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Glucosamine is a natural drug widely used for treating osteoarthritis and is usually left until it expires, which will cause a waste of resources if treated as garbage. However, its molecule contains many heteroatoms, entitling it to be a potential corrosion inhibitor. In this investigation, the corrosion inhibition activities of two types of expired glucosamine drugs (glucosamine hydrochloride and glucosamine sulfate) on carbon steel were estimated by electrochemical methods in the acidic solution. The results demonstrated that the glucosamine drugs were mixed-type corrosion inhibitors. Glucosamine hydrochloride could inhibit the carbon steel corrosion more significantly than that of sulfuric style at the same glucosamine content, suggesting a possible synergistic effect of glucosamine molecules with halide ions. Then, the co-adsorption behaviors of glucosamine sulfate with iodide ions were studied by experimental research, as well as theoretical investigations. The results indicated that the inhibition effect could be significantly enhanced when the glucosamine drug was utilized in combination with iodide ions. The electronic structures played a critical role in the synergistic inhibition of glucosamine drugs and iodide ions. Neutral molecules could interact with the metallic surface vertically through the amino and carbonyl groups, while protonated molecules were able to adsorb on it in parallel with the help of multiple functional groups. Since glucosamine molecules would be protonated and positively charged in the acidic solution, they were difficult to adsorb on the solid surface with metallic cations. When the iodide ions were presented, they preferentially adsorbed on the carbon steel surface and induced it to be negatively charged. Therefore, protonated glucosamine molecules could adsorb on the metallic surface using iodide ions as a bridge and form a protective film to mitigate the carbon steel corrosion.

An extract of cucumber leaves (ECSL) was prepared as a green corrosion inhibitor for carbon steel. Its carbon steel corrosion inhibition performance against 0.5 mol L−1 H2SO4 was investigated using electrochemical methods and scanning electron microscopy (SEM). Its composition was analyzed by gas chromatography and mass spectroscopy (GC−MS). Quantum chemical calculations and molecular dynamics simulations (MDS) were conducted to elucidate the adsorption mechanism of the inhibitor molecules on the carbon steel surface. The results indicated that the inhibition efficiency increases with its increasing concentration. The extract acted as a mixed type corrosion inhibitor, and its inhibition properties were ascribed to the geometric coverage effect induced by its adsorption on the metal surface in accordance with Langmuir’s law. The active components in the extract were identified as mainly organic compounds with functional groups such as aromatic moieties and heteroatoms. The inhibition activities of ECSL are delivered through the ability of the active components to adsorb on the metal surface through their functional groups to form a protective layer which hinders the contact of aggressive substances with carbon steel and thus suppresses its corrosion. This research provides an important reference for the design of green corrosion inhibitors based on plant waste materials.

The molecular and crystal structures of myricetin have been studied using density functional theory. The geometry parameters are calculated based on the optimized molecular structure, and the thermodynamic properties "heat capacity (p m C,), enthalpy (m H) and entropy (m H)" are performed using our selfprogrammed programme, the calculated results are consistent with literature reports. Crystal structures were predicted using the Dreiding force field and refined by DFT-GGA-RPBE method. The crystal form tends to crystalline in P-1 space group. The large calculated band gap (Eg) of the crystal proves it is stable, which is consistent with the conclusion from gas phase. The conduction band (LUCO) is mainly contributed from the p state of C atom and valence band (HOCO) from the p state of O atom. [ABSTRACT FROM AUTHOR]

In the present study, the mechanism of Maillard reaction was investigated using density functional theory calculations. Glucose and aminomethane were used as initial reactants in this study. The calculations show that the Amadori rearrangement reaction is the rate-controlling step with a corresponding energy potential of 402 kJ/mol, the enthalpy change is 219 kJ/mol, which is an endothermic reaction and therefore energy needs to be supplied from outside if the reaction is to proceed. The calculated results are in good agreement with the previous findings and can provide insight into the reaction mechanism of the Maillard reaction. These findings will help further research and find out the correct reaction mechanism. [ABSTRACT FROM AUTHOR]

Three adducts SF4·BF3, SF4·AsF5, and SF4·SbF5 were studied in this work, in gas phase, DFT method was performed to study their molecular structures and thermodynamic properties. The heat of formation was studied at the high level DFT levels. Crystal structures were predicted using the Dreiding force field and refined by DFT-GGA-RPBE method. All the obtained crystal structures belong to the P21/c space group. The lattice energies were predicted to be located between -91.86 and -693.73 kJ/mol at the GGA-RPBE level. Based on the optimized crystal structures, the band gap (ΔEg) and density of state (DOS) were predicted and the calculations indicate that they are semiconductors with the band gap between 2.22 and 2.43 ev. [ABSTRACT FROM AUTHOR]

The molecular and crystal structure of the adduct NF3·BF3 has been studied using complete basis set method (CBS-4M). It shows that the adduct exists in the form of complex but not ionic, the heat of formation of the gas and condensed phase of the adduct are -1266.09 and -1276.37 kJ·mol-1 respectively, which denotes it is stable under atmospheric conditions. The crystal form tends to crystalline in P21/c space group. The large calculated band gap (ΔEg) of the crystal proves it is stable, which is consistent with the conclusion from gas phase. The conduction band (LUCO) is mainly contributed from the p state of N atom and valence band (HOCO) from the p state of F atom. [ABSTRACT FROM AUTHOR]

Studies have suggested that octanitrocubane (ONC) is one of the most powerful non- nuclear high energy density material (HEDM) currently known. 2,4,6,8-Tetranitro- 1,3,5,7-tetraazacubane (TNTAC) studied in this work may also be a novel HEDM due to its high nitrogen content and crystal density. Density functional theory and molecular mechanics methods have been employed to study the crystal structure, IR spectrum, electronic structure, thermodynamic properties, gas-phase and condensed-phase heat of formation, detonation performance, and pyrolysis mechanism of TNTAC. The TNTAC has a predicted density of about 2.12 g/cm³, and its detonation velocity (10.42 km/s) and detonation pressure (52.82 GPa) are higher than that of ONC. The crystalline packing is P212121, and the corresponding cell parameters are Z = 4, a = 8.87 Å, b = 8.87 Å, and c = 11.47 Å. Both the density of states of the predicted crystal and the bond dissociation energy of the molecule in gas phase show that the cage C-N bond is the trigger bond during thermolysis. The activation energy of the pyrolysis initiation reaction obtained from the B3LYP/6-311++G(2df,2p) level is 125.98 kJ/mol, which indicates that TNTAC meets the thermal stability request as an exploitable HEDM. [ABSTRACT FROM AUTHOR]

Three adducts SF4·BF3, SF4·AsF5, and SF4·SbF5 were studied in this work, in gas phase, DFT method was performed to study their molecular structures and thermodynamic properties. The heat of formation was studied at the high level DFT levels. Crystal structures were predicted using the Dreiding force field and refined by DFT-GGA-RPBE method. All the obtained crystal structures belong to the P21/c space group. The lattice energies were predicted to be located between -91.86 and -693.73 kJ/mol at the GGA-RPBE level. Based on the optimized crystal structures, the band gap (ΔEg) and density of state (DOS) were predicted and the calculations indicate that they are semiconductors with the band gap between 2.22 and 2.43 ev. [ABSTRACT FROM AUTHOR]