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Supramolecular helices that arise from the self-assembly of small organic molecules via non-covalent interactions play an important role in the structure and properties of the corresponding materials. Here we study the supramolecular helical aggregation of oligo(phenyleneethynylene) monomers from a theoretical point of view, always guiding the studies with experimentally available data. In this way, by systematically increasing the number of monomer units, optimized n-mer geometries are obtained along with the corresponding absorption and circular dichroism spectra. For the geometry optimizations we use density functional theory together with the B3LYP-D3 functional and the 6–31G** basis set. For obtaining the spectra we resort to time-dependent density functional theory using the CAM-B3LYP functional and the 3–21G basis set. These combinations of density functional and basis set were selected after systematic convergence studies. The theoretical results are analyzed and compared to the experimentally available spectra, observing a good agreement.

Dispersion and electrostatic interactions both contribute significantly to the tight assembly of macromolecular chains within crystalline polysaccharides. Using dispersion-corrected density functional theory (DFT) calculation, we estimated the elastic tensor of the four crystalline cellulose allomorphs whose crystal structures that are hitherto available, namely, cellulose Iα, Iβ, II, IIII. Comparison between calculations with and without dispersion correction allows quantification of the exact contribution of dispersion to stiffness at molecular level.

Doping silicon wafers without using highly toxic or corrosive chemical substances has become a critical issue for semiconductor device manufacturing. In this work, ultra‐thin films of hydroxyapatite (Ca5(PO4)3OH) are prepared by tethering by aggregation and growth (T‐BAG), and further processed by spike annealing. Via in situ infrared (IR), the decomposition of hydroxyapatite and intermixing with the native silicon oxide is observed already at temperatures as low as 200 °C. Phosphate transport through the native silicon oxide is driven by a phase transformation into a more stable thermal oxide. At 700 °C, diffusion of phosphorus into the sub‐surface region of oxide‐free silicon is observed. In situ IR combined with electrical impedance spectroscopy (EIS), time‐of‐flight secondary ion mass spectrometry (ToF‐SIMS), and X‐ray photoelectron spectroscopy (XPS) measurements allows to conclude that the phosphorus is: i) transported through the silicon oxide barrier, ii)) diffused inside the oxide‐free silicon, and iii) finally modified the electrical activity of the silicon wafer. To further explain the experimental findings, density‐functional theory (DFT) is used to demonstrate the extent of the effect of phosphorus doping on the electronic nature of silicon surfaces, showing that even small amounts of doping can have a measurable effect on the electrical performance of semiconductor wafers. Doping silicon wafers without using highly toxic or corrosive chemical substances is a critical issue for semiconductor device manufacturing. Peter Thissen and Roberto C. Longo investigate thin mineral layers of hydroxyapatite as a doping basis. Measurements show that the phosphorus is transported through the silicon oxide barrier, then diffuses inside the oxide‐free silicon and finally changes the electrical activity.

The entry of the SARS-CoV-2, a causative agent of COVID-19, into human host cells is mediated by the SARS-CoV-2 spike (S) glycoprotein, which critically depends on the formation of complexes involving the spike protein receptor-binding domain (RBD) and the human cellular membrane receptor angiotensin-converting enzyme 2 (hACE2). Using classical site density functional theory (SDFT) and structural bioinformatics methods, we investigate binding and conformational properties of these complexes and study the overlooked role of water-mediated interactions. Analysis of the three-dimensional reference interaction site model (3DRISM) of SDFT indicates that water mediated interactions in the form of additional water bridges strongly increases the binding between SARS-CoV-2 spike protein and hACE2 compared to SARS-CoV-1-hACE2 complex. By analyzing structures of SARS-CoV-2 and SARS-CoV-1, we find that the homotrimer SARS-CoV-2 S receptor-binding domain (RBD) has expanded in size, indicating large conformational change relative to SARS-CoV-1 S protein. Protomer with the up-conformational form of RBD, which binds with hACE2, exhibits stronger intermolecular interactions at the RBD-ACE2 interface, with differential distributions and the inclusion of specific H-bonds in the CoV-2 complex. Further interface analysis has shown that interfacial water promotes and stabilizes the formation of CoV-2/hACE2 complex. This interaction causes a significant structural rigidification of the spike protein, favoring proteolytic processing of the S protein for the fusion of the viral and cellular membrane. Moreover, conformational dynamics simulations of RBD motions in SARS-CoV-2 and SARS-CoV-1 point to the role in modification of the RBD dynamics and their impact on infectivity.

The energetics and atomic structure associated with the localized hole formed near an Al-atom dopant in α-quartz are calculated using a variational, self-consistent implementation of the Perdew–Zunger self-interaction correction with complex optimal orbitals. This system has become an important test problem for theoretical methodology since generalized gradient approximation energy functionals, as well as commonly used hybrid functionals, fail to produce a sufficiently localized hole due to the self-interaction error inherent in practical implementations of Kohn–Sham density functional theory. The self-interaction corrected calculations are found to give accurate results for the energy of the defect state with respect to both valence and conduction band edges as well as the experimentally determined atomic structure where only a single Al–O bond is lengthened by 11%. The HSE hybrid functional, as well as the PW91 generalized gradient approximation functional, however, gives too small an energy gap between the defect state and the valence band edge, overly delocalized spin density and lengthening of more than one Al–O bond.

