Search results for "Density Functional Theory."
showing 10 items of 935 documents
The effect of Zn vacancies and Ga dopants on the electronic structure of ZnO:Ab initiosimulations
2012
Zinc oxide modied by metal dopants can be used as a low-cost material for production of transparent conducting lms. Its optical and electronic properties vary with the type and the concentration of dopants. In this study we have performed rst-principle calculations on ZnO with Zn vacancies and that with Ga dopants in wurtzite type hexagonal morphology using density functional theory approach. Dependence of the electronic properties on the concentration of dopants has been studied using supercells of dierent sizes.
Elastic, electronic and optical properties of boron- and nitrogen-doped 4,12,4-graphyne nanosheet
2020
Abstract The effects of boron (B) and nitrogen (N) dopants on 4,12,4-graphyne have been systematically investigated with density functional theory (DFT) calculations. The charge density analysis reveals that the N dopant at the sp-site destroys the acetylenic linkage in 4,12,4-graphyne, but instead tends to form a polar bond. The B- and N-doped 4,12,4-graphyne systems exhibit p- and n- semiconductor characters, respectively. Some obvious spin splitting polarizations can be observed in their band structures and DOS. Moreover, there is a giant difference in effective masses between electrons and electron holes, especially for B-doped 4,12,4-graphyne at C5 site. The directional electron and el…
First-principles insight into CO hindered agglomeration of Rh and Pt single atoms on m-ZrO2
2020
In this first-principles study we evaluate the thermodynamic and kinetic stability of Rh and Pt single-atoms (SAs) and subnano clusters on the monoclinic zirconia surface with and without a CO atmosphere. To address the kinetic stability and agglomeration of SAs to clusters and nanoparticles, a non-equilibrium nanothermodynamic approach is developed and parametrised using data computed with density functional theory. The bare subnano clusters are more stable than SA and become more so with increasing size, which means the agglomeration is always favoured. CO binds strongly to the single atoms and clusters, and our atomistic thermodynamics treatment indicates that some CO will be present eve…
First-principles calculations of the atomic and electronic structure ofFcenters in the bulk and on the (001) surface ofSrTiO3
2006
The atomic and electronic structure, formation energy, and the energy barriers for migration have been calculated for the neutral O vacancy point defect F center in cubic SrTiO3 employing various implementations of density functional theory DFT. Both bulk and TiO2-terminated 001 surface F centers have been considered. Supercells of different shapes containing up to 320 atoms have been employed. The limit of an isolated single oxygen vacancy in the bulk corresponds to a 270-atom supercell, in contrast to commonly used supercells containing 40– 80 atoms. Calculations carried out with the hybrid B3PW functional show that the F center level approaches the conduction band bottom to within 0.5 eV…
Revealing the correlation between real-space structure and chiral magnetic order at the atomic scale
2017
We image simultaneously the geometric, the electronic, and the magnetic structures of a buckled iron bilayer film that exhibits chiral magnetic order. We achieve this by combining spin-polarized scanning tunneling microscopy and magnetic exchange force microscopy (SPEX) to independently characterize the geometric as well as the electronic and magnetic structures of nonflat surfaces. This new SPEX imaging technique reveals the geometric height corrugation of the reconstruction lines resulting from strong strain relaxation in the bilayer, enabling the decomposition of the real-space from the electronic structure at the atomic level and the correlation with the resultant spin-spiral ground sta…
Trapping of 27 bp–8 kbp DNA and immobilization of thiol-modified DNA using dielectrophoresis
2006
Dielectrophoretic trapping of six different DNA fragments, sizes varying from the 27 to 8416 bp, has been studied using confocal microscopy. The effect of the DNA length and the size of the constriction between nanoscale fingertip electrodes on the trapping efficiency have been investigated. Using finite element method simulations in conjunction with the analysis of the experimental data, the polarizabilities of the different size DNA fragments have been calculated for different frequencies. Also the immobilization of trapped hexanethiol- and DTPA-modified 140 nm long DNA to the end of gold nanoelectrodes was experimentally quantified and the observations were supported by density functiona…
Dense ionic fluids confined in planar capacitors: in- and out-of-plane structure from classical density functional theory
2016
The ongoing scientific interest in the properties and structure of electric double layers (EDLs) stems from their pivotal role in (super)capacitive energy storage, energy harvesting, and water treatment technologies. Classical density functional theory (DFT) is a promising framework for the study of the in- and out-of-plane structural properties of double layers. Supported by molecular dynamics simulations, we demonstrate the adequate performance of DFT for analyzing charge layering in the EDL perpendicular to the electrodes. We discuss charge storage and capacitance of the EDL and the impact of screening due to dielectric solvents. We further calculate, for the first time, the in-plane str…
Electronic structure, lattice dynamics, and optical properties of a novel van der Waals semiconductor heterostructure: InGaSe2
2017
There is a growing interest in the property dependence of transition metal dichalcogenides as a function of the number of layers and formation of heterostructures. Depending on the stacking, doping, edge effects, and interlayer distance, the properties can be modified, which opens the door to novel applications that require a detailed understanding of the atomic mechanisms responsible for those changes. In this work, we analyze the electronic properties and lattice dynamics of a heterostructure constructed by simultaneously stacking InSe layers and GaSe layers bounded by van der Waals forces. We have assumed the same space group of GaSe, $P\overline{6}m2$ as it becomes the lower energy conf…
Mode expansion for the density profiles of crystal–fluid interfaces: hard spheres as a test case
2012
We present a technique for analyzing the full three-dimensional density profiles of a planar crystal-fluid interface in terms of density modes. These density modes can also be related to crystallinity order parameter profiles which are used in coarse-grained, phase field type models of the statics and dynamics of crystal-fluid interfaces and are an alternative to crystallinity order parameters extracted from simulations using local crystallinity criteria. We illustrate our results for the hard sphere system using finely-resolved, three-dimensional density profiles from density functional theory of fundamental measure type.
Charge-transfer interactions between fullerenes and a mesoporous tetrathiafulvalene-based metal–organic framework
2019
The design of metal–organic frameworks (MOFs) incorporating electroactive guest molecules in the pores has become a subject of great interest in order to obtain additional electrical functionalities within the framework while maintaining porosity. Understanding the charge-transfer (CT) process between the framework and the guest molecules is a crucial step towards the design of new electroactive MOFs. Herein, we present the encapsulation of fullerenes (C60) in a mesoporous tetrathiafulvalene (TTF)-based MOF. The CT process between the electron-acceptor C60 guest and the electron-donor TTF ligand is studied in detail by means of different spectroscopic techniques and density functional theor…