[en] Highlights: • A simple lattice energy calculation technique is introduced. • We obtained a good agreement with experimental data. • Calculated percentage deviation values are between %1 to 2. - Abstract: Lattice energy, which is a measure of the stabilities of inorganic ionic solids, is the energy required to decompose a solid into its constituent independent gaseous ions. In the present work, the relationships between lattice energies of many diatomic and triatomic inorganic ionic solids are revealed and a simple rule that can be used for the prediction of the lattice energies of inorganic ionic solids is introduced. According to this rule, the lattice energy of an AB molecule can be predicted with the help of the lattice energies of AX, BY and XY molecules in agreement with the experimental data. This rule is valid for not only diatomic molecules but also triatomic molecules. The lattice energy equations proposed in this rule provides compatible results with previously published lattice energy equations by Jenkins, Kaya, Born-Lande, Born-Mayer, Kapustinskii and Reddy. For a large set of tested molecules, calculated percent standard deviation values considering experimental data and the results of the equations proposed in this work are in general between %1–2%.

[en] Highlights: • Hydration enthalpies are calculated from ion absolute hardness for +1 and −1 ions. • To d block cations (Cu⁺, Ag⁺ and Au⁺): Δ_hydH^o = −(9.645 η⁺ + 245.930) (Z_eff/(n − 1)), where n is the main quantum number for the valence electron. • A typical VBT parameter (V_m^−1/3) is related with η⁺ and η⁻ values. That is, is stablished a direct relationship between a structural parameter available by X-ray data and the energy of atomic/molecular orbitals. In the present work, absolute hydration enthalpies are calculated from ion absolute hardness for a series of +1 and −1 ions. The calculated values are compared with those previously reported (Housecroft, 2017) [2] and relationships between V_m^−1/3 and absolute hardness are stablished. The following empirical equations have been derived, for cations and anions, respectively: Δ_hydH^o = −(9.645 η⁺ + 245.930) and Δ_hydH^o = −(64.601 η⁻ + 12.321). In such equations, η⁺ and η⁻ are the absolute hardness. It is shown that for d block monocations (Cu⁺, Ag⁺ and Au⁺), hydration enthalpy is closely related with Clementi effective nuclear charge by the equation: Δ_hydH^o = −(9.645 η⁺ + 245.930) (Z_eff/(n − 1)), where n is the main quantum number. Furthermore, is shown that a typical VBT parameter (V_m^−1/3) is related with η⁺ and η⁻ values and so, with the energies of the frontier orbitals, that is, is stablished a direct relationship between a structural parameter available by X-ray data and the energy of atomic/molecular orbitals.

[en] Highlights: • The inhibition performance of three Schiff bases on steel were studied theoretically. • The adsorption energies of the Schiff bases with Fe (110) were high and negative. • BDTC adsorbed more stronger on Fe than BMTC and BHTC. • DFT modeling and Monte Carlo simulations provided molecular level insights. • Theoreical evaluation and experimental results were in good agreement. DFT and Monte Carlo simulation were performed on three Schiff bases namely, 4-(4-bromophenyl)-N^′-(4-methoxybenzylidene)thiazole-2-carbohydrazide (BMTC), 4-(4-bromophenyl)-N^′-(2,4-dimethoxybenzylidene)thiazole-2-carbohydrazide (BDTC), 4-(4-bromophenyl)-N^′-(4-hydroxybenzylidene)thiazole-2-carbohydrazide (BHTC) recently studied as corrosion inhibitor for steel in acid medium. Electronic parameters relevant to their inhibition activity such as E_HOMO, E_LUMO, Energy gap (ΔE), hardness (η), softness ($\sigma$), the absolute electronegativity (χ), proton affinity $\left(\mathrm{PA}\right)$ and nucleophilicity (ω) etc., were computed and discussed. Monte Carlo simulations were applied to search for the most stable configuration and adsorption energies for the interaction of the inhibitors with Fe (110) surface. The theoretical data obtained are in most cases in agreement with experimental results.

