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Efficient “On‐the‐Fly” calculation of Raman Spectra from Ab‐Initio molecular dynamics: Application to hydrophobic/hydrophilic solutes in bulk water 下载免费PDF全文
We present a novel computational method to accurately calculate Raman spectra from first principles. Together with an extension of the second‐generation Car‐Parrinello method of Kühne et al. (Phys. Rev. Lett. 2007, 98, 066401) to propagate maximally localized Wannier functions together with the nuclei, a speed‐up of one order of magnitude can be observed. This scheme thus allows to routinely calculate finite‐temperature Raman spectra “on‐the‐fly” by means of ab‐initio molecular dynamics simulations. To demonstrate the predictive power of this approach we investigate the effect of hydrophobic and hydrophilic solutes in water solution on the infrared and Raman spectra. © 2015 Wiley Periodicals, Inc. 相似文献
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Studies on polyethylene glycol/polyethersulfone composite membranes for FCC gasoline desulphurization by pervaporation 总被引:1,自引:0,他引:1
Ying Kong Ligang Lin Fuwei Lu Rongkun Liu Shuai Shao Deqing Shi 《European Polymer Journal》2008,44(10):3335-3343
A polyethylene glycol (PEG)/polyethersulfone (PES) composite membrane that can be applied on a commercial (or scale up) plant for fluid catalytic cracking (FCC) gasoline desulphurization was prepared through pre-wetting combined with double-layer coating methodology. Preparation methodology, morphologies characterization and performance test for the composite membranes were conducted. The results indicated that the pre-wetting method effectively confined the intrusion of PEG solution to porous PES support layer in coating process. The composite membrane had a clear-cut boundary surface between the dense active layer and the porous support layer, which was examined by scanning electron microscope (SEM). Pervaporation (PV) experiments indicated that the membrane, with the crosslinking agent amount of 17% and solids content in active layer solution of 16%, had a stable performance for FCC desulphurization. The sulphur enrichment factor came to 3.63, and the total permeation flux was 3.37 kg/m2 h. It was found that the PV performance of the composite membrane changed slightly when the thickness of active layer varied from 4.25 μm to 33.26 μm. 相似文献
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Composite solid electrolytes in the system (1 − x)LiNO3-xAl2O3, with x = 0.0-0.5 were synthesized by sol-gel method. The synthesis carried out at low temperature resulted in voluminous and fluffy products. The obtained materials were characterized by X-ray diffraction, differential scanning calorimetry, scanning electron microscopy/energy dispersive X-ray, Fourier transform infrared spectroscopy and AC impedance spectroscopy. Structural analysis of the samples showed base centred cell type of point lattice of LiNO3 for the composite samples with x = 0.1-0.2 and body centred cell for the sample with x = 0.3. A trace amount of α-LiAlO2 crystal phase was also present in these composite samples. The thermal analysis showed that the samples were in a stable phase between 48 °C and 230-260 °C. Morphological analysis indicated the presence of amorphous phase and particles with sizes ranging from micro to nanometre scale for the composite sample with x = 0.1. The conductivities of the composites were in the order of 10−3 and 10−2 S cm−1 at room temperature and 150 °C, respectively. 相似文献
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《Arabian Journal of Chemistry》2020,13(1):404-415
This work describes newly synthesized composite polymeric membranes and their utilization in propane/propylene separation in a gas mixture. The nonporous composite polymers were successfully synthesized by using thermoplastic polyurethane (TPU) and several silver salts/silver salts with ionic liquids (ILs). Our studies showed that silver bis(trifluoromethanesulfonyl)imide (Ag[Tf2N]) containing membranes outperformed other silver salt containing membranes in terms of selectivity. In addition, to this finding, ILs, as additives for the membranes, enhanced the selectivity by facilitating improved coordination of the olefin with the silver ions in the dense composite polymers. 相似文献
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The composite material of polyaniline/NiO/sodium dodecylbenzenesulfonate (SDBS) is synthesized in SDBS micelles. The composite material has satisfactory conductivity and thermostability, and the particle length, width, and thickness are about 200–500 m, 3–5 m, and 40–96 nm, respectively. 相似文献
