D-glucose derivatives of dihydropyrido-[2,3-d:6,5-d′]-dipyrimidine-2, 4, 6, 8(1H,3H, 5H,7H)-tetraone (GPHs) have been synthesized and investigated as corrosion inhibitors for mild steel in 1M HCl solution using gravimetric, electrochemical, surface, quantum chemical calculations and Monte Carlo simulations methods. The order of inhibition efficiencies is GPH-3 > GPH-2 > GPH-1. The results further showed that the inhibitor molecules with electron releasing (-OH, -OCH₃) substituents exhibit higher efficiency than the parent molecule without any substituents. Polarization study suggests that the studied compounds are mixed-type but exhibited predominantly cathodic inhibitive effect. The adsorption of these compounds on mild steel surface obeyed the Langmuir adsorption isotherm. SEM, EDX and AFM analyses were used to confirm the inhibitive actions of the molecules on mild steel surface. Quantum chemical (QC) calculations and Monte Carlo (MC) simulations studies were undertaken to further corroborate the experimental results.

Visible photoluminescence (PL) broad bands are observed in the Raman spectra of SiC nanoparticles (np-SiC) with diameters ranging from 10 to 25 nm. The phenomenon is studied versus the particle size, chemical composition, annealing, and oxidation treatments. In the case of quasistoichiometric np-SiC, excitation by 514-nm radiation gives rise to broad red PL emissions mainly enhanced by the amorphous fraction of the particles and by the surface chemical disorder induced by oxidation. The PL spectra are quantitatively analyzed using numerical methods based on cluster approaches. PL bands are calculated as a function of the cluster geometry and defects (carbon and silicon vacancies), as well as the oxygen location within np-SiC sites. The relevance of this numerical analysis is discussed to account for the main features of the PL broad structure. The PL signature in SiC nanopowders can be used to monitor the physical organization of the np-SiC and to point out their amorphous structure fraction, surface states, and the defect contents.

We present a band structure approach in connection with a molecular dynamics cluster optimization that accounts for various structural modifications related to the nonstoichiometry of ${\mathrm{LiNbO}}_3$ crystals. Variation of optical properties with the deviation from the stoichiometric composition can be understood within this approach. The particular role of the electron-phonon contributions to the electro-optic coefficient is shown. Model calculations yield a large dependence of the electro-optic coefficient $r_{22}$ on the crystal composition, in agreement with the experimental data. The observed minimum of the $r_{22}$ coefficient versus nonstochiometry is explained within a microscopic approach. The $r_{33}$ tensor component shows substantially different behavior versus the stoichiometry.