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1.
在得到MP4, SCF的关于总能量及结合能的四个势能面的基础上,着重分析了电子相关作用, 消除基函数超位误差的Counterpoise(CP)技术对van der Waals配合物He-H2O的平衡几何的影响并得到了更精确的平衡几何预测。  相似文献   

2.
基态H2O+分子离子是重要的星际反应中间体.用MRCISD/cc-pVTZ先计算H2O+势能面,然后拟合成多体势能函数.全域势能面能很好地描述基态H2O+的行为.与两条反应通道的实验能变和其构型翻转反应能垒比较,表明计算结果与实验值相符.对计算点完成了力场的多项式拟合,对其振动模式进行了分析  相似文献   

3.
    
In the present work, high temperature oxidation of HP40 alloy was carried out at 1050 °C under H2–H2O and air atmospheres; the influence of atmosphere on surface morphology and composition was studied. Octahedral crystals with considerable spalled regions are present on the surface of alloy oxidized under air, the oxide scale composes of MnCr2O4, Cr2O3 and (Fe, Ni)Cr2O4 and spalled regions exhibit base alloy and SiO2‐rich regions. The surface of alloy oxidized under H2–H2O is fully covered by small granular crystals and blade‐type structures without spallation, and the oxide scale composes of MnCr2O4 and Cr2O3. Moreover, X‐ray photoelectron spectroscopy analysis shows considerable difference in chemical valence states of Mn, Cr and O elements on both alloy surfaces, and hydroxyl compounds exist on the alloy oxidized under H2–H2O atmosphere. Copyright © 2017 John Wiley & Sons, Ltd.  相似文献   

4.
CO2势能面和振动激发态的理论研究   总被引：1，自引：1，他引：0  
采用振动自洽场-组态相互作用(SCF-CI)方法通过实验振动光谱优化了CO2分子的势能函数,由该势能函数计算得到的纯振动光谱数据与实验值相比,所有能级的误差均在4cm-1以内,均方根偏差为1.50cm-1,所预测的Π态振转光谱也与实验值很接近.  相似文献   

5.
    
This article is an account and extension of a series of recent investigations, which using extensive quantum chemical methods provide analytical hyperspherical representations of the potential energy surfaces for the interactions of rare gases with H2S as a rigid molecule, and H2S2, considered as a floppy molecule with respect to torsional mode. For the H2S‐rare gas systems, the representation is based on a minimal model, here introduced and discussed. For H2S2, the study of the interaction with Xe, not considered previously, completes the series. The results are discussed with reference to the properties and trends expected for interactions of van der Waals type. © 2011 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

6.
    
We present the minimum‐energy structures and energetics of clusters of the linear N2O molecule with small numbers of para‐hydrogen molecules with pairwise additive potentials. Interaction energies of (p‐H2)–N2O and (p‐H2)–(p‐H2) complexes were calculated by averaging the corresponding full‐dimensional potentials over the H2 angular coordinates. The averaged (p‐H2)–N2O potential has three minima corresponding to the T‐shaped and the linear (p‐H2)–ONN and (p‐H2)–NNO structures. Optimization of the minimum‐energy structures was performed using a Genetic Algorithm. It was found that p‐H2 molecules fill three solvation rings around the N2O axis, each of them containing up to five p‐H2 molecules, followed by accumulation of two p‐H2 molecules at the oxygen and nitrogen ends. The first solvation shell is completed at N = 17. The calculated chemical potential oscillates with cluster size up to the completed first solvation shell. These results are consistent with the available experimental measurements. © 2009 Wiley Periodicals, Inc. J Comput Chem, 2009  相似文献   

7.
As part of our investigation of intramolecular hydrogen bonding and its geometrical consequences, ab initio molecular orbital calculations on 2-trifluoromethylphenol and 2-trifluoromethylvinyl alcohol and their parent structures were performed at the MP2/6–31+G** level of theory. The intramolecular hydrogen bonding in 2-trifluoromethylvinyl alcohol appears stronger than that in 2-trifluoromethylphenol as witnessed by the shorter F...H interaction (1.96 Å) and the greater bond length changes in the rest of the molecule, as compared with the respective parent molecules. Beyond the geometrical characteristics, the energetics of hypothetical isodesmic reactions and the small shift of the O(SINGLE BOND)H stretching frequency indicate that these C(SINGLE BOND)F...H(SINGLE BOND)O interactions are rather weak. © 1997 John Wiley & Sons, Inc. Int J Quant Chem 62: 645–652, 1997  相似文献   

8.
    
