We have systematically investigated the influence of oxygen vacancy defects on the structural, electronic and magnetic properties of La(1-x)Sr(x)MnO3 (x = 1/3) film by means of ab initio calculations using bare GGA as well as GGA+U formalism, in the latter of which, the on-site Coulombic repulsion parameter U for Mn 3d orbital has been determined by the linear response theory. It is revealed th...

Isolated point defects possessing a high spin ground state and below-band-gap excitation may play a key role in realizing solid state quantum bits in semiconductors which are the basic building blocks of quantum computers. The silicon vacancy in silicon carbide provides these features, making it a feasible candidate in this special and emerging field of science. However, the exact nature of the...

The traditional picture of a carbon nanotube as a rolled graphene sheet implies that the mechanisms of intra-layer atomic processes in the two systems should be qualitatively similar. Using density-functional theory and tight-binding methods we show that the mechanism of single vacancy migration in nanotubes is different from that in graphite, as the curvature of the nanotube atomic network bre...

The quantum Density Functional Theory (DFT) model of a single atom vacancy on the basal graphite surface is first validated through comparison of the theoretical vibrational spectra of the fully hydrogenated defect with the corresponding High Resolution Energy Loss Spectroscopy (HREELS) spectra. We then proceed to investigate atmospheric molecules adsorption on vacancy defects on the (0001) gra...

Scanning-tunneling microscopy and density-functional theory have been employed to identify the spatial correlation between an oxygen vacancy and the associated Ce(3+) ion pair in a defective CeO(2)(111) film. The two Ce(3+) ions can occupy different cationic shells around the vacancy. The resulting variation in the chemical environment leads to a splitting of the filled Ce(3+) f levels, which i...

Extensive experimental work has been carried out to characterize the stable Na-vacancy ordering patterns at various compositions of layered NaxCoO2. However, contradictions and debates prevail in the literature, particularly at high Na concentrations x 0.5. Understanding of the exotic electronic properties in this system requires a thorough understanding of the Na-vacancy structural orderings. ...

2014 Target and projectile K x-ray cross-sections produced in collisions of Nb projectiles with a series of targets (Zt = 6 68) are reported for energies of 100, 160 and 200 MeV. Various K-vacancy production theories were tested over this broad range including electron promotion with vacancy sharing (molecular model), direct excitation (ECPSSR theory), modified binary encounter approximation (B...

The interaction of fullerenes with transition metal surfaces leads to the development of an atomic network of ordered vacancies on the metal. However, the structure and formation mechanism of this intricate surface reconstruction is not yet understood at an atomic level. We combine scanning tunneling microscopy, high resolution and temperature programmed-x-ray photoelectrons spectroscopy, and d...

asphaltenes are the n-pentane or n-heptane insoluble fractions of crude oil that remain in solution under reservoir temperature and pressure conditions. they are destabilized and start to precipitate when the pressure, temperature and/or composition changes occur during primary production. the precipitated asphaltene particles will then grow in size and may start to deposit onto the production ...

Stability test of nanotubes with presence of single vacancies has been performed by means of tight-binding molecular dynamics and electron–ion dynamics within the framework of the density functional theory. A 4 ( A diameter nanotube having a single vacancy with three dangling bonds has been found to retain its cylindrical shape under high temperature around 4000 K; despite its large internal st...