查看更多>>摘要：The coordination structure and stability of the CuF species in acetonitrile solution was investigated by QM/MM, molecular dynamics and cluster-continuum methods. Different QM regions were used, such as CuF, CuF(CH3CN)(3) and CuF(CH3CN)(4). The use of the small QM region indicates a good stability of the CuF ion pair towards dissociation, with pentacoordinated Cu(I) in the CuF(CH3CN)(4) species. However, turning 4 acetonitrile molecules in the first solvation shell to the quantum mechanical level in the molecular dynamics simulation leads to the formation of tricoordinated Cu(I) ion, either Cu+(CH3CN)(3) or CuF(CH3CN)(2) species, indicating an easy dissociation of CuF in solution.
查看更多>>摘要：To canonic features of melting/freezing discontinuous phase transitions, one can encounter the lack of pre transitional effects in the liquids state and weak premelting effects with non-defined temperature evolutions in the crystalline state. This report shows the evidence for long-range and critical-like pretransitional effects in liquid menthol for electrooptic Kerr effect (EKE) and nonlinear dielectric effect (NDE). These methods are inherently associated with a strong electric field.The premelting effect, with well-defined temperature evolution, was evidenced in the crystalline state. Model explanations of these phenomena are proposed. For the premelting effect, the 'reversed' Mossotti-Catastrophe behavior is suggested.
查看更多>>摘要：This work employs the Particle-In-Cell method to evaluate the electron inverse bremsstrahlung absorption occurring in the interaction of laser and plasma under deep penetration welding conditions, with focus on the dependence of the inverse bremsstrahlung absorption coefficient on plasma and laser working parameters. When the laser intensity is small, about in the range of industrial applications, the inverse bremsstrahlung absorption coefficient is positively correlated with the electron density, coulomb logarithm and laser wavelength, and inversely correlated with electron temperature. When the laser intensity is high, the inverse bremsstrahlung absorption coefficient does not change significantly, regardless of plasma working parameters.
Li, PiyuKhan, Mohsin AliGalal, Ahmed M.Awan, Hamad Hassan...
15页
查看更多>>摘要：To encourage the consumption of crumb rubber (CR), gene expression programming (GEP) has been exercised in this paper to establish empirical models for estimation of mechanical properties of concrete made with NaOH treated CR. An extensive and reliable database of compressive strength of concrete made with NaOH treated CR is established through a comprehensive literature review. Literature review showed that compressive strength of NaOH treated CR concrete is affected by percentage of CR used as a replacement of sand (RS%), concentration of NaOH solution (NC in %), period of NaOH pre-treatment (PTP in hours), water to cement ratio (W/C), quantity of sand (S in kg/m(3)) and quantity of superplasticizer (SP in kg/m(3)). The performance of the established model is evaluated by doing parametric analysis, applying statistical checks and comparing with regression models. The R-values in the testing phase of GEP, linear and non-linear regression (LR and NLR) equations are 0.90 and 0.77 each respectively. Furthermore, objective function (OF) of GEP model is 25%, and 33% better than LR and NLR model. Thus, results reflected that the proposed GEP model is more accurate and possess a high generalization and prediction capability than LR and NLR equations with resolved overfitting issue. The results of this research can boost the re-usage of CR for expansion of green concrete leading to environmental safety and economic advantages.
查看更多>>摘要：The significance of aromatic amines as crude substances in diverse applications has attracted extensive consideration in the field of economic procedures for the reduction of nitroarenes. Also, the formation of Car-bon-Carbon bond as a dominant step in the structure of complex molecules is an important phenomenon in chemical reactions. Improvements of eco-friendly methodologies for reduction process and Carbon-Carbon bond formation have been noticeable. The present work represents through a capable heterogeneous Pd catalyst, the reduction of nitroarenes to the corresponding amines in the presence of N2H4 as a weak hydrogen donor reagent in the room temperature and solvent-free condition was progressed. In addition, several C-C bond formations through Suzuki-Miyaura reaction using one-pot mixture containing aryl halide, arylboronic acid in the presence of Pd catalyst at refluxed condition proceeded. Furthermore, the reusability of Pd catalyst for both reduction and Suzuki reactions showed five successive runs without any significant loss in its activity.
