No abstract

A model resulting in charge ordering (CO) similar to that observed in cuprate superconductors is under study. It includes strong long-range electron-phonon interaction (EPI) and high density of correlated carriers. Coexistence of large bipolarons and delocalized carriers is a feature of such system. We develop generalized variation method to calculate the bipolaron size (CO period) in the ground normal state of such system at various doping. The approach allows the revealing of a possible physical reason of strongly different doping behavior of the CO wave vector in different cuprates. Obtained doping dependences of the CO period and temperature of the CO decay demonstrate quantitative agreement with those observed in cuprates. Predicted in the suggested approach ratio of the CO wave vector to the wave vector of the high-energy anomaly (HEA) in ARPES spectrum is in consent with that in cuprates. Calculated resonant x-rays scattering on the CO emerging in the model is in good agreement with experiments on cuprates including the asymmetry of the CO peaks' cross-section. A gap arises in the spectrum of delocalized carriers near antinodal direction due to their scattering on the periodic potential created by autolocalized carriers, analogously to photon crystal effect.

No abstract

This research evaluates the inhibitory effect of L-amino acids (AAs) with different side chain lengths on Fe (100) surfaces implementing Monte Carlo (MC) simulation. A quantitative and qualitative description of the adsorption behavior of AAs on the iron surface has been carried out. Calculations have shown that the absolute values of the adsorption energy of L-amino acids increase with side chain prolongation; they are also determined by the presence of heteroatoms. The maximum absolute value of the adsorption energy AAs on the iron surface in accordance with the side chain classification increases in the following sequence: Glu (acidic) < Gln (polar) < Trp (nonpolar) < Arg (basic). AAs from nonpolar and basic groups have the best adsorption ability to the iron surface, which indicates their highest inhibitory efficiency according to the results of the MC simulation. The calculation results agree with the experimental data.

The peptide molecular group participates in donor-accepting processes by interacting with the metal surface. It boosts adsorption interaction with the metal surface which enhances the inhibitory effect.

No abstract

The hydration of the basal surfaces of kaolinite is studied by theoretical methods. The cluster method was used to simulate the positions of atoms. The positions of the atoms of the basal surfaces of dry and hydrated minerals are optimized by minimizing the total energy in the Hartree–Fock approximation. The adsorption energies of water molecules were calculated taking into account the fourth-order correlation corrections of Møller–Plesset perturbation theory. The formation of the IR spectrum of kaolinite in the range of wave numbers 2500–4500 cm−1 is studied. The experimentally observed effect of the change in relative intensity and position of the band with a change in the moisture content of the sample is interpreted.

This study presents data on the IR spectra of kaolinite at a moisture of 26% and after drying. The preparation of moistened samples was made with distilled water, and the solutions of NaCl with limiting and 50% of limiting concentrations at a temperature of 21 °C. To experimentally evaluate the effect of the interaction between liquid water and sorbing basal surfaces of kaolinite on the profile of the IR spectrum bands, the spectra of distilled water and NaCl solutions were additionally studied. Comparison of the band profiles in the wavenumber range of 2750–4000 cm−1 for kaolinite samples allows the conclusion that, when going from distilled water to the most saline water, the adsorption effect is inferior to the effect of solvation, and it decreases with increasing salinity. During drying of the samples, an increase in the peak intensities of the bands in the wavenumber range of 3550–3750 cm−1 is observed. Observed spectral variations are qualitatively interpreted by the results of calculations performed by the DFT method with the XLYP exchange–correlation potential. The presented data can be used to test theoretical approximations and computer models for calculating the structure and properties of moist minerals and salt adsorption mechanisms.