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This paper reports proton and methanol transport behavior of composite membranes prepared for use in the direct methanol fuel cell (DMFC). The composite membranes were prepared by embedding various proportions (10–30 wt.%) of inorganic proton conducting material (tungstophosphoric acid (TPA)/MCM-41) into sulfonated poly(ether ether ketone) (SPEEK) polymer matrix. The results indicate that the proton conductivity of the membranes increases with increasing loading of solid proton conducting material. The highest conductivity value of 2.75 mS/cm was obtained for the SPEEK composite membrane containing 30 wt.% solid proton conducting material (50 wt.% TPA in MCM-41). The methanol permeability and crossover flux were also found to increase with increasing loading of the solid proton conducting material. Lowest permeability value of 5.7 × 10−9 cm2 s−1 was obtained for composite membrane with 10 wt.% of the solid proton conducting material (40 wt.% TPA in MCM-41). However, all the composite membranes showed higher selectivity (ratio between the proton conductivity and the methanol permeability) compared to the pure SPEEK membrane. In addition, the membranes are thermally stable up to 160 °C. Thus, these membranes have potential to be considered for use in direct methanol fuel cell. 相似文献
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György G. Ferenczy 《Journal of computational chemistry》2013,34(10):862-869
The application of the local basis equation (Ferenczy and Adams, J. Chem. Phys. 2009 , 130, 134108) in mixed quantum mechanics/molecular mechanics (QM/MM) and quantum mechanics/quantum mechanics (QM/QM) methods is investigated. This equation is suitable to derive local basis nonorthogonal orbitals that minimize the energy of the system and it exhibits good convergence properties in a self‐consistent field solution. These features make the equation appropriate to be used in mixed QM/MM and QM/QM methods to optimize orbitals in the field of frozen localized orbitals connecting the subsystems. Calculations performed for several properties in divers systems show that the method is robust with various choices of the frozen orbitals and frontier atom properties. With appropriate basis set assignment, it gives results equivalent with those of a related approach [G. G. Ferenczy previous paper in this issue] using the Huzinaga equation. Thus, the local basis equation can be used in mixed QM/MM methods with small size quantum subsystems to calculate properties in good agreement with reference Hartree–Fock–Roothaan results. It is shown that bond charges are not necessary when the local basis equation is applied, although they are required for the self‐consistent field solution of the Huzinaga equation based method. Conversely, the deformation of the wave‐function near to the boundary is observed without bond charges and this has a significant effect on deprotonation energies but a less pronounced effect when the total charge of the system is conserved. The local basis equation can also be used to define a two layer quantum system with nonorthogonal localized orbitals surrounding the central delocalized quantum subsystem. © 2013 Wiley Periodicals, Inc. 相似文献
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Micron-sized, monodisperse polystyrene (PS)/poly(n-butyl methacrylate) (PBMA) (2/1 w/w) composite particles having different morphologies were prepared by the solvent-absorbing/releasing method (SARM). There was an obvious influence of the releasing rate of toluene from the toluene-swollen composite particles on the reconstructed morphology by the SARM. In the case of fast release, the reconstructed morphology was a bicontinuous structure that is similar to that formed by spinodal decomposition. On the other hand, in the case of slow release, a hemispherical structure was formed that consisted of PS and PBMA phases.Part CCLIV of the series Studies on Suspension and Emulsion 相似文献
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Chitosan/PTFE composite membranes were prepared from casting a γ-(glycidyloxypropyl)trimethoxysilane (GPTMS)-containing chitosan solution on poly(styrene sulfuric acid) grafted expended poly(tetrafluoroethylene) film surface. The adhesion between the chitosan skin layer and the PTFE substrate was pretty good to warrant the high performance of chitosan/PTFE composite membranes using in pervaporation dehydration processes on isopropanol. The chitosan/PTFE membrane exhibited a permeation flux of 1730 g/m2 h and a separation factor of 775 at 70 °C on pervaporation dehydration of a 70 wt% isopropanol aqueous solution. The membrane also survived after a long-term operation test in 45 days. 相似文献
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Production of micron-sized monodispersed core/shell composite polymer particles by seeded dispersion polymerization 总被引:1,自引:0,他引:1
The effect of the weight ratio of seed polymer/monomer on the morphology of the poly(methyl methacrylate) (PMMA)/polystyrene
(PS) monodispersed composite particles produced by batch seeded dispersion polymerization of styrene with 1.64-μm-sized monodispersed
PMMA seed particles in a methanol/water medium (4/1 w/w) was examined. In the PMMA/PS weight ratios of 3/1 and 2/1, the composite
particles had a clear morphology consisting of a PMMA core and a PS shell. In the ratio of 1/1, a lot of small PS domains
were observed in the PMMA core though the PS shell was still formed. By stepwise addition of styrene monomer, the formation
of the small PS domain was depressed and complete core/shell morphology was formed. Absorption/release treatments of toluene
into/from the PMMA/PS (1/1 w/w) composite particles resulted in a drastic morphological change from the core/shell structure
to a multi- layered one.