In the course of investigations relating to magnesia oxysulfate cement the basic magnesium salt hydrate 3Mg(OH)2 · MgSO4 · 8H2O (3–1–8 phase) was found as a metastable phase in the system Mg(OH)2‐MgSO4‐H2O at room temperature (the 5–1–2 phase is the stable phase) and was characterized by thermal analysis, Raman spectroscopy, and X‐ray powder diffraction. The complex crystal structure of the 3–1–8 phase was determined from high resolution laboratory X‐ray powder diffraction data [space group C2/c, Z = 4, a = 7.8956(1) Å, b = 9.8302(2) Å, c = 20.1769(2) Å, β = 96.2147(16)°, and V = 1556.84(4) Å3]. In the crystal structure of the 3–1–8 phase, parallel double chains of edge‐linked distorted Mg(OH2)2(OH)4 octahedra run along [–110] and [110] direction forming a pattern of crossed rods. Isolated SO4 tetrahedra and interstitial water molecules separate the stacks of parallel double chains.  相似文献   

9.
    
Calculations are presented for the structure and the isomerization reaction of various conformers of the bare serine, neutral serine–(H2O)n and serine zwitterion–(H2O)n (n = 1, 2) clusters. The effects of binding water molecules on the relative stability and the isomerization processes are examined. Hydrogen bonding between serine and the water molecule(s) may significantly affect the relative stability of conformers of the neutral serine–(H2O)n (n = 1, 2) clusters. The sidechain (OH group) in serine is found to have a profound effect on the structure and isomerization of serine–(H2O)n (n = 1, 2) clusters. Conformers with the hydrogen bonding between water and the hydroxyl group of serine are predicted. A detailed analysis is presented of the isomerization (proton transfer) pathways between the neutral serine–(H2O)2 and serine zwitterion–(H2O)2 clusters by carrying out the intrinsic reaction coordinate analysis. At least two water molecules need to bind to produce the stable serine zwitterion–water cluster in the gas phase. The isomerization for the serine–(H2O)2 cluster proceeds by the concerted double and triple proton transfer mechanism occurring via the binding water molecules, or via the hydroxyl group. © 2004 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

10.
    
Previous research in our laboratory found that the absolute bioavailability of vitexin‐2′′‐O‐rhamnoside (VR) was quite low at 4.89%. A rapid and sensitive UHPLC method using hesperidin as an internal standard was therefore developed and validated to investigate the reasons for this by determining VR in rat plasma after administering intravenously, intraportally (5 mg/kg), intraduodenally and intragastrically (40 mg/kg) to the rat model of the hepatic, gastric and intestinal first‐pass effects. As only a high intestinal first‐pass effect of VR was found, that is, there existed a low bioavailability of VR (2.40%), inhibitors of P‐glycoprotein (P‐gp) and cytochrome P450 3A (CYP3A), including verapamil, cyclosporin A and midazolam, and absorption enhancers, including bile salts and borneol, combined with VR, were instilled into duodenum to evaluate the effects on bioavailability of VR. The results demonstrated that area under the concentration–time curve (AUC) values of VR slightly increased after administration of verapamil, cyclosporin A and midazolam, indicating that CYP3A and P‐gp do not play an important role in the first‐pass effect in the intestine. AUC values of VR significantly increased after administering bile salts or borneol, indicating that the low bioavailability of VR was mainly related to its poor absorption in the intestine. Copyright © 2015 John Wiley & Sons, Ltd.  相似文献   

11.
    
