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Aluminum oxide (Al₂O₃) is a widely used ceramic material known for its high-temperature stability, which makes it valuable in a variety of industrial applications. The conversion from bulk to surface modification may lead to substantial changes in their thermodynamic properties. Consequently, this study endeavors to resolve the primary thermodynamic properties of Al₂O₃ by employing DFT calculation. The FP-LAPW+lo method is first used in the WIEN2K software to determine the surface of bulk Al₂O₃ with varying thicknesses. The thermodynamic parameters of Al₂O₃ at high pressure and elevated temperature, such as bulk modulus, thermal expansion coefficient, heat capacity, entropy, enthalpy and Debye temperature are investigated with the help of the quasi-harmonic Debye model in the Gibbs2 package. The calculated thermodynamic parameters of the Al₂O₃ agree with earlier findings. The results reveal that with increasing thickness, the thermal expansion coefficient and entropy decrease while the enthalpy increases, indicating that Al₂O₃ can be a suitable candidate for various energy and electronic industrial applications.

In this study, we investigate the properties of double perovskite compounds K₂CuBiBr₆ and K₂AgBiBr₆ using density functional theory and semi-classical Boltzmann transport theory. Our goal is to identify materials optimized for optoelectronic and thermoelectric applications. The electronic property analysis shows that K₂CuBiBr₆ and K₂AgBiBr₆ exhibit semiconductor behavior, with indirect bandgap values of 1.73eV and 2.83eV, respectively. The compounds’ energetic and structural stability is demonstrated by their tolerance factor values and negative formation and cohesive energies. Moreover, full compliance with the Born elastic stability criteria confirms their resilience to deformation. The optical properties, including dielectric function, absorption coefficient, reflectivity, and refractive index, reveal high absorption coefficients exceeding $1.7\times 10^5{\mathrm{\text{cm}}}^{-1}$ in the visible range and over $7\times 10^5$cm${}^{-1}$ in the near-UV region. Their low reflectivity, around 20% in the visible spectrum, results in a notable improvement in light absorption, thus significantly increasing the efficiency of light-to-electricity conversion, which is highly beneficial for photovoltaic cells. High Seebeck coefficients, electrical conductivity, and merit factor make these materials promising candidates for thermoelectric power generation and cooling applications.

Structural, electronic, and vibrational properties of magnesium diboride have been investigated by performing ab initio calculation within DFT level considering full MP2 correlation correction through B3LYP exchange-correlation functional. The structural, electronic, and vibrational properties of MgB₂ triatom have been calculated in its ground state.

Dansyl chloride (DNS-Cl) is a fluorescence-labeled organic compound widely used in fields such as pharmacology, toxicology, organic synthesis and biochemistry. We perform a computational study of the structural, electronic, optical and vibrational properties of its orthorhombic crystalline form. We use the pseudopotential approach of the density functional theory (DFT) considering the generalized gradient approximation with dispersion correction (GGA+TS), the local density approximation (LDA) and the hybrid exchange-correlation functional HSE06. The band structure shows a direct gap in all approaches. Optical properties are calculated considering polarization along the polycrystal direction with the main features correlated to the band structure. Further, vibration modes, infrared (IR) and Raman spectra are also obtained and analyzed.

Present study is a computational approach focused on optical properties of Ni-doped rocksalt CdS system under PBE-GGA and GGA + U approximations. Investigation of optical properties of CdS:Ni system by fixing supercell size and increasing dopant concentration is a focus of study. Cd atoms are substituted by Ni atoms and optical properties show significant change for higher Ni concentration. Redshift in optical absorption is observed as dopant concentration is increased. Interaction of Ni and S atoms and localization of d-states are inspected near the conduction band minima or Fermi surface. GGA + U absorption plots show slight variation with increase in energy values. Ni-doping in CdS host lattice enhances its opto-electronic properties which extend its applications in optical sensors, optical and similar devices.

