scholarly journals Green Afterglow of Undoped SrAl2O4

Nanomaterials ◽  
2021 ◽  
Vol 11 (9) ◽  
pp. 2331
Author(s):  
Bao-Gai Zhai ◽  
Yuan-Ming Huang
Keyword(s):  
First Principles ◽  
Density Functional Calculations ◽  
Glow Curve ◽  
Density Functional ◽  
Trap Depth ◽  
Peak Temperature ◽  
Solution Combustion ◽  
Densities Of States ◽  
Thermoluminescence Glow Curve ◽  
Trap Levels

Undoped SrAl2O4 nanocrystals were obtained via solution combustion using urea as fuel. The afterglow properties of undoped SrAl2O4 were investigated. Green afterglow from undoped SrAl2O4 is visible to the human eye when the 325 nm irradiation of a helium–cadmium laser (13 mW) is ceased. The afterglow spectrum of undoped SrAl2O4 is peaked at about 520 nm. From the peak temperature (321 K) of the broad thermoluminescence glow curve, the trap depth of trap levels in undoped SrAl2O4 is estimated to be 0.642 eV using Urbach’s formula. Based on first-principles density functional calculations, the bandstructures and densities of states are derived for oxygen-deficient SrAl2O4 and strontium-deficient SrAl2O4, respectively. Our results demonstrate that the green afterglow of undoped SrAl2O4 originates from the midgap states introduced by oxygen and strontium vacancies. The observation of green afterglow from undoped SrAl2O4 helps in gaining new insight in exploring the afterglow mechanisms of SrAl2O4-based afterglow materials.

A Comparison between Polyatecylene and Polycarbonitrile

1993 ◽  
Vol 48 (1-2) ◽  
pp. 159-164 ◽  
Author(s):  
Michael Springborg
Keyword(s):  
Comparative Study ◽  
Electronic Properties ◽  
Ground State ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Form Factors ◽  
Model Calculations ◽  
Densities Of States ◽  
Momentum Distributions

Abstract Results of a theoretical, comparative study of the electronic properties of trans-polyacetylene and polycarbonitrile are reported. Polyacetylene consists of zigzag chains of CH units, whereas polycarbonitrile has every second CH unit replaced by an N atom. Ground-state properties (structure, electronic bonds and bands, densities of states, momentum distributions, and reciprocal form factors) of the periodic, infinite, isolated chains are studied by means of first-principles, density-functional calculations. It is demonstrated how the presence of the (nitrogen) heteroatoms in the backbone of polycarbonitrile leads to a partial localization of the electrons. In order to investigate charged chains, model calculations are subsequently performed. These indicate solitons but not polarons to be stable. In total, the analysis demonstrates how the combination of information that can be obtained from various experiments provides a detailed description of the compounds.

The Studies of ScB2 (0001) Surfaces from the First-Principles

2014 ◽  
Vol 989-994 ◽  
pp. 688-693
Author(s):  
Hui Zhao ◽  
Qian Han
Keyword(s):  
Energy Density ◽  
Total Energy ◽  
Electronic Properties ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Surface Structures ◽  
Charge Accumulation ◽  
Total Energy Density ◽  
Energy Density Functional

We conduct first-principles total-energy density functional calculations to study the ScB2 (0001) surfaces. The optimized surface structures and electronic properties are obtained. The results show that Sc-terminated surface is thermodynamically more favorable in most of range. The relaxations indicate that it is mainly localized within top three layers and it is less relaxation for Sc-terminated surface. The surface induced features in DOS disappear slowly for the B-terminated surface but vanish rapidly for the Sc-terminated surface. For the Sc-terminated surface, it shows strong metallic property. Simultaneously, both termination surfaces are found charge accumulation relative to the idea surface. Sc-B bonds are strengthened result in the outermost interface spacing are all contracted.

