Defects always exists in a crystal lattice at temperatures above absolute zero. Our knowledge of defect concentration and mobility is crucial, due to their profound influence on the material properties. By the means of thermodynamics it is possible to estimate defect concentrations at the equilibrium conditions. Near the melting point of pure metals the vacancy fraction is typically about 10−4....

Using first principles based on density functional theory (DFT), the CO, NH3, NO, and NO2 gas adsorbed intrinsic Graphite-like ZnO (g−ZnO) vacancy-deficient g−ZnO were systematically studied. For g−ZnO, adsorption energy of defective systems increased significantly due to introduction Zn vacancy (VZn). Especially, for Zn-vacancy (VZn/g−ZnO) 1.366 eV, 2.540 eV 2.532 respectively. In addition, wi...

Atomic scale computer simulations, validated with experimental data, are used to uncover the factors responsible for defect-induced chemical expansion observed in non-stoichiometric oxides, exemplifi ed by CeO 2 and ZrO 2 . It is found that chemical expansion is the result of two competing processes: the formation of a vacancy (leading to a lattice contraction primarily due to electrostatic int...

The stability and reactivity of the hematite, Fe2O3(0001) surface are studied by density functional theory including an on-site Coulomb term (DFT+U). Even under oxygen rich conditions, the metal-terminated surface is shown to be stable. On this surface termination, the isolated water molecule forms a heterolytically dissociated structure with the OH- group attached to a surface Fe3+ ion and the...

Magnetic resonance is a wrell known tool for the investigation of atomic and molecular motions in solids and a large amount of work has been done in the past on this subject by studies of Zeeman (Ty/J spin-lattice relaxation time and dipolar line widths {To). More recently, the power of the NMR method has been still considerably improved bv the mea­ surements on rotating frame1,2 Tls and dipola...

Transport measurements have revealed several exotic electronic properties of graphene. The possibility to influence the electronic structure and hence control the conductivity by adsorption or doping with adatoms is crucial in view of electronics applications. Here, we show that in contrast to expectation, the conductivity of graphene increases with increasing concentration of vacancy defects, ...

We have investigated the photoluminescence ~PL! from anodic alumina membranes with an ordered nanopore array formed on bulk Al foils. Most of the membranes fabricated by anodization in oxalic acid showed a strong PL peak in the blue. Due to an obvious asymmetry, the PL peak can be Gaussian divided into two bands around 405 and 455 nm, having a slight shift with the sample formed in different ac...

2014 We have studied through capacitance techniques (TSCAP and DLTS) the variation of the introduction rate of defects with the energy of the electrons in n-type silicon irradiated at room temperature. The results obtained provide a direct confirmation of the identification of the observed defects which was proposed in the literature : the Ec 0.39 and Ec 0.23 eV levels, attributed to the divaca...

In this article, we examine the Young modulus of (6, m) boron-nitride nanotubes with vacancy and functionalization defects. We employ molecular dynamics simulations using the Parrinello-Rahman approach. To this end, all systems are modeled with a reactive many-body bond order Tersoff-potential with parameters due to Matsunaga et al [1], which is able to accurately describe covalent bonding. We ...

Large unit cell calculations of the properties of charged point defects in insulators largely neglect dielectric polarization of the crystal, because the periodically repeated cells are so small. Embedded quantum cluster calculations with shell-model crystals, representing a single defect in a large crystal, are able to represent the polarization more realistically. For such embedded quantum cl...