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Copyright of Scientia et Technica is the property of Scientia et Technica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

Copyright of Scientia et Technica is the property of Scientia et Technica and its content may not be copied or emailed to multiple sites or posted to a listserv without the copyright holder's express written permission. However, users may print, download, or email articles for individual use. This abstract may be abridged. No warranty is given about the accuracy of the copy. Users should refer to the original published version of the material for the full abstract. (Copyright applies to all Abstracts.)

By using a four-interaction interionic potential, constant-energy (classical microcanonical ensemble) molecular dynamics simulations, at room temperature, A g + ionic positions in α-RbAg4I5 compound are reported. In this crystal structure (cubic with a = 11.23934(3) Å and P4132 as space group) a new site has been found. The unit cell has 16- A g + ions, and its disordered partial occupancies have been the subject of discussion. Some authors report 72 [ = 24(e) + 24(e) + 8(c) + 4(b) + 12(d) or Ag1, Ag2, Ag3, Ag4, Ag5] sites with equal vacancy probabilities (Bradley and Greene), 60 [ = 24(e) + 24(e) + 8(c) + 4(b) or Ag1, Ag2, Ag3, Ag4 respectively] with different probability (Geller), 56 [ = 24(e) + 24(e) + 8(c) + 4(b) or Ag1, Ag2, Ag3] with different probability and 4 sites having zero probability (Hull et al). We report 96 interstitial sites [ = 24(e) + 24(e) + 8(c) + 4(b) + 12(d) + 24(e) or Ag1, Ag2, Ag3, Ag4, Ag5, Ag6, respectively] with different probabilities. The new site was denoted as Ag6 with 0.77% similar to Ag5 (∼0.66%). Good results (occupancy probabilities) compared to experimental data were found. [ABSTRACT FROM AUTHOR]

A rigid-ion empirical pairwise potential for RbAg I including Coulomb (long range), Born–Mayer (short range), charge–dipole and dipole–quadrupole (Van der Waals) interactions, has been tested by molecular dynamics simulation with a statistical ensemble where the number of particle, volume, and total energy are constant, non-pressure (P = 0), and as space group were used. Structural (radial, pair, distribution function) and dynamical behaviour (mean square function) of rubidium, iodines, and silvers were evaluated and compared to experimental data reported at room temperature. The potential parameters were taken from different works. [ABSTRACT FROM AUTHOR]

Electrical Impedance Spectroscopy (EIS) was used to study the electrical properties of the (1 − x)CsHSeO4–xKHSeO4 binary system with concentrations x = 0.0 and 0.1. The results show a higher proton-conduction phase above 80°C for both concentrations, however, while DC conductivity of CsHSeO4 shows a gradual change to higher values in the 80–118°C temperature range, the 0.9CsHSeO4–0.1KHSeO4 concentration reveals an abrupt change at about 80°C to an intermediate temperature phase. The observed behavior for the doped sample was modeled using a trial free-energy density, based on the concentration of mobile ions, that takes into account the formation of defects, configurational and phonon entropies, and defect-defect interactions. By minimising the free-energy density one obtains two roots for the carrier concentration at a given temperature, which corresponds to a stable and metastable configuration. It is possible to characterise the phase behavior of the system by means of temperature and two model parameters, which depend on the crystalline properties of the system, but not on temperature. One can successfully explain the conductivity behavior of the system by changing the model parameters if it is assumed that its variations are due to the carriers density. [ABSTRACT FROM AUTHOR]

The solid electrolyte transition in NaI-AgI was studied by electrical conductivity measurements. The addition of NaI stabilizes the α - Β phase boundary of AgI, decreases the total ionic conductivity of a αAgI and modifies their values in the α y Β phases of AgI. The conductivity data were analyzed by considering that the ionic carrier density is the main source of ts variation through this solid electrolyte transition. Thus, by using a previously proposed model trial free-energy density for the equilibrium defects concentration, we were able to reproduce the conductivity change observed in NaI- AgI at 420 K. [ABSTRACT FROM AUTHOR]

Silver iodide is a prototype compound of superionic conductors that allows ions to flow through its structure. It exhibits a first-order phase transition at 420 K, characterized by an abrupt change in its ionic conductivity behavior, and above this temperature, its ionic conductivity increases by more than three orders of magnitude. Introducing small concentrations of carbon into the silver iodide structure produces a new material with a mixed conductivity (ionic and electronic) that increases with increasing temperature. In this work, we report the experimental results of the ionic conductivity as a function of the reciprocal temperature for the (AgI) x - C (1-x) mixture at low carbon concentrations ( x = 0.99, 0.98, and 0.97). The ionic conductivity behavior as a function of reciprocal temperature was well fitted using a phenomenological model based on a random variable theory with a probability distribution function for the carriers. The experimental data show a proximity effect between the C and AgI phases. As a consequence of this proximity behavior, carbon concentration or temperature can control the conductivity of the (AgI) x - C (1-x) mixture.

Copper oxide is a widely studied compound in wastewater decontamination, hydrogen production, solar cell production, and sensor fabrication. In recent years, many architectures and structures with the potential for developing clean technologies have been synthesized. A procedure by thermal oxidation to grow electrical insolate Cu2O films on copper surfaces in an air atmosphere was developed. The results of the morphological and structural characterization of the copper oxide layers evidence the presence of Cu2O polycrystalline films. The films have polyhedral architectures of approximately 1.4 μm thickness and are electrically insulating. A novel copper resistive furnace was built using this copper oxide film which was used as an electrical insulator between the electrical resistance of the heater and the surface of the copper thermal block. The application improves the efficiency of the resistive furnace in terms of the temperature reached and the thermal coupling response time relative to the performance of conventional furnaces using ceramic insulation. Over the entire operating temperature range explored for the same power supply, the copper oxide-coated furnace achieved higher temperatures and faster response times than the traditionally coated furnace.

The superionic conductor, solid state, and body-centered cubic structure, silver iodide at room temperature, has been studied via molecular dynamics simulations. The calculated results using pairwise Coulomb-Buckingham potential, zero pressure on the sample, a semi-rigid model system of 1000 Ag and 1000 I ions, (NVE) as a statistical ensemble, and an effective charge of Z=0.63 for the pairs Ag-Ag and I-I, were found to be consistent with experimental data and one study using Z=0.60, different potential, and simulation software. For the pair Ag-I, there is a discrepancy due to the high silver ion diffusion. The calculated value of the diffusion constant of the silver ion is greater than iodide ion. The dynamic transport properties (mean square displacement, velocity autocorrelation function) results indicated typical behavior reported by other authors, using different potentials in their DM simulations for iodine and silver ions.