For novel $\gamma$-Si₃Sb₄, pseudocubic-Si₃Sb₄, cubic-Si₃Sb₄ and $t$-Si₃Sb₄, the structural, elastic and electronic properties are investigated using first-principles density functional theory (DFT). The elastic constants and phonon dispersion spectra show that they are mechanically and dynamically stable. The bulk moduli, shear moduli, Young’s moduli, Poisson’s ratios and Pugh ratios for the four compounds have been calculated. The bulk moduli indicate that the bond strength of $\gamma$-Si₃Sb₄ is stronger than others. The values of the Poisson’s ratios and Pugh ratios show that pseudocubic-Si₃Sb₄ is the stiffest among the four Si₃Sb₄ compounds. Tetragonal Si₃Sb₄ are more brittle than cubic Si₃Sb₄. For the four Si₃Sb₄ compounds, the elastic anisotropies are analyzed via the anisotropic indexes and the 3D surface constructions. The $\gamma$-Si₃Sb₄ elastic anisotropy is stronger than others and the $t$-Si₃Sb₄ is weaker than others. The calculated band structures show that they exhibit metallic features. The results of their TDOS show that there are many similarities. The peaks of TDOS are derived from the contributions of Si “s”, Si “p”, Sb “s” and Sb “p” states.

In this work, we study the impact of the external electric field $(E_{\mathrm{\text{ext}}})$ on graphene oxide (GO) layer to improve and optimize its electronic and optical properties, as a result to enhance optoelectronic device technology applications. A three-dimensional $E_{\mathrm{\text{ext}}}$ applied on GO will be examined using the density functional theory (DFT). The $E_{\mathrm{\text{ext}}}$ causes significant modifications to the electronic and optical properties of GO. When increasing the $E_{\mathrm{\text{ext}}}$, a global increase is noted in the bandgap in the x- and y-directions. As for the z-direction, the bandgap energy of GO decreases for an increasing $E_{\mathrm{\text{ext}}}$. The absorption coefficient ($\alpha$) peaks intensities decreased in both visible and ultraviolet (UV) ranges by the effect of the $E_{\mathrm{\text{ext}}}$ applied in the x-direction, and were increased when the $E_{\mathrm{\text{ext}}}$ is applied in the y- and z-directions. It was found that, the electronic and optical properties of GO material, could be controlled by the effects of the $E_{\mathrm{\text{ext}}}$ and by its direction.

Electronic structure calculations of all 10 unique base pair (bp) steps have been calculated to study the interaction energies of the bp steps, density of states (DOS), projected density of states (pDOS) using the density functional theory (DFT). Plane wave basis with ultrasoft pseudo-potential method has been used within the local density approximation (LDA) for the exchange correlation functional. Electron densities of the bp steps corresponding to HOMO and LUMO level have been calculated to understand the difference in stacking energies of the bp steps. The variation of HOMO–LUMO gap (g) of all possible bp steps on twist angle has been studied. We have observed that out of the 10 bp steps, 4 purine–purine bp steps (d(AA), d(GG), d(AG) and d(GA)), show significant variation of $g$ on twist angle. The observed variation on twist angle of d(AA) bp step has been explained by the calculated DOS and electron densities.

The density functional theory has been used to study the adsorption performance of polluting Cu${}^{2+}$ and Zn${}^{2+}$ ions on defective graphene. Compared to intrinsic graphene, the adsorption distance between defective graphene and Cu${}^{2+}$/Zn${}^{2+}$ decreases greatly, and the adsorption energy and charge transfer amount increases significantly. The calculation of charge density demonstrates that clear hybridization happens between defective graphene and Cu${}^{2+}$/Zn${}^{2+}$ ions, suggesting the formation of chemical adsorption. The frontier orbit analysis shows that defective graphene has greater electrical sensitivity after adsorbing Cu${}^{2+}$/Zn${}^{2+}$ ions. Therefore, defective graphene could be a potential material for the treatment of contaminating heavy metal ions.

