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In this paper, the structures and properties of (HF)nH2O (n = 1–9) clusters are studied by the combination of genetic algorithm (GA) and density functional theory(GDF) method. The structures are optimized at B3LYP/6–311++G(d,p) level. The refined energies are computed at CCSD(t)/aug-cc-pVDZ level. Infrared spectrum analysis, charge analysis, orbital analysis, and stability analysis are performed on the most stable configurations of each size. Lower-lying structures are obtained for (HF)nH2O (n = 5,6) clusters. (HF)7H2O cluster has special ability based on stability analysis. NCI analysis is conducted on the global optimal structure of all size clusters, and it is found that there are obvious hydrogen bonds in the clusters. Hydrogen bonding is an important factor in stabilizing (HF)nH2O (n = 1–9) composite clusters. The studied clusters can be divided into two categories: non-ionic clusters (HF)nH2O (n = 1–5) and ionic clusters (n = 6–9). [ABSTRACT FROM AUTHOR]

Rotor dynamics plays a crucial role in the performance and safety of rotating machinery, with disk position and unbalance significantly impacting system behavior. This study investigates the dynamic characteristics of two rotor configurations: a centrally mounted unbalanced disk (Rotor05un) and an off-center unbalanced disk (Rotor025un). Using numerical simulations and Monte Carlo analysis, we examined critical speeds and orbital patterns for both configurations. Probability distributions of shaft orbital positions revealed distinct patterns for each configuration. Quantile analysis revealed approximate linear trends for Rotor025un, suggesting higher system stiffness and more predictable behavior near critical speeds. Cross-sectional analyses of the orbits provided insights into the complex interactions between disk position, gyroscopic effects, and system natural frequencies. These findings provide valuable insights for rotor system design, particularly for applications with non-ideal mass distributions. The study goes beyond traditional critical speed analysis to examine orbital patterns and point on orbit occurrence from a probabilistic perspective. Based on the simulation of the orbits, an orbital is determined that allows the probability of the shaft occurring at the analyzed distance from the origin to be determined. The paper also offers insights into the complex interaction behavior of chosen rotor configurations and highlights the importance of considering disk position in predicting and optimizing rotor dynamic behavior, contributing to the development of more robust and efficient rotating machinery. [ABSTRACT FROM AUTHOR]

The Cu−O−Cu core has been proposed as a potential site for methane oxidation in particulate methane monooxygenase. In this work, we used density functional theory (DFT) to design a mixed‐valent CuIII−O−CuII species from an experimentally known peroxo‐dicopper complex supported by N‐donor ligands containing phenolic groups. We found that the transfer of two‐protons and two‐electrons from phenolic groups to peroxo‐dicopper core takes place, which results to the formation of a bis‐μ‐hydroxo‐dicopper core. The bis‐μ‐hydroxo‐dicopper core converts to a mixed‐valent CuIII−O−CuII core with the removal of a water molecule. The orbital and spin density analyses unravel the mixed‐valent nature of CuIII−O−CuII. We further investigated the reactivity of this mixed‐valent core for aliphatic C−H hydroxylation. Our study unveiled that mixed‐valent CuIII−O−CuII core follows a hydrogen atom transfer mechanism for C−H activation. An in‐situ generated water molecule plays an important role in C−H hydroxylation by acting as a proton transfer bridge between carbon and oxygen. Furthermore, to assess the relevance of a mixed‐valent CuIII−O−CuII core, we investigated aliphatic C−H activation by a symmetrical CuII−O−CuII core. DFT results show that the mixed‐valent CuIII−O−CuII core is more reactive toward the C−H bond than the symmetrical CuII−O−CuII core. [ABSTRACT FROM AUTHOR]

Rotor dynamics plays a crucial role in the performance and safety of rotating machinery, with disk position and unbalance significantly impacting system behavior. This study investigates the dynamic characteristics of two rotor configurations: a centrally mounted unbalanced disk (Rotor05un) and an off-center unbalanced disk (Rotor025un). Using numerical simulations and Monte Carlo analysis, we examined critical speeds and orbital patterns for both configurations. Probability distributions of shaft orbital positions revealed distinct patterns for each configuration. Quantile analysis revealed approximate linear trends for Rotor025un, suggesting higher system stiffness and more predictable behavior near critical speeds. Cross-sectional analyses of the orbits provided insights into the complex interactions between disk position, gyroscopic effects, and system natural frequencies. These findings provide valuable insights for rotor system design, particularly for applications with non-ideal mass distributions. The study goes beyond traditional critical speed analysis to examine orbital patterns and point on orbit occurrence from a probabilistic perspective. Based on the simulation of the orbits, an orbital is determined that allows the probability of the shaft occurring at the analyzed distance from the origin to be determined. The paper also offers insights into the complex interaction behavior of chosen rotor configurations and highlights the importance of considering disk position in predicting and optimizing rotor dynamic behavior, contributing to the development of more robust and efficient rotating machinery.

