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31.
Pu Wenjing Xi Xuyao Tao Pengyu Shi Bo Wen Jiaqi Lu Wei 《Journal of Radioanalytical and Nuclear Chemistry》2022,331(8):3295-3301
Journal of Radioanalytical and Nuclear Chemistry - Polysilane is expected to be a highly efficient and environmentally friendly liquid scintillator, for its unique fluorescence performance based on... 相似文献
32.
Piquemal JP Perera L Cisneros GA Ren P Pedersen LG Darden TA 《The Journal of chemical physics》2006,125(5):054511
Molecular dynamics simulations were performed using a modified amoeba force field to determine hydration and dynamical properties of the divalent cations Ca2+ and Mg2+. The extension of amoeba to divalent cations required the introduction of a cation specific parametrization. To accomplish this, the Thole polarization damping model parametrization was modified based on the ab initio polarization energy computed by a constrained space orbital variation energy decomposition scheme. Excellent agreement has been found with condensed phase experimental results using parameters derived from gas phase ab initio calculations. Additionally, we have observed that the coordination of the calcium cation is influenced by the size of the periodic water box, a recurrent issue in first principles molecular dynamics studies. 相似文献
33.
Jiao D King C Grossfield A Darden TA Ren P 《The journal of physical chemistry. B》2006,110(37):18553-18559
The alkaline earth metals calcium and magnesium are critically involved in many biomolecular processes. To understand the hydration thermodynamics of these ions, we have performed molecular dynamics simulations using a polarizable potential. Particle-mesh Ewald for point multipoles has been applied to the calculation of electrostatic interactions. The parameters in this model have been determined from an ab initio quantum mechanical calculation of dimer interactions between ions and water. Two methods for ion solvation free energy calculation, free energy perturbation, and the Bennett acceptance ratio have been compared. Both predict results consistent with other theoretical estimations while the Bennett approach leads to a much smaller statistical error. Based on the Born theory and the ion-oxygen radial distribution functions, we estimate the effective size of the ions in solution, concluding that K(+) > Na(+) congruent with Ca(2+) > Mg(2+). There appears to be much stronger perturbation in water structure, dynamics, and dipole moment around the divalent cations than the monovalent K(+) and Na(+). The average water coordination numbers for Ca(2+) and Mg(2+) are 7.3 and 6, respectively. The lifetime of water molecules in the first solvation shell of Mg(2+) is on the order of hundreds of picoseconds, in contrast to only few picoseconds for Ca(2+), K(+), or Na(+). 相似文献
34.
Yang G Han X Zhang W Liu X Yang P Zhou Y Bao X 《The journal of physical chemistry. B》2005,109(39):18690-18698
Variable-temperature NMR experiments and ab initio density functional calculations were carried out to investigate the conformation interconversion of novel chiral 3-alkyl-3,4-dihydro-2H-benzo[1,4]oxazine derivatives. With CDCl3 as the solvent, the coalescence temperatures of H2, H3, H11, and H19 of product 1 are about 289, 304, 292, and 316 K, with the corresponding activation free energies at 58.0 +/- 6.7, 60.9 +/- 7.1, 58.3 +/- 6.8, and 59.6 +/- 6.9 kJ.mol(-1), respectively. When dimethyl sulfoxide (DMSO-d6) was used as the solvent, 1H and 13C NMR signals were completely assigned at 375 K. The effects of solvent and temperature were investigated through a polarizable continuum model. At each theoretical level (MP2 or B3LYP), the changing tendencies of the calculated activation free energies and interconversion rates agree well with those of the NMR results. In addition, the interconversion rate at each specified temperature was calculated to be about 1.5 times faster in DMSO-d6 than in CDCl3. Accordingly, we failed to observe the coalescence phenomena of H3 and H19 in DMSO-d6 by NMR measurements from 296 to 375 K. The substitution effect at the R1-R5 positions was considered using density functional calculations, with the activation barriers decreasing as follows: product 6 > 3 > 1 > 7 > 2. This sequence is consistent with that of the reaction heats, except for product 7, implying that the interconversion processes may be thermodynamically controlled. Surprisingly, the substituted groups near the acetyl group in product 2 and 7 do not elevate the activation barrier but, instead, lower it somewhat, with the possible reasons for this provided in the paper. 相似文献
35.
Thermodynamic measurements of the solvation of salts and electrolytes are relatively straightforward, but it is not possible to separate total solvation free energies into distinct cation and anion contributions without reference to an additional extrathermodynamic assumption. The present work attempts to resolve this difficulty using molecular dynamics simulations with the AMOEBA polarizable force field and perturbation techniques to directly compute absolute solvation free energies for potassium, sodium, and chloride ions in liquid water and formamide. Corresponding calculations are also performed with two widely used nonpolarizable force fields. The simulations with the polarizable force field accurately reproduce in vacuo quantum mechanical results, experimental ion-cluster solvation enthalpies, and experimental solvation free energies for whole salts, while the other force fields do not. The results indicate that calculations with a polarizable force field can capture the thermodynamics of ion solvation and that the solvation free energies of the individual ions differ by several kilocalories from commonly cited values. 相似文献
36.
Catalytic hydrodeoxygenation(HDO) is one of the most effective methods to upgrade the oxygencontaining compounds derived from coal tar to valuable hydrocarbons. Herein, an efficient bimetallic catalyst Pt1Ni4/MgO was prepared and applied in the HDO of dibenzofuran(DBF). High yield(95%) of the desired product bicyclohexane(BCH) was achieved at 240 °C and 1.2 MPa of H2. Superior catalytic performance could be ascribed to the “relay catalysis” of Pt sites and Ni sit... 相似文献
37.
Mohasan Muhammad Aqeel Anas Bin Lv Pengyu Yang Yantao Duan Huiling 《Acta Mechanica Sinica》2021,37(3):447-455
Acta Mechanica Sinica - In this work, we numerically study the impact of a water droplet onto a deep oil pool. Two fluids are immiscible and the viscosity of the pool liquid is changed... 相似文献
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Pengyu Gong Yi Zhou Hui Li Jie Zhang Yuying Wu Peiru Zheng Yanyan Jiang 《Molecules (Basel, Switzerland)》2022,27(19)
Graphene and its derivatives are frequently used in cancer therapy, and there has been widespread interest in improving the therapeutic efficiency of targeted drugs. In this paper, the geometrical structure and electronic effects of anastrozole(Anas), camptothecin(CPT), gefitinib (Gefi), and resveratrol (Res) on graphene and graphene oxide(GO) were investigated by density functional theory (DFT) calculations and molecular dynamics (MD) simulation. Meanwhile, we explored and compared the adsorption process between graphene/GO and four drug molecules, as well as the adsorption sites between carriers and payloads. In addition, we calculated the interaction forces between four drug molecules and graphene. We believe that this work will contribute to deepening the understanding of the loading behaviors of anticancer drugs onto nanomaterials and their interaction. 相似文献
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