Calculations of chemical reactions between C₂₀, C₆₀, hydrogen and water molecules are carried out using the PM3 method. Reactions with a hydrogen release at room temperature and atmospheric pressure are identified by the Gibbs energy change. The hydrogen release can be raised by increasing the number of water molecules in chlorine-assisted decomposition of fullerenes. Calculations of the Gibbs energy of chemical reactions involving water molecules between two parallel curved graphene sheets are carried out using DFT with the functional UB3LYP. During pumping between plates of an electric capacitor designed from curved graphene sheets, the water vapor with the assistance of external illumination is enriched by electrically neutral hydroxyl groups (OH)⁰.

The quantitative structure–activity relationship (QSAR) of troxacitabine prodrugs with antitumor activity has been studied by using the density functional theory (DFT), molecular mechanics (MM2), and statistical methods. The established QSAR model shows not only significant statistical quality, but also predictive ability, with the square of adjusted correlation coefficient and the square of the cross-validation coefficient (q² = 0.807). The antitumor activity is expressed as pIC₅₀, which is defined as the negative value of the logarithm of necessary molar concentration of a compound to cause 50% growth inhibition against the human non-small-cell lung cancer cell line SW1573. It appears to be mainly governed by two factors (or original variables), i.e. the calculated hydrophobic coefficient (C log P) of whole molecule and the net charges of the first atom of substituent R (Q_FR), although three descriptors, i.e. C log P, (C log P)², and Q_FR, were selected in our multiple linear regression model. The factor C log P shows parabolic relation to pIC₅₀ and its suitable range is around 5.6, and the other factor Q_FR shows a significant negative correlation with pIC₅₀. In this paper, a detailed discussion on these two factors was carried out, and their close correlation with the action mechanism of these prodrugs was reasonably revealed. Such results can offer some useful theoretical references for understanding the action mechanism and directing the molecular design of this kind of compound with antitumor activity.

Two-dimensional (2D) and three-dimensional (3D) quantitative structure–activity relationships (QSARs) of 23 analogs of 2-Methoxyestradiol with anticancer activity (expressed as pGI₅₀) against MCF-7 human breast cancer cells have been studied by using a combined method of the DFT, MM2 and statistics for 2D, as well as the comparative molecular field analysis (CoMFA) for 3D. The established 2D-QSAR model in training set shows not only significant statistical quality, but also predictive ability, with the square of adjusted correlation coefficient and the square of the cross-validation coefficient (q² = 0.779). The same model was further applied to predict pGI₅₀ values of the four compounds in the test set, and the resulting being as high as 0.827, further confirms that this 2D-QSAR model has high predictive ability for this kind of compound. The 3D-QSAR model also shows good correlative and predictive capabilities in terms of R²(0.927) and q²(0.786) obtained from CoMFA model. The results that 2D- and 3D-QSAR analyses accord with each other, suggest that the electrostatic interaction plays a decisive role in determining the anticancer activity of the studied compounds, and that increasing the negative charge of substituent R₂ and the positive charge of substituents linking to C₁₇ as well as decreasing the size of substituent R₁ are advantageous to improving the cytotoxicity. Such results can offer some useful theoretical references for directing the molecular design and understanding the action mechanism of this kind of compound with anticancer activity.

The gas-phase metal affinities of histidine Li⁺, Na⁺ and K⁺ ions have been determined theoretically employing the hybrid B3LYP exchange–correlation functional and using 6-311++G** basis sets. All computations indicate that the metal ion affinity decreases on going from Li⁺ to Na⁺ and K⁺ for the considered amino acid. Different types of M⁺ coordinations on several histidine conformers/tautomers were considered in detail.

The optimized structures indicate that Li⁺ and Na⁺ prefer a tri-dentate coordination, bonding with a nitrogen atom of imidazole ring (N^τ), –NH₂, and an oxygen atom of a carbonyl, while in the K⁺-histidine lowest-energy conformer, the cation appears to be bi-coordinated to both oxygen atoms of the zwitterionic form by the energy values not too far from that of tri-coordination. We also performed the DFT calculations for proton dissociation energy of histidine both in the presence and absence of alkali metal ions. Our results also reveal that the acidity of histidine dramatically increases upon metal ion complexation.