Boron‐based compounds such as frustrated Lewis pairs and borylenes that mimic transition‐metal(TM)‐like reactivity have attracted significant interest in recent years. This work examines the reactivity of boron oxide (B2O3) towards dioxygen for methane activation. Density functional theory in combination with orbital analysis were utilized to derive mechanistic pathways for methane‐to‐formaldehyde conversion over B2O3 in presence of closed‐shell singlet and triplet O2. Multiple pathways were screened on the triplet spin state. Best route via the triplet spin state depicts the interaction of B2O3 with dioxygen (O1=O2) and CH4 at a barrier of 49.8 kcal mol−1, to produce an intermediate having a B−O1−O2H unit and a free CH3 radical, which later react together at a barrier of 57.6 kcal mol−1, to finally yield HCHO. In the singlet spin state, a free CH3 radical does not form instead an intermediate with a B−O1−O2−CH3 unit is found after crossing a barrier of 41.1 kcal mol−1, which further undergoes via a relatively lower barrier of 23.4 kcal mol−1 to yield HCHO. Thus, the singlet pathway is energetically preferred over the triplet one. Orbitals further capture that at singlet and triplet states, methane activation follows a hydride and a hydrogen‐atom‐transfer mechanism, respectively. [ABSTRACT FROM AUTHOR]

Context: The structures of Ag2n-1Sn− (n = 2–11) clusters are obtained by the combination of genetic algorithm (GA) and density functional theory (DFT). All the global minimum structures prefer hollow polyhedral structures, in which S–Ag-S element, triangular Ag3S3 and tetragonal Ag4S4 units present to stabilize the structures. The S atoms in the structures appear in μ3-S or μ4-S form. Adiabatic and vertical electron affinities of the clusters have been obtained, which reveals that they increases as cluster size. Stability analysis shows that Ag9S5− and Ag19S10− have special stability. The HOMO, LUMO orbitals of the clusters are obtained and the orbital components of them are calculated. The HOMO orbitals are mainly from the p orbitals of S atoms, whereas the s, p and d orbitals of Ag atoms contribute much bigger than the p orbitals of S atoms for LUMO orbitals. The orbital delocalization indexes (ODI) of the HOMOs and LUMOs are calculated, and the small ODIs of the HOMOs and LUMOs for n = 4–10 reveal that these orbitals are highly delocalized. By studying the projected density of states and molecular orbitals of Ag9S5− and Ag19S10− clusters, it is found that their molecular orbitals have superatomic properties. Superatomic properties play an important role in stabilizing clusters. Methods: This work used combined genetic algorithm and density functional theory (GA-DFT), and PBE0/Lanl2tz(Ag)/6-311G(d,p)(S) method to optimize the structures. Gaussian 16 program, Gauss view 6.0.16 program and Multiwfn 3.8 code are the softwares used. [ABSTRACT FROM AUTHOR]

The Cu-O-Cu core has been proposed as a potential site for methane oxidation in particulate methane monooxygenase. In this work, we used density functional theory (DFT) to design a mixed-valent Cu III -O-Cu II species from an experimentally known peroxo-dicopper complex supported by N-donor ligands containing phenolic groups. We found that the transfer of two-protons and two-electrons from phenolic groups to peroxo-dicopper core takes place, which results to the formation of a bis-μ-hydroxo-dicopper core. The bis-μ-hydroxo-dicopper core converts to a mixed-valent Cu III -O-Cu II core with the removal of a water molecule. The orbital and spin density analyses unravel the mixed-valent nature of Cu III -O-Cu II . We further investigated the reactivity of this mixed-valent core for aliphatic C-H hydroxylation. Our study unveiled that mixed-valent Cu III -O-Cu II core follows a hydrogen atom transfer mechanism for C-H activation. An in-situ generated water molecule plays an important role in C-H hydroxylation by acting as a proton transfer bridge between carbon and oxygen. Furthermore, to assess the relevance of a mixed-valent Cu III -O-Cu II core, we investigated aliphatic C-H activation by a symmetrical Cu II -O-Cu II core. DFT results show that the mixed-valent Cu III -O-Cu II core is more reactive toward the C-H bond than the symmetrical Cu II -O-Cu II core., (© 2024 Wiley-VCH GmbH.)