In this work, we present a computational investigation on the photoexcitation of indigo carmine (IC). Physical insights regarding IC photoexcitation and photolysis were obtained from a fundamental perspective through quantum chemistry computations. Density functional theory (DFT) was used to investigate the ground state while its time-dependent formalism (TD-DFT) was used for probing excited state properties, such as vertical excitation energies, generalized oscillator strengths (GOS), and structures. All the computations were undertaken using two different approaches: M06-2X/6-311+G(d,p) and CAM-B3LYP/6-311+G(d,p), in water. Results determined using both methods are in systematic agreement. For instance, the first singlet excited state was found at 2.28 eV (with GOS = 0.4730) and 2.19 eV (GOS = 0.4695) at the TD-DFT/CAM-B3LYP/6-311+G(d,p) and TD-DFT/M06-2X/6-311+G(d,p) levels of theory, respectively. Excellent agreement was observed between the computed and the corresponding experimental UV-Vis spectra. Moreover, results suggest IC undergoes photodecomposition through excited state chemical reaction rather than via a direct photolysis path. To the best of our knowledge, this work is the first to tackle the photoexcitation, and its potential connections to photodegradation, of IC from a fundamental chemical perspective, being presented with expectations to motivate further studies.

It is still a grand challenge to develop a highly efficient nonprecious-metal electrocatalyst to replace the Pt-based catalysts for oxygen reduction reaction (ORR). Here, we propose a surfactant-assisted method to synthesize single-atom iron catalysts (SA-Fe/NG). The halfwave potential of SA-Fe/NG is only 30 mV less than 20% Pt/C in acidic medium, while it is 30 mV superior to 20% Pt/C in alkaline medium. Moreover, SA-Fe/NG shows extremely high stability with only 12 mV and 15 mV negative shifts after 5,000 cycles in acidic and alkaline media, respectively. Impressively, the SA-Fe/NG-based acidic proton exchange membrane fuel cell (PEMFC) exhibits a high power density of 823 mW cm−2. Combining experimental results and density-functional theory (DFT) calculations, we further reveal that the origin of high-ORR activity of SA-Fe/NG is from the Fe-pyrrolic-N species, because such molecular incorporation is the key, leading to the active site increase in an order of magnitude which successfully clarifies the bottleneck puzzle of why a small amount of iron in the SA-Fe catalysts can exhibit extremely superior ORR activity.

Increases in synthetic drug production and distribution pose significant risks to public health and safety. Traditional detection methods often fail to accurately identify these complex chemicals, particularly when they are mixed. Accordingly, Herein, an advanced density functional theory spectroscopy integrated identification method (D‐SIIM) comprising a combination of experimental and theoretical analyses is introduced. D‐SIIM is helpful in correcting the erroneous information provided by gas chromatography–mass spectrometry during the analysis of a mixture of three synthetic drug stimulants. Furthermore, the application of a denoising mechanism to the experimental Raman data considerably aligns experimental results with theoretical predictions, thereby augmenting the accuracy and reliability of D‐SIIM. Moreover, the potential of employing hyperpolarized nuclear magnetic resonance (NMR) spectroscopy to enhance NMR signals at low concentrations is explored. Current approach provides a robust and adaptable framework for identifying synthetic drugs in complex mixtures and will play critical roles in forensic investigations and drug enforcement strategies. A novel approach integrates gas chromatography‐mass spectrometry with infrared, Raman, and nuclear magnetic resonance spectroscopy plus density functional theory to detect synthetic drugs. Quantum hyperpolarization further boosts NMR sensitivity for low‐concentration samples, improving detection accuracy in complex mixtures and offering promising forensic applications.

We report a theoretical investigation of the influence of Cu doping into TiO2 with various concentrations on crystal structure, stability, electronic structures and optical absorption coefficient using density functional theory via the hybrid formalism based on Heyd Scuseria Ernzerhof. Our findings show that oxygen-rich environments are better for fabricating Cu-doped materials and that the energy of formation for Cu doping at the Ti site is lower than for Cu doping at the O site under these environments. It is found that Cu doping introduces intermediate bands into TiO2, narrowing the band gap. Optical absorption curves show that the Cu-doped TiO2 can successfully harvest visible light. The presence of widely intermediate bands above the valence-band edge could explain the increase in the visible light absorption range. However, the intensity of visible light absorption rises with the increase in doping concentration.

The appropriate catalysts can accelerate the reaction rate and effectively boost the efficient conversion of various molecules, which is of great importance in the study of chemistry, chemical industry, energy, materials and environmental science. Therefore, efficient, environmentally friendly, and easy to operate synthesis methods have been used to prepare various types of catalysts. Although previous studies have reported the synthesis and characterization of the aforementioned catalysts, more still remain in trial and error methods, without in-depth consideration and improvement of traditional synthesis methods. Here, we comprehensively summarize and compare the preparation methods of the trial-and-error synthesis strategy, structure-activity relationships and density functional theory (DFT) guided catalysts rational design for nanomaterials and atomically dispersed catalysts. We also discuss in detail the utilization of the nanomaterials and single atom catalysts for converting small molecules (H 2 O, O 2 , CO 2 , N 2 , etc.) into value-added products driven by electrocatalysis, photocatalysis, and thermocatalysis. Finally, the challenges and outlooks of mass preparation and production of efficient and green catalysts through conventional trial and error synthesis and DFT theory are featured in accordance with its current development.