A long wavelength emission fluorescent (612 nm) chemosensor with high selectivity for H2PO4? ions was designed and synthesized according to the excited state intramolecular proton transfer (ESIPT). The sensor can exist in two tautomeric forms ('keto' and 'enol') in the presence of Fe3+ ion, Fe3+ may bind with the 'keto' form of the sensor. Furthermore, the in situ generated GY‐Fe3+ ensemble could recover the quenched fluorescence upon the addition of H2PO4? anion resulting in an off‐on‐type sensing with a detection limit of micromolar range in the same medium, and other anions, including F?, Cl?, Br?, I?, AcO?, HSO4?, ClO4? and CN? had nearly no influence on the probing behavior. The test strips based on 2‐[2‐hydroxy‐4‐(diethylamino) phenyl]‐1H‐imidazo[4,5‐b]phenazine and Fe3+ metal complex ( GY‐Fe3+ ) were fabricated, which could act as convenient and efficient H2PO4? test kits.  相似文献   

12.
We have presented the explicit formulas for first and second derivatives of A and B matrices, appearing in the random phase approximation (RPA), with the aid of Lagrangian technique. Owing to the 2n + 1 rule, the Lagrangian approach is more efficient than the conventional approach to evaluate the higher‐order matrix elements. We have confirmed the validity of our formulation by demonstrating the geometry optimization of the first‐excited singlet states of formaldehyde, ethylene, and 1‐amino‐3‐propenal molecules. © 2005 Wiley Periodicals, Inc. Int J Quantum Chem, 2005  相似文献   

13.
    
Among the different oxidants used for the preparation of polyaniline in the solid‐state, iron (III) chloride (FeCl3.6H2O) can act as both oxidant and dopant. This work reports the synthesis and characterization of novel composite of polyaniline/silica. The polymerization was performed by oxidative polymerization of aniline hydrochloride in the presence of silica and FeCl3.6H2O under solid‐state (solvent‐free) condition. The FeCl3.6H2O has been chemically supported on silica and generated silica‐supported FeCl3 ( SSFe ), which plays three important roles simultaneously (a) oxidant, (b) primary dopant, and (c) secondary dopant (Lewis acid). Furthermore, the existence of silica is important for proceeding of polymerization in solid state. In the other words, the surface polymerization and green chemistry in solid state have been coupled. The characterization and doping process are verified by ultraviolet‐visible, Fourier transform infrared, atomic absorption spectroscopy, thermogravimetric analysis, differential scanning calorimetry, and elemental analysis (CHNS). From atomic absorption spectroscopy the ratio of Fe/N in the composite obtained about 1, which confirms the formation of delocalized polarons by SSFe in the composites. The conductivity is in the range of semi‐conductive. Furthermore, contact resistance was determined by circular‐transmission line measurement. According to scanning electron microscopy images silica particles have been thoroughly coated by polyaniline within the range of 0.2 to 1 µm. However, transition electron microscopy images depict the uniform solid nanospheres (no hollow spheres or fibers), and their mean diameters are under of 50 nm. It confirms nanocomposite of core–shell PANI‐SSFe. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

14.
    