Electronic Structure and Hyperfine Parameters for Hydrogen and Muonium in Silicon

1989 ◽  
Vol 163 ◽  
Author(s):  
Chris G. Van De Walle
Keyword(s):  
Spin Density ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Muon Spin ◽  
Spin Rotation ◽  
Muon Spin Rotation ◽  
Hyperfine Parameters ◽  
Bond Center ◽  
Center Site

AbstractFirst-principles spin-density-functional calculations are used to evaluate hyperfine and superhyperfine parameters for hydrogen and muonium at various sites in the Si lattice. The results can be directly compared with values from muon-spin-rotation experiments, leading to an unambiguous identification of “anomalous muonium” with the bond-center site. The agreement found in this case instills confidence in the general use of spin-density-functional calculations for predicting hyperfine parameters of defects.

Adhesion In NiAl-Cr From First Principles

1995 ◽  
Vol 409 ◽  
Author(s):  
James E. Raynolds ◽  
John R. Smith ◽  
David J. Srolovitz ◽  
G.-L. Zhao
Keyword(s):  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Interfacial Stress ◽  
Work Of Adhesion ◽  
Separation Curve ◽  
Self Consistent

AbstractWe have calculated the work of adhesion (i.e. energy for rigid fracture) and peak interfacial stress for NiAl, Cr, and NiAl–Cr using self-consistent density functional calculations to obtain the complete energy vs. separation curve for each system. Our calculations indicate that the work of adhesion is largest for Cr and smallest for NiAI while those for interfaces of NiAI with Cr are intermediate. We have also estimated that segregation processes could alter the work of adhesion for the AlNi/Cr interface by up to 20% since Al tends to segregate to the free NiAl surface while Ni tends to segregate to the AlNi/Cr interface.

scholarly journals Native point defects in CuIn1−xGaxSe2: hybrid density functional calculations predict the origin of p- and n-type conductivity

2014 ◽  
Vol 16 (40) ◽  
pp. 22299-22308 ◽  
Author(s):  
J. Bekaert ◽  
R. Saniz ◽  
B. Partoens ◽  
D. Lamoen
Keyword(s):  
Charge Carrier ◽  
Point Defects ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
First Principles Calculations ◽  
Photoluminescence Spectra ◽  
Type Conductivity ◽  
Native Point Defects ◽  
Hybrid Density Functional

Starting from first-principles calculations, many experimental observations such as photoluminescence spectra, charge carrier densities and freeze-out can be explained.

Electron small polarons and their transport in bismuth vanadate: a first principles study

2015 ◽  
Vol 17 (1) ◽  
pp. 256-260 ◽  
Author(s):  
Kyoung E. Kweon ◽  
Gyeong S. Hwang ◽  
Jinhan Kim ◽  
Sungjin Kim ◽  
SeongMin Kim
Keyword(s):  
Concentration Dependence ◽  
Electron Mobility ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Small Polaron ◽  
Polaron Hopping ◽  
Polaron Formation ◽  
Hybrid Density Functional ◽  
Small Polarons

Hybrid density functional calculations demonstrate small polaron formation in electron-doped BiVO4, and predict the polaron hopping barrier to increase with lattice constant and also the possible concentration-dependence of electron mobility.

Properties of the Magnetic Hydride YFe2H4 from First Principles Calculations

2003 ◽  
Vol 801 ◽  
Author(s):  
D.J. Singh ◽  
M. Gupta
Keyword(s):  
Magnetic Properties ◽  
Electronic Structure ◽  
First Principles ◽  
Density Functional Calculations ◽  
Density Functional ◽  
Parent Compound ◽  
Laves Phase ◽  
Lattice Expansion ◽  
First Principles Calculations ◽  
Electronic And Magnetic Properties

ABSTRACTYFe2H4 is a ferromagnetic metal with magnetization higher than the Laves phase parent compound, YFe2. Here, the electronic and magnetic properties of YFe2H4 are studied using density functional calculations, in order to elucidate the reasons for this. The electronic structure of YFe2H4 differs from that of YFe2 both because of the lattice expansion upon hydriding and because of chemical interactions involving H. However, the main reason for the increased magnetization is found to be the lattice expansion.

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