Received: 2 February 1999 Accepted in revised form: 7 April 相似文献
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Fine particle superacidic sulfated zirconia (SO42−/ZrO2, S-ZrO2) was synthesized by ameliorated method, and composite membranes with different S-ZrO2 contents were prepared by a recasting procedure from a suspension of S-ZrO2 powder and Nafion solution. The physico-chemical properties of the membranes were studied by ion exchange capacity (IEC) and liquid water uptake measurements, scanning electron microscopy (SEM) and X-ray diffraction (XRD) analysis, thermogravimetry–mass spectrometry (TG–MS) and Fourier transform infrared (FT-IR) spectroscopy. The results showed that the IEC of composite membrane increased with the content of S-ZrO2, S-ZrO2 was compatible with the Nafion matrix, the incorporation of the S-ZrO2 could increase the crystallinity and also improve the initial degradation temperature of the composite membrane. The performance of single cell was the best when the S-ZrO2 content was 15 wt.%, and achieved 1.35 W/cm2 at 80 °C and 0.99 W/cm2 at 120 °C based on H2/O2 and at a pressure of 2 atm, the performance of the single cell with optimized S-ZrO2 was far more than that of the Nafion at the same condition (e.g. 1.28 W/cm2 at 80 °C, 0.75 W/cm2 at 120 °C). The 15 wt.% S-ZrO2/Nafion composite membrane showed lower fuel cell internal resistance than Nafion membranes at high temperature and low relative humidity (RH). 相似文献
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Monika Osińska Mariusz Walkowiak Aldona Zalewska Teofil Jesionowski 《Journal of membrane science》2009
The presented contribution aims at reconsidering the role of filler in affecting the ionic transport in composite gel electrolytes for Li-ion cells based on microporous polymer membranes. The gels have been prepared by swelling thin PVdF/HFP membranes either with conventional liquid electrolyte or with pure propylene carbonate solvent. The membranes contained dispersed submicron-size modified silica filler added in a wide range of weight ratios. The effect of filler content on the kinetics of liquid phase absorption and evaporation from the composite membranes, as well as on the conductivity of the corresponding gel electrolytes, has been studied and discussed in terms of the “colloidal” and “soggy sand” electrolyte concepts. It has been found that conductivity increase of composite gels is not directly correlated with the liquid electrolyte uptake. On this basis it is concluded that important part of ionic transport in this type of composite gel polymer electrolytes is realized on the filler grain boundaries, through overlapping space charge layers of the silica grains. 相似文献
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Electroless Pd and Ag deposition kinetics of the composite Pd and Pd/Ag membranes synthesized from agitated plating baths 总被引:1,自引:0,他引:1
The atomic absorption spectroscopy (AAS) has been successfully utilized for the measurement of the Pd and Ag ion concentrations in the plating baths and to elucidate the effects of temperature, initial metal ion and reducing agent concentrations and agitation on the electroless plating kinetics of Pd and Ag metals. The initial metal ion concentrations for Pd and Ag were varied over a range of 8.2–24.5 mM and 3.1–12.5 mM, respectively. The plating reactions were conducted in a constant temperature electroless plating bath over a temperature range of 20–60 °C and an initial hydrazine concentration range of 1.8–5.4 mM. It was found that the electroless plating of both Pd and Ag were strongly affected by the external mass transfer in the absence of bath agitation. The external mass transfer limitations for both Pd and Ag deposition have been