Excited states of fluorene‐ethylenedioxythiophene (FEDOT) and fluorene‐S,S‐dioxide‐thiophene (FTSO2) monomers and dimers were studied by the symmetry‐adapted cluster (SAC)‐configuration interaction (CI) method. The absorption and emission peaks observed in the experimental spectra were theoretically assigned. The first three excited states of the optimized conformers, and the conformers of several torsional angles, were computed by SAC‐CI/D95(d). Accurate absorption spectra were simulated by taking the thermal average for the conformers of torsional angles from 0° to 90°. The conformers of torsional angles 0°, 15°, and 30° mainly contributed to the absorption spectra. The full width at half‐maximum of the FEDOT absorption band is 0.60 eV (4839 cm?1), which agrees very well with the experimental value of 0.61 eV (4900 cm?1). The maximum absorption wavelength is located at 303 nm, which is close to those of the experimental band (327 nm). The calculated absorption spectrum of FTSO2 showed two bands in the range of 225–450 nm. This agrees very well with the available experimental spectrum of a polymer of FTSO2, where two bands are detected. The excited‐state geometries were investigated by CIS/6‐31G(d). These showed a quinoid‐type structure which exhibited a shortening of the inter‐ring distance (0.06 Å for FEDOT and 0.04 Å for FTSO2). The calculated emission energy of FEDOT is 3.43 eV, which agrees very well with the available experimental data (3.46 eV). The fwhmE is about 0.49 eV (3952 cm?1), while the experimental fwhm is 0.43 eV (3500 cm?1). For FTSO2, two bands were also found in the emission spectrum. © 2010 Wiley Periodicals, Inc. J Comput Chem, 2010  相似文献   

15.
    
The CASPT2 potential energy curves (PECs) for O‐loss dissociation from the X2Π, A2Π, B2Σ+, C2Σ+, 14Σ?, 12Σ?, and 14Π states of the OCS+ ion were calculated. The PEC calculations indicate that X2Π, 14Σ?, 12Σ?, and 14Π correlate with CS+(X2Σ+) + O(3Pg); A2Π and B2Σ+ correlate with CS+(A2Π) + O(3Pg); and C2Σ+ probably correlates with CS+(X2Σ+) + O(1Dg). The CASSCF minimum energy crossing point (MECP) calculations were performed for the C2Σ+/14Σ?, C2Σ+/14Π, A2Π/14Σ?, A2Π/12Σ?, A2Π/14Π, and B2Σ+/12Σ? state pairs and the spin‐obit couplings were calculated at the located MECPs. A conical intersection point between the B2Σ+ and C2Σ+ potential energy surfaces was found at the CASSCF level. Based on our calculations, seven O‐loss predissociation processes of the C2Σ+ state are suggested and an appearance potential value of 7.13 eV for the CS+ + O product group is predicted. © 2010 Wiley Periodicals, Inc. Int J Quantum Chem, 2011  相似文献   

16.
    
The cooperative enhancement of water binding to the antiparallel β‐sheet models has been studied by quantum chemical calculations at the MP2/6‐311++G**//MP2/6‐31G* level. The binding energies of the two antiparallel β‐sheet models consisting of two strands of diglypeptide are calculated by supermolecular approach. Then water molecules are gradually bonded to the diglypeptide by N? H···OH2 and C?O···HOH hydrogen bonds. Our calculation results indicated that the hydrogen bond length and the atom charge distribution are affected by the addition of H2O molecules. The binding energy of antiparallel diglypeptide β‐sheet models has a great improvement by the increasing of the hydrogen bond cooperativity and the more H2O molecules added the more cooperativity enhancement can be found. The orbital interactions are calculated by natural bond orbital analysis, and the results indicate that the cooperative enhancement is closely related to the orbital interaction. © 2012 Wiley Periodicals, Inc.  相似文献   

17.
    
