-ion battery. Hard carbon (HC), though a promising anode candidate, still has bottlenecks of insufficient capacity and unclear microscopic picture. Usage of the micropore has been recently discussed, however, the underlying sodiation mechanism is still controversial. Herein we examined the origin for the high-capacity sodiation of HC, based on density functional theory calculations. We demonstrated that nanometer-size Na cluster with 3–6 layers is energetically stable between two sheets of graphene, a model micropore, in addition to the adsorption and intercalation mechanisms. The finding well explains the extended capacity over typical 300 mAhg−1, up to 478 mAhg−1 recently found in the MgO-templated HC. We also clarified that the MgO-template can produce suitable nanometer-size micropores with slightly defective graphitic domains in HC. The present study considerably promotes the atomistic theory of sodiation mechanism and complicated HC science.

scholarly journals Effect of mechanical strain on the Dirac surface states in the (0001) surface and cohesive energy of the topological insulator Bi2Se3

2021 ◽  
Author(s):  
Soumendra Kumar Das ◽  
Prahallad Padhan
Keyword(s):  
Density Functional Theory ◽  
Topological Insulator ◽  
First Principles ◽  
Cohesive Energy ◽  
Density Functional ◽  
Dirac Point ◽  
Mechanical Strain ◽  
Surface States ◽  
Density Functional Theory Calculations ◽  
Functional Theory

The band gap (Eg) engineering and Dirac point tuning of the (0001) surface of 8QLs (quintuple layers) thick Bi2Se3 slab are explored using the first-principles density functional theory calculations by...

scholarly journals A new 2D auxetic CN2 nanostructure with high energy density and mechanical strength

2021 ◽  
Vol 23 (7) ◽  
pp. 4353-4364
Author(s):  
Qun Wei ◽  
Ying Yang ◽  
Alexander Gavrilov ◽  
Xihong Peng
Keyword(s):  
Molecular Dynamics ◽  
Density Functional Theory ◽  
Energy Density ◽  
Mechanical Strength ◽  
Density Functional ◽  
Density Functional Theory Calculations ◽  
High Energy ◽  
High Energy Density ◽  
Two Dimensional ◽  
Functional Theory

The existence of a new two dimensional CN2 structure was predicted using ab initio molecular dynamics (AIMD) and density-functional theory calculations.

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