查看更多>>摘要：High level theoretical CCSD/cc-pVTZ calculations were carried out on 3-phospholene and its d1 derivative. These confirmed the microwave conclusion that the five-membered ring is puckered in the same direction as the PH group. The puckering angle was calculated to be 15.7. A one-dimensional potential energy function (PEF) for the ring-puckering motion was computed, and this confirmed that the PEF has a single minimum. A two-dimensional potential energy surface (PES) for the ring-puckering and P-H inversion motions was also computed, and this agreed very well with the published PES based on far-infrared spectra.
查看更多>>摘要：The structure, stability, electronic and thermochemical properties of small clusters of auro-acetylenes (C2Au2) are investigated using dispersion-corrected density functional theoretical (DFT) method. The studies showed that auro-acetylene clusters are connected mainly via C-Au center dot center dot center dot pi interactions analogous to C-H center dot center dot center dot pi interactions in acetylene clusters. In the most stable structures of trimer and tetramer, each of the constituent unit acts both as a C-Au center dot center dot center dot pi donor and as a C-Au center dot center dot center dot pi acceptor forming cyclic structures akin to acetylene clusters. The studies also revealed that the C-Au center dot center dot center dot pi interactions are stronger than the aurophilic interactions forming the clusters.
查看更多>>摘要：Herein, we used the time-dependent density functional theory to investigate the ESIPT process and fluorescence properties of 2-(2 '-Hydroxyaryl)benzazole (HBO) derivatives (1-3 compounds) by expanding the pi-conjugation framework. Calculated parameters show that the intramolecular hydrogen bond (Intra-HB) is enhanced in the excited state with the expansion of the pi-conjugation framework. Potential energy curves results also well prove that the weakened intra-HB is difficult to undergo the ESIPT process, which in turn controls the single-and dual-fluorescence emission. Exploring frontier molecular orbital, we clarify the intramolecular charge transfer is an important factor affecting the intra-HB strength.
查看更多>>摘要：Au-10(2+) has been found very stable showing a superatomic behavior with a highly symmetrical geometry and can be considered as the smallest copy of the golden pyramid Au20. In this work, we further explore superatomic clusters as analogues of more complex molecules by doping Au-10(2+)& nbsp;cluster with 3d transition metal atom. It is found that, in similarity to their sister Au19M, the structural evolution of Au9M2+ is ruled by the bond strength of AuM dimers and can be generalized into two motifs: the endohedrally doped cage-like structure for lighter dopants (M = Sc and Ti) and the slightly distorted tetrahedral structure for heavier ones. The average binding energies and dissociation energies are calculated to identify the relatively stable patterns. The molecular orbital (MO) diagram as well as the spin distribution are computed to understand the electronic structure and magnetic behavior of studied clusters. The spin magnetic moments of Au9M2+ clusters systematically vary from 0 to 5 mu B, depending on the localization of unpaired 3d electrons. With a large spin magnetic moment of 5 mu B, the exceptionally stable Au9M2+ is identified as a potential magnetic superatom and would be beneficial for further theoretical and experimental studies.
Kolesnikova, Inna N.Chegodaev, Nikolai A.Sharanov, Pavel Yu. F.Shishkov, IgorF...
6页
查看更多>>摘要：Conformational composition and molecule structure of gaseous picolinic acid hydrazide (picolinohydrazide) have been investigated for the first time by means of joint application of gas electron diffraction and quantum chemical calculations. Semi-experimental equilibrium molecular parameters of the prevailing conformer possessing C-s symmetry have been determined. The standard enthalpy of formation of gaseous picolinohydrazide has been estimated using G4 theory. The intermolecular interactions stabilizing major conformation of free picolinohydrazide have been discussed using the results of NBO, AIM and NCI analyses. The structure of gaseous picolinohydrazide was found to be different from that of the solid phase.
NSTL
Elsevier