[en] In this pure theoretical study, a hitherto unexplored equation based on Shannon radii of the ions forming that crystal and chemical hardness of any crystal to calculate the lattice energies of simple inorganic ionic crystals has been presented. To prove the credibility of this equation, the results of the equation have been compared with experimental outcome obtained from Born-Fajans-Haber- cycle which is fundamentally enthalpy-based thermochemical cycle and prevalent theoretical approaches proposed for the calculation of lattice energies of ionic compounds. The results obtained and the comparisons made have demonstrated that the new equation is more useful compared to other theoretical approaches and allows to exceptionally accurate calculation of lattice energies of inorganic ionic crystals without doing any complex calculations.

[en] The maximum hardness (MHP) and minimum polarizability (MPP) principles have been analyzed using the relationship among the lattice energies of ionic compounds with their electronegativities, chemical hardnesses and electrophilicities. Lattice energy, electronegativity, chemical hardness and electrophilicity values of ionic compounds considered in the present study have been calculated using new equations derived by some of the authors in recent years. For 4 simple reactions, the changes of the hardness (Δη), polarizability (Δα) and electrophilicity index (Δω) were calculated. It is shown that the maximum hardness principle is obeyed by all chemical reactions but minimum polarizability principles and minimum electrophilicity principle are not valid for all reactions. We also proposed simple methods to compute the percentage of ionic characters and inter nuclear distances of ionic compounds. Comparative studies with experimental sets of data reveal that the proposed methods of computation of the percentage of ionic characters and inter nuclear distances of ionic compounds are valid.

[en] Highlights: • We obtained the habit information of α-Fe obtained by the “Morphology” module. • The adsorption of pyrrole, furan, and thiophene on Fe(110) surface were studied by DFT calculations. • Our DFT modeling provided a reasonable micro-explanation to the empirical rule. - Abstract: Steel is an important material in industry. Adding heterocyclic organic compounds have proved to be very efficient for steel protection. There exists an empirical rule that the general trend in the inhibition efficiencies of molecules containing heteroatoms is such that O < N < S. However, an atomic-level insight into the inhibition mechanism is still lacked. Thus, in this work, density functional theory calculations was used to investigate the adsorption of three typical heterocyclic molecules, i.e., pyrrole, furan, and thiophene, on Fe(110) surface. The approach is illustrated by carrying out geometric optimization of inhibitors on the stable and most exposed plane of α-Fe. Some salient features such as charge density difference, changes of work function, density of states were detailedly described. The present study is helpful to understand the afore-mentioned experiment rule.

[en] Highlights: • TGETET/DAH and TGETET/DDM curing epoxy resins were investigated as potential anticorrosive coatings. • TGETET/DAH and TGETET/DDM tested present higher protective efficiencies (for EIS and PC) compared with 3.5% NaCl solution only. • SEM analysis showed that the TGETET/DAH and TGETET/DDM could effectively block the Cl^- ions attack by chemisorption on the CS surface. • HF, MDs and experimental data lead to used TGETET/DAH and TGETET/DDM as potential anticorrosive coatings for CS in NaCl medium. Triglycidyl ether triethoxy triazine (TGETET) epoxy resin cured by 1.6-diaminohexane (TGETET/DAH) and 4.4-diaminodiphenyl methane (TGETET/DDM) was investigated as potential anticorrosive coating for carbon steel in sodium chloride medium. Polarization curves (PC) and electrochemical impedance spectroscopy (EIS) results displayed the protective efficiency of TGETET/DDM is higher than that of TGETET/DAH in 3.5 %NaCl medium. SEM data showed that both TGETET/DAH and TGETET/DDM could be significantly stopped the chloride ions attack due to adhesion between the protective layer formed on CS coated. Chemical reactivity tendency of TGETET/DAH and TGETET/DDM compounds were evaluated using global quantum chemical descriptors (GQCDs) and molecular dynamics simulation (MDs).