A molecular recognition mechanism based on dimeric model for cyclic dipeptide Cyclo[(S)-His-(S)-Phe] (abridged CHP) catalyzed autoinduction is proposed according to the inference of previous experimental findings, which is supported by theoretical calculation with Oniom(B3LYP/3-21G*:AM1) method. The most unstable CHP dimer whose intermolecular hydrogen bonds are immensely lessened by two intramolecular hydrogen bonds is defined as the highest active component (IIa) existing in solid among the three possible dimers (Ia, IIa, and IIb). The carbonyl group of benzaldehyde coordinates to CHP dimer (IIa) by a hydrogen bond with Phe–N_αH rather than His–N_αH and HCN interacted with the imidazole moiety of His residue to form cyanide ion. In view of the theoretical calculation and experimental results, the structures of the nine-ring complexes derived from interaction between catalytic active dimer CHP(IIa) and cyanohydrins were postulated to explain the enantioselective autoinduction: The structure of no nitrile involved six-ring complex derived from interaction between catalytic active dimer CHP(IIa) and cyanohydrins were postulated to explain the elimination of enantioselective autoinduction.

The extensive search for the global minimum structure of at the B3LYP/LANL2DZ level of the theory revealed that is the ground state. Molecular orbital (MO) analysis reveal that delocalized partial σ and δ bonding in makes partial (σ- and δ-) aromaticity. The multiple d-orbital aromaticities are responsible for a three-center metal–metal bond of the triangular Re₃. We also search the pyramidal Re₃Li²⁺, Re₃X³⁺ (X = Be, Mg and Ca) and Re₃Y (Y = Al and Ga) clusters containing to reveal that the was preserved perfectly in all-metal compounds, which also possess partially σ- and δ-multiple aromatic characters.

The electronic structures and stabilities of all benzenoid (enol) and quinonoid (keto) forms of 4-hydroxynaphthaldehyde (ALD-14) have been investigated using density functional theory (DFT) with a range of functionals and basis sets. The anti-enol form represents the global minimum energy structure. Low rotation barriers of both the hydroxyl and the aldehyde groups characterize this form. Fourier analysis of the potential energy function for rotation indicate that the conformational preference of ALD-14 is determined by both the dipole–dipole repulsion and bond moments interactions. Further, three different ALD-14 dimer complexes are investigated, i.e. head-to-tail (HT), head-to-head (HH), and stacked (S) forms. The analysis of natural bond order, quantum topology features of the Laplacian of the electron density, binding energies and structural parameters of these dimers point to comparable stabilities of the HT and S-dimers, with a preference for a stacking contact. The origin of its stability can be traced to π-conjugative, H-bonding and dispersion interactions.

The hydrogen bonding interactions between letrozole (Let) anticancer drug and three copolymers of methacrylic acid-trimethylolpropane trimethacrylate (M1–M3 as molecular imprinted polymers) were studied using density functional theory (DFT) at both B3LYP and B3PW91 levels. The binding energies were corrected for the basis set superposition error (BSSE) and zero-point vibrational energies (ZPVE) so that the most negative $\mathrm{\Delta }{E}_{\mathrm{\text{binding}}}$ were measured for compounds 7 and 8 formed between M1 copolymer and endocyclic N1 and N2 atoms of drug, respectively. Also, among complexes 13–15 in which two copolymers were contributed in the formation of O–H$\dots$N bonds with the drug, compound 13 (containing two M1 copolymers) showed the highest $\mathrm{\Delta }{E}_{\mathrm{\text{binding}}}$ value. The interactions of all copolymers with drug were exergonic (spontaneous interaction) and exothermic. The QTAIM data supported the covalent character of the C–N, C–H, N–N, C–O, O–H and O–H$\dots$N bonds, the intermediate nature of C$\equiv$N and C$=$O bonds while the electrostatic character of C–H$\dots$O, HC$\dots$HC and CH$\dots$N interactions. According to the $\mathrm{\Delta }{E}_{\mathrm{\text{binding}}}$, $\mathrm{\Delta }{G}_{\mathrm{\text{interaction}}}$ and $\mathrm{\Delta }{H}_{\mathrm{\text{interaction}}}$ values, it was suggested that t complexes 7 and 8 (among two particles systems) as well as complex 13 (among three particles systems) can be the most promising drug delivery systems.

