Exploring the Excited States of Vacancy Defects in Silica

1998 ◽  
Vol 540 ◽  
Author(s):  
J. Song ◽  
L. R. Corrales ◽  
H. Jònsson
Keyword(s):  
Density Functional ◽  
Defect Formation ◽  
Initial Study ◽  
Vacancy Defect ◽  
Dynamics Simulation ◽  
Electronic Excitations ◽  
Defect States ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Simulation Methodology

AbstractA study of vacancy defect formation is carried out using a density functional theory molecular dynamics simulation methodology. The objective is to study the effects of electronic excitations in crystalline and non-crystalline silica polymorphs. We present an initial study focusing on the formation energetics of distinct oxygen vacancy defect states in α-quartz.

First-Principles Study of Interaction of Lithium Atoms with (3, 3) Carbon Nanotubes

2014 ◽  
Vol 687-691 ◽  
pp. 4311-4314 ◽  
Author(s):  
Shun Fu Xu ◽  
Ling Min Li
Keyword(s):  
Carbon Nanotubes ◽  
First Principles ◽  
Density Functional ◽  
Vacancy Defect ◽  
Single Wall Carbon Nanotubes ◽  
Generalized Gradient ◽  
Hydrogen Atoms ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Adsorption Mechanisms

In this paper, we have employed first-principles calculations to investigate the adsorption mechanisms of one lithium atom on the sidewalls of 1/2/3 H-adsorbed indefective/defective (3, 3) single-wall carbon nanotubes (CNTs) which have vacancy defects. Our calculations are performed within density functional theory (DFT) under the generalized gradient approximation (GGA) of Perdew, Burke, and Ernzerhof (PBE).Our results show that the lithium atoms strongly binds to the H-adsorbed (3, 3) nanotube. Lithium atoms can chemically adsorb on (3, 3) nanotube with the vacancy defect (MVD) without any energy barrier. The lithium adsorption will enhance the electrical conductivity of the nanotube. Further more, the structure of the (3, 3) nanotube with the MVD and hydrogen atoms will become more stable after the three kinds of lithium adsorption.

CO2 adsorption on single-walled boron nitride nanotubes containing vacancy defects

RSC Advances ◽  
2015 ◽  
Vol 5 (35) ◽  
pp. 27412-27420 ◽  
Author(s):  
Edson Nunes Costa Paura ◽  
Wiliam F. da Cunha ◽  
Luiz Fernando Roncaratti ◽  
João B. L. Martins ◽  
Geraldo M. e Silva ◽  
...  
Keyword(s):  
Density Functional Theory ◽  
Boron Nitride ◽  
Density Functional ◽  
Co2 Adsorption ◽  
Vacancy Defect ◽  
Boron Nitride Nanotubes ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Defect Type

The adsorption of a CO2 molecule on the vacancy defect type of armchair (5,5) and zigzag (10,0) single-walled boron nitride nanotubes was studied based on Density Functional Theory (DFT).

scholarly journals Role of Chemistry and Crystal Structure on the Electronic Defect States in Cs-Based Halide Perovskites

Materials ◽  
2021 ◽  
Vol 14 (4) ◽  
pp. 1032
Author(s):  
Anirban Naskar ◽  
Rabi Khanal ◽  
Samrat Choudhury
Keyword(s):  
Crystal Structure ◽  
Density Functional ◽  
Covalent Bond ◽  
Density Functional Theory Calculations ◽  
Antisite Defect ◽  
Defect States ◽  
Functional Theory ◽  
Electronic Defect ◽  
Constituent Elements

The electronic structure of a series perovskites ABX3 (A = Cs; B = Ca, Sr, and Ba; X = F, Cl, Br, and I) in the presence and absence of antisite defect XB were systematically investigated based on density-functional-theory calculations. Both cubic and orthorhombic perovskites were considered. It was observed that for certain perovskite compositions and crystal structure, presence of antisite point defect leads to the formation of electronic defect state(s) within the band gap. We showed that both the type of electronic defect states and their individual energy level location within the bandgap can be predicted based on easily available intrinsic properties of the constituent elements, such as the bond-dissociation energy of the B–X and X–X bond, the X–X covalent bond length, and the atomic size of halide (X) as well as structural characteristic such as B–X–B bond angle. Overall, this work provides a science-based generic principle to design the electronic states within the band structure in Cs-based perovskites in presence of point defects such as antisite defect.

Study on adsorption of CO and CO2 by graphene gas sensor

2021 ◽  
pp. 2150154
Author(s):  
Wenchao Tian ◽  
Jiahao Niu ◽  
Wenhua Li ◽  
Xiaohan Liu
Keyword(s):  
Gas Sensors ◽  
Active Sites ◽  
Density Functional ◽  
Gas Adsorption ◽  
Experimental Studies ◽  
Detection Accuracy ◽  
Functional Theory ◽  
Vacancy Defects ◽  
Adsorption Of Co ◽  
Detection Characteristics

The two-dimensional (2D) plane of graphene has many active sites for gas adsorption. It has broad application prospects in the field of MEMS gas sensors. At present, there are many experimental studies on graphene gas sensors, but it is difficult to accurately control various influencing factors in the experiments. Therefore, this paper applies the first principle based on density functional theory to study the adsorption and detection characteristics of graphene on CO and CO2. The first-principles analysis method was used to study the adsorption characteristics and sensitivity of graphene. The results show that the inductive graphene has a sensitivity of 1.55% and 0.77% for CO and CO2, respectively. The Stone–Wales defects and multi-vacancy defects have greatly improved the sensitivity of graphene to CO, which is 35.25% and 4.14%, respectively. Introduction of defects increases the sensitivity of detection of CO and CO2, but also improves the selective gas detection material of these two gases. Thus, the control and selectively introducing defects may improve the detection accuracy of the graphene CO and CO2.

A complete ab initio thermodynamic and kinetic catalogue of the defect chemistry of hematite α-Fe2O3, its cation diffusion, and sample donor dopants

2021 ◽  
Author(s):  
Shehab Shousha ◽  
Sarah Khalil ◽  
Mostafa Youssef
Keyword(s):  
Density Functional Theory ◽  
Density Functional ◽  
Defect Formation ◽  
Defect Chemistry ◽  
Cation Diffusion ◽  
Functional Theory ◽  
Migration Barriers ◽  
Hubbard U ◽  
And Migration ◽  
Formation Energies

This paper studies comprehensively the defect chemistry and cation diffusion in α-Fe2O3. Defect formation energies and migration barriers are calculated using density functional theory with a theoretically calibrated Hubbard U...

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