A wealth of epidemiological evidence indicates a strong link between type 2 diabetes (T2D) and Alzheimer's disease (AD). The fiber deposition with cross‐β‐sheet structure formed by self‐aggregation and misfolding of amyloidogenic peptides is a common hallmark of both diseases. For the patients with T2D, the fibrils are mainly found in the islets of Langerhans that results from the accumulation of human islet amyloid polypeptide (hIAPP). The major component of aggregates located in the brain of AD patients is amyloid‐β (Aβ). Many biophysical and physiological properties are shared by hIAPP and Aβ, and both peptides show similar cytotoxic mechanisms. Therefore, it is meaningful to investigate the possible cross‐interactions of hIAPP and Aβ in both diseases. In this article, the segment 25–35 of Aβ was selected because Aβ25–35 was a core region in the process of amyloid formation and showed similar aggregation tendency and toxicity with full‐length Aβ. The electrospray ionization‐ion mobility‐mass spectrometry analysis and thioflavin T fluorescence kinetic analysis combined with transmission electron microscopy were used to explore the effects of the coexistence of Aβ25–35 and hIAPP on the self‐aggregation of both peptides and whether there was co‐assembly in fibrillation. The results indicated that the aggregation of hIAPP and Aβ25–35 had two nucleation stages in the binary mixtures. hIAPP and Aβ25–35 had a high binding affinity and a series of hetero‐oligomers formed in the mixtures of hIAPP and Aβ25–35 in the early stage. The cross‐reaction between hIAPP monomers and Aβ25–35 monomers as well as a little of oligomers during primary nucleation stage could accelerate the aggregation of Aβ25–35. However, owing to the obvious difference in aggregation ability between hIAPP and Aβ25–35, this cross‐interaction had no significant impact on the self‐assembly of hIAPP. Our study may offer a better understanding for exploring the molecular mechanism of the association between AD and T2D observed in clinical and epidemiological studies and developing therapeutic strategies against amyloid diseases.  相似文献   

18.
    
In order to obtain efficient basis sets for the evaluation of van der Waals complex intermolecular potentials, we carry out systematic basis set studies. For this, interaction energies at representative geometries on the potential energy surfaces are evaluated using the CCSD(T) correlation method and large polarized LPol‐n and augmented polarization‐consistent aug‐pc‐2 basis sets extended with different sets of midbond functions. On the basis of the root mean square errors calculated with respect to the values for the most accurate potentials available, basis sets are selected for fitting the corresponding interaction energies and getting analytical potentials. In this work, we study the Ne–N2 van der Waals complex and after the above procedure, the aug‐pc‐2–3321 and the LPol‐ds‐33221 basis set results are fitted. The obtained potentials are characterized by T‐shaped global minima at distances between the Ne atom and the N2 center of mass of 3.39 Å, with interaction energies of ?49.36 cm?1 for the aug‐pc‐2–3321 surface and ?50.28 cm?1 for the LPol‐ds‐33221 surface. Both sets of results are in excellent agreement with the reference surface. To check the potentials further microwave transition frequencies are calculated that agree well with the experimental and the aV5Z‐33221 values. The success of this study suggests that it is feasible to carry out similar accurate calculations of interaction energies and ro‐vibrational spectra at reduced cost for larger complexes than has been possible hitherto. © 2013 Wiley Periodicals, Inc.  相似文献   

19.
    
A rapid and sensitive LC–MS/MS method with good accuracy and precision was developed and validated for the pharmacokinetic study of quercetin‐3‐O‐β‐d ‐glucopyranosyl‐7‐O‐β‐d ‐gentiobioside (QGG) in Sprague–Dawley rats. Plasma samples were simply precipitated by methanol and then analyzed by LC–MS/MS. A Venusil® ASB C18 column (2.1 × 50 mm, i.d. 5 μm) was used for separation, with methanol–water (50:50, v/v) as the mobile phase at a flow rate of 300 μL/min. The optimized mass transition ion‐pairs (m/z) for quantitation were 787.3/301.3 for QGG, and 725.3/293.3 for internal standard. The linear range was 7.32–1830 ng/mL with an average correlation coefficient of 0.9992, and the limit of quantification was 7.32 ng/mL. The intra‐ and inter‐day precision and accuracy were less than ±15%. At low, medium and high quality control concentrations, the recovery and matrix effect of the analyte and IS were in the range of 89.06–92.43 and 88.58–97.62%, respectively. The method was applied for the pharmacokinetic study of QGG in Sprague–Dawley rats. Copyright © 2016 John Wiley & Sons, Ltd.  相似文献   

20.
    
Four new biphenyl derivatives, oblongifoliagarcinines A–D ( 1 – 4 ), were isolated on the chemical investigation of the stems and leaves of Garcinia oblongifolia. The structures of 1 – 4 were established on the basis of 1D‐ and 2D‐NMR and other spectroscopic analyses.  相似文献   

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