Temperature dependence of positron trapping rate at lattice vacancies

The positron trapping rate at a lattice vacancy in a metal may not vary in the manner assumed by Seeger. A correct interpretation of quenched cadmium data does not confirm a $\text{T}{}^{\mathrm{<mtext>?1</mtext><mtext>2</mtext>}}$ dependence for the trapping rate.     

Electronic structure and stability of nonstoichiometric titanium monoxide TiO y with structural vacancies in one of the sublattices

The electronic structure of nonstoichiometric titanium monoxide TiO _y with different compositions y, which contains structural vacancies either in the metallic sublattice or in the nonmetallic sublattice, has been investigated using the supercell method within the DFT-GGA approximation with pseudopotentials. The cases of ordered and disordered arrangements of vacancies have been considered. It has been found that the complete removal of vacancies from the sublattice is energetically unfavorable, and the ordering of oxygen vacancies according to the type of the Ti₆O₅□₁ superstructure, as well as titanium vacancies according to the Ti₅?₁O₆ type, does not lead to the stabilization of the B1 basic structure of titanium monoxide.     

Ffect of vacancies on the residual resistivity of ordered alloys with the face-centered cubic lattice

The paper permits a theoretical study of the effect of vacancies at the sites of the crystal lattice of a binary ordered substitutional alloy with the face-centered cubic lattice on its residual resistivity. The dependence of the electrical resistivity on the composition of the alloy and the temperature of annealing is studied.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii Fizika, No. 10, pp. 84–88, October, 1971.     

Longitudinal magnetoresistance of platinum: The influence of lattice vacancies

The longitudinal magnetoresistance of polycrystalline platinum wires has been measured in magnetic fields up to 45 kOe at liquid helium temperatures. The deviations from Kohler's rule found depend on the concentration of quenched-in vacancies, and are interpreted as due to the contribution of single vacancies in platinum to the small angle scattering of electrons. The small-angle scattering may also be responsible for the linear magnetoresistance of platinum in high magnetic fields.     

Effect of vacancies in the lattice of an oxide on interaction with films of metals

It is shown that oxygen vacancies in the lattice of an oxide, being acceptor centers, facilitate ionic interaction in contact with films of metallic condensates and increase adhesion at the interface.Translated from Izvestiya Vysshikh Uchebnykh Zavedenii, Fizika, No. 10, pp. 45–49, October, 1986.     

A thermodynamic model of ordering of nonstoichiometric titanium monoxide TiO y with structural vacancies in the oxygen and titanium sublattices

A thermodynamic model of ordering of nonstoichiometric titanium monoxide TiO _y with structural vacancies in the oxygen and titanium sublattices has been developed taking into account the long-range Coulomb interactions. Methods for calculating the internal energy and entropy of this compound have been proposed. The free energy is represented in the form of a function of long-range order parameters, stoichiometry, and temperature. It has been found that the order-disorder phase transition in the titanium monoxide should occur according to the mechanism of a first-order phase transition. The calculated dependences of the critical values of the long-range order parameters and temperatures on the composition y have demonstrated that, when the composition deviates from stoichiometry, the disordering of structural vacancies in different sublattices should proceed at different temperatures.     

Explanation of atomic displacement around lattice vacancies in diamond based on electron delocalization

The relationship between unpaired electron delocalization and nearest-neighbor atomic relaxations in the vacancies of diamond has been determined in order to understand the microscopic reason behind the neighboring atomic relaxation. The Density Functional Theory (DFT) cluster method is applied to calculate the single-electron wavefunction of the vacancy in different charge states. Depending on the charge and spin state of the vacancies, at outward relaxations, 84-90% of the unpaired electron densities are localized on the first neighboring atoms. The calculated spin localizations on the first neighboring atoms in the ground state of the negatively charged vacancy and in the spin quintet excited state of the neutral vacancy are in good agreement with Electron Paramagnetic Resonance (EPR) measurements. The calculated spin localization of the positively charged vacancy contrasts with the tentative assignment of the NIRIM-3 EPR signal to this center in (p-type) semiconductor diamond. The sign of the lattice relaxation in the diamond vacancy is explained based on the effect of electron delocalization on nearest-neighbor ion-ion screening, and also its effect on the bond length of neighboring atoms.     

Equilibrium concentration of lattice vacancies in magnetic alloys with interstitial atoms

In this paper we have studied the simultaneous influence of interstitial atoms, magnetic ordering and atom ordering on the equilibrium concentration of lattice vacancies in binary alloys with body centered lattice of -brass type. In the course of calculation we took into account the interaction between nearest neighbouring atoms and we neglected correlations between atoms.     

Migration of vacancies and impurities on the (111) surface of a face-centered cubic lattice

The paper presents an analytic study of impurity atom movements over the (111) surface of a face-centered cubic lattice initiated by the diffusion of vacancies. If multiple collisions of a single impurity with vacancies are taken into account, impurity movement acquires the character of Brownian movement. At long times, the time dependence of the mean-square displacement of the impurity insignificantly differs from linear, and its spatial distribution is close to normal, which allows us to introduce a diffusion coefficient. An analytic equation obtained for this diffusion coefficient differs from the product of the diffusion coefficient of vacancies by their relative concentration by a numerical factor only.     

Dechanneling of electrons by thermally produced lattice vacancies in the crystals of alkali halides

Single crystals of NaCl, KCl and KI were heat treated at various elevated temperatures. Lattice vacancies generated in the crystals are found to dechannel the incident energetic electrons. A factor for the increase of the energy loss of electrons due to dechanneling is determined, which is observed to be an increasing function of the concentration of lattice vacancies.     

Monte Carlo calculation of the concentration of lattice vacancies by the method of overlapping distributions

The free energy of formation of vacancies in rare gas crystals is evaluated directly from Monte Carlo simulation of a perfect crystal and a crystal containing a vacancy, without the help of intermediate systems. For solid argon at high temperature we find ΔG_v = 1970 cal/mole - 3.1 k_BT.     

Effects due to field displacement of charged vacancies in the crystal lattice of cadmium sulfide

In single crystals of CdS with indium electrodes an asymmetry in the volt-ampere characteristic has been discovered which develops after the passage of large currents at elevated temperatures. A change in the resistivity of the specimen in a direction from the cathode to the anode is simultaneously observed, associated with the high-temperature drift of charged vacancies.     

Effect of high pressure on the period of the basis lattice and concentration of vacancies in titanium monoxide TiO

The results of the experiment on the thermobaric annealing of titanium monoxide with a B1 cubic structure at a temperature of 2273 K have been analyzed. The analysis of these results has shown that an increase in the initial period of the lattice from 417.6 to 418.0 pm after processing at a pressure of 3 GPa and to 418.5 pm at a pressure of 6 GPa is due to the filling of vacant sites of the crystal structure with atoms. The ab initio quantum calculations indicate that the equilibrium period of the lattice should increase monotonically by 2% at a decrease in the concentration of vacancies from 16.7 to 0%. After aging the samples under normal conditions, the period of the lattice is no more than 421.0 pm and the concentration of vacancies is no lower than 11% because of the instability of the structure at lower concentrations of vacancies.