In this paper we report positron lifetime results obtained under high-power steady-state and transient optical excitation. We present a model to analyse the results. The method has been applied to vacancy clusters in natural diamond, for which we self-consistently analyse optoelectronic constants such as optical absorption cross section and hole recombination cross section. The temperature depe...

Ab initio molecular dynamics simulations are employed to investigate the dominant migration mechanism of the gallium vacancy in GaAs as well as to assess its free energy of formation and the rate constant of gallium self-diffusion. Our analysis suggests that the vacancy migrates by second nearest neighbour hops. The calculated self-diffusion constant is in good agreement with the experimental v...

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...

We present a molecular dynamics simulation study of vacancy generation and emission from grain boundaries during curvature-driven grain boundary migration. The U-shaped half-loop bicrystal geometry is employed in order to maintain a constant driving force during boundary migration. Nonlinearities in plots of half-loop grain area versus time indicate the onset of non-steady-state behavior and va...

Ionic vacancy is a by-product in electrochemical reaction, composed of polarized free space of the order of 0.1 nm with a 1 s lifetime, and playing key roles in nano-electrochemical processes. However, its chemical nature has not yet been clarified. In copper electrodeposition under a high magnetic field of 15 T, using a new electrode system called cyclotron magnetohydrodynamic (MHD) electrode ...

We report on the detection of electric field–induced second harmonic generation (EFISHG) from the anode interfaces of reduced and oxidized Fe-doped SrTiO3 (Fe:STO) single crystals. For the reduced crystal, we observe steady enhancements of the susceptibility components as the imposed dc-voltage increases. The enhancements are attributed to a field-stabilized electrostriction, leading to Fe:Ti-O...

The recently discovered iron-based superconductors A(y)Fe(2-x)Se(2) (A=K, Rb, Cs, Tl) show a long-range antiferromagnetic order with an unexpectedly high transition temperature T(N)~550 K and a unique √5×√5 vacancy order. Taking the extended J(1)-J(2) model as a minimal model, we investigate the finite-temperature magnetic phase transitions in a square lattice with a √5×√5 vacancy superstructur...

We study the Bethe ansatz equations for a generalized XXZ model on a one-dimensional lattice. Assuming the string conjecture we propose an integer version for vacancy numbers and prove a combinatorial completeness of Bethe's states for a generalized XXZ model. We nd an exact form for inverse matrix related with vacancy numbers and compute its determinant. This inverse matrix has a tridiagonal f...