In this study, mechanism and stereochemistry of four-component Ugi reaction was investigated theoretically. Structures of reagents, products, intermediates, and transition states were optimized at B3LYP/6-31$+$G(d,p) level of theory. Mechanism and stereoselectivity of the reaction depended on several processes, including bond rotation, ring closure ring opening, acid-base, nucleophile-electrophile competitions, and rearrangements. These diverse phenomena were studied to provide a clearer picture of the mechanism of this valuable reaction, especially in terms of stereochemistry considerations. According to the results, (E)-oxazolidinols were considered as proper intermediates in Ugi reaction mechanism. In addition, the key point of diastereoselectivity of the reaction was under kinetic and thermodynamic controls of nucleophilic attack of isocyanide to less hindered re-face (E${}_{\mathrm{\text{a}}}=7.31$ compared to 10.19kcal/mol for si-face) of chiral (E)-iminium ion.

In this study, mechanism and stereochemistry of multicomponent domino Knoevenagel/Diels–Alder reaction were investigated theoretically. Structures of reagents, transition states, intermediates, and products were optimized at M062X/6-31$+$G(d,p) level of theory. Although the mechanism of this reaction involved several processes, including bond rotation, isomerization, asymmetric cycloaddition, acid-base, and nucleophile–electrophile competitions, critical processes were studied to provide a clearer picture of the mechanism of this valuable reaction in terms of stereochemistry considerations. According to the results, the ring closure step of reaction performed via a polar Dield-Alder mechanism, having enthalpy at approximately 40kcal/mol. The diastereoselectivity of the reaction was controlled by the interaction of dienophile with the less hindered face of diene through a more stable endo transition state ($\mathrm{\Delta }{G}^{\#}=23.21$ and 27.31 in methanol and gas phase, respectively). HSAB criteria could explain the regioselectivity of this reaction by considering the least softness difference ($\mathrm{\Delta }S$) for interacting C-atoms based on Hirshfeld populations. The result was the creation of cis-spiro cyclohexanone under kinetic and thermodynamic controls as a predominant diastereoselective and regioselective product.

The single crystal X-ray structure of [Co(TPP)(BzNH₂)₂](SCN), compound 2, where TPP = 5,10,15,20-tetraphenylporphyrin dianion and BzNH₂ = benzylamine, reveals that the SCN^- ion is hydrogen-bonded to one of the coordinated amino group hydrogen atoms via its sulfur atom. Furthermore, the N–H⋯SCN interaction is balanced by a stronger N–H⋯NCS hydrogen bonding interaction for the trans BzNH₂ ligand as a result of the multiple hydrogen bond accepting character of the thiocyanate ion. Analysis of the crystal packing shows that these two hydrogen bonds play a major role in fixing unusual orientations for the axial ligands relative to the porphyrin ring in this system. This, in turn, leads to the formation of a nonplanar porphyrin core conformation that is a mixture of ruffle- and saddle-type distortions. The intricate hydrogen bonding between the cations and anions in 2 results in an unusually long mean Co–N_amine coordination distance of 2.033(4) Å, some 0.05 Å longer than previously observed for other bis(primary amine) complexes of Co(III) porphyrins with comparable porphyrin ligands. Density functional theory (DFT) calculations at the B3LYP/LACVP* level of theory have been used to gauge the perturbation of the electronic structure of the [Co(TPP)(BzNH₂)₂]⁺ cation caused by the N–H⋯SCN and N–H⋯NCS hydrogen-bonded SCN^- ions. The calculations show that partial mixing of the anion MOs with those of the porphyrin cation lead to changes in the electron populations of the 3d orbitals of up to 0.42 e as well as more nearly tetragonal electronic symmetry for the Co(III) ion as a result of adjustments of the relative energies of the MOs with predominantly 3d character.