Structural transition and the effect of Ca impurities in MgO Σ5(210) grain boundary

The effects of several metalloid (B), metalloid-like (C, P) and nonmetallic impurities (N, O and S) on structure, energetics and mechanical properties of Σ3(1 1 1) and Σ5(2 1 0) grain boundaries (GBs) in ferromagnetic α-Fe have been studied from first principles. For two different concentrations and positions of impurity atoms, the variations in GB properties have been analysed. Most of the impurities enhance the relaxation of the interplanar spacing of the pure grains. Interstitial impurities at both GBs are shown to increase the separation of the grains while substitutional ones in general either do not alter or decrease the grains' separation. It is shown that at the Σ5 GB for all impurity atoms considered the positions in the boundary layer are energetically favoured independently of the interstitial or substitutional site, whereas the enrichment of the Σ3 GB is favoured for the impurities of the interstitial sites as well as for a substitutional P and C. We have found that, in most cases, impurity atoms both in interstitial and substitutional positions at GBs act as embrittlers. Interstitial B, P and C strengthen the Σ3 GB cohesion, and B and C at lower concentrations strengthen the Σ5 GB. All substitutional impurities, except for B, weaken the GBs. The magnetic moments on the impurities are very small and in most cases align antiparallel to the moments on the neighbouring Fe atoms.

The wavevector dependence of the critical fluctuations at the cubic-to-tetragonal structural phase transition in KMnF3 doped with 1% and 10% of KMgF3 has been studied using X-ray scattering techniques. It is found that the introduction of impurities lowers Tc and that the fluctuation-driven first-order transition becomes continuous when the impurity concentration exceeds a certain threshold. At temperatures far above Tc, the temperature dependence of the X-ray critical scattering cross section measured in the samples KMnF3, KMn0.99Mg0.01F3 and KMn0.9Mg0.1F3 is described by the same critical exponents nu and gamma . Contrary to expectation, the magnitude of the anomalous narrow component observed in the critical scattering in pure KMnF3 close to Tc is significantly reduced by the introduction of the impurities.

Tuning the microstructure of biomass-derived hard carbons by controlling the impurity removal process for enhanced Na ion storage performance

Static high pressure diamond anvil cell experiments were performed on threepolycrystalline Zr samples having varying interstitial impurity concentrations. Systematicincrease in transition pressure with the increase in the amount of interstitial impurities isobserved for the martensitic structural phase transition in Zr. Significant room temperature crystal grain growth isalso observed for the two highest purity samples at the transition. In the case of the lowest purity sample interstitial impurities obstruct the transition, while possibly helping impede grain growth—even as the sample is heated to1279 K.

The effect of impurities on TL emission wavelengths of NaCl crystals

Influence of impurities on adsorption of hydrated Y3+ ions on the kaolinite (001) surface

This paper is devoted to studying the influence of Ca, Si, Pb, and Cr impurities (possessing no absorption bands at the wavelength of acting laser irradiation) on the value of bulk laser damage threshold and UV absorption in KDP single crystals. It is shown that for the investigated concentration range (1 divided by 10<SUP>-5</SUP> 1 divided by 10<SUP>-2 mass%</SUP> laser damage threshold essentially decreases with raising the concentration of impurity ions in the crystal lattice. The maximal value of the said characteristic (approximately 40 J/cm<SUP>2</SUP>) is found to be achieved in the case when the concentration of impurities is not less than 1 divided by 10<SUP>-5</SUP> mass%.

The effects of Pb, Ca, and Si impurities on the laser damage threshold and UV absorption of KH2PO4 crystals were studied. The laser damage threshold was found to be ≃6 × 1011 W/cm2 in crystals containing ≃5 × 10–5 wt % and to decrease nonlinearly at higher impurity contents.

Effect of impurities on structural phase transition of displacive type was examined through molecular dynamics simulation. Anharmonic oscillators were arranged on a two-dimensional square lattice with harmonic nearest-neighbor interaction. Local order parameters were calculated with impurities of different strength. Weak impurities affect more strongly than strong inpurities in relative magnitude.

Anomalous magnetic susceptibility of Y 2Fe 3Si 5