minimized at or above an agitation rate of 400 rpm, resulting in a maximum conversion of the plating reaction at 60 °C and dramatically shortened plating times with the added advantage of uniform deposition morphology. The derivation of the differential rate laws and the estimation of the reaction orders and the activation energies for the electroless Pd and Ag kinetics were conducted via non-linear regression analysis based on the method of initial rates. For a constant-volume batch reactor, the integrated rate law was solved to calculate the conversion and the reactant concentrations as a function of plating time. The model fits were in good agreement with the experimental data. Furthermore, the bath agitation and the plating conditions used in the kinetics study were adopted for the synthesis of 16–20 μm thick composite Pd/Ag membranes (10–12 wt% Ag) and a pure-Pd membrane with a hydrogen selective dense Pd layer as thin as 4.7 μm. While hydrogen permeance of the Pd/Ag membranes A and B at 450 °C were 28 and 32 m3/m2-h-atm0.5, the H2 permeance for the 4.7 μm thick pure-Pd membrane at 400 °C was as high as 63 m3/m2-h-atm0.5. The long-term permeance testing of all the membranes synthesized from agitated plating baths resulted in a relatively slow leak growth due primarily to the improved morphology obtained via the bath agitation and modified plating conditions. 相似文献
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The simultaneous determination of several odorous trichlorobromophenols in water has been carried out by an in-sample derivatization
headspace solid-phase microextraction method (HS-SPME).The analytical procedure involved their derivatization to methyl ethers
with dimethyl sulfate/NaOH and further HS-SPME and gas chromatography-mass spectrometry (GC/MS) determination. Parameters
affecting both the derivatization efficiency and headspace SPME procedures, such as the selection of the SPME fiber coating,
derivatization–extraction time and temperature, were studied. The commercially available polydimethylsiloxane (PDMS) 100 μm
and Carboxen-polydimethylsiloxane-divinylbenzene (CAR-PDMS-DVB) fibers appeared to be the most suitable for the simultaneous
determination of these compounds. The precision of the HS-SPME/GC/MS method gave good relative standard deviations (RSDs)
run-to-run between 9% and 19% for most of them, except for 2,5-diCl-6-Br-phenol, 2,6-diCl-3-Br-phenol and-2,3,6-triBr-phenol
(22%, 25% and 23%, respectively). The method was linear over two orders of magnitude, and detection limits were compound dependent
but ranged from 0.22 ng/l to 0.95 ng/l. The results obtained for water samples using the proposed SPME procedure were compared
with those found with the EPA 625 method, and good agreement was achieved. Therefore, the in-sample derivatization HS-SPME/GC/MS
procedure here proposed is a suitable method for the simultaneous determination of odorous trichlorobromophenols in water. 相似文献
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Kyung Min Do Haldorai Yuvaraj Min Hee Woo Hyun Gyu Kim Euh Duck Jeong Keith P. Johnston Kwon Taek Lim 《Colloid and polymer science》2008,286(11):1343-1348
A novel synthetic route to prepare polystyrene/SiO2 composite microparticles in supercritical carbon dioxide (scCO2) is presented. Silica particles with the size of 130 nm which were surface-modified with 3-(trimethoxysilyl) propyl methacrylate
were used as seeds in the dispersion polymerization of styrene in the presence of a polymeric stabilizer, poly(1,1-dihydroheptafluorobutyl
methacrylate-co-diisopropylaminoethyl methacrylate) to produce dry composite particles. The transmission electron microscopy analysis revealed
that the composite microspheres contained several silica particles. 相似文献