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121.
122.
Godehard Sutmann 《Journal of Electroanalytical Chemistry》1998,450(2):1946
We have performed molecular dynamics computer simulations of water in homogeneous external electric fields which were varied in a wide range of field strengths. The dielectric response is found to be linear up to fields E0≈0.01 V/Å from where dielectric saturation effects become important. At fields of E0≈3 V/Å a phase transition into an ordered, ice-like structure is observed, which is stabilized through hydrogen-bonds. With an increasing external electric field, the frequency spectrum of the water dynamics shows a remarkable red shift of the intramolecular modes and a blue shift of the librational motions, where the frequency varies quadratically with the field strength. A simple analytical model is discussed which reproduces the observed behavior. 相似文献
123.
Michael A. Collins 《Theoretical chemistry accounts》2002,108(6):313-324
This paper reviews the construction of molecular potential-energy surfaces by an interpolation method which has been developed
over the last several years. The method uses ab initio quantum chemistry calculations of the molecular electronic energy in
an automated procedure to construct global potential- energy surfaces which can be used to simulate chemical reactions with
either classical or quantum dynamics. The methodology is explained and several applications are presented to illustrate the
approach.
Received: 22 February 2002 / Accepted: 2 May 2002 / Published online: 6 November 2002
Correspondence to: M. A. Collins e-mail: collins@rsc.anu.edu.au
Acknowledgements. The methods described in this overview are the result of collaborations with former members of my group, in particular with
Josef Ischtwan, Meredith Jordon, Keiran Thompson and Ryan Bettens. I am also indebted for inspiration gained from many discussions
with my colleagues Leo Radom and Donghui Zhang (National University of Singapore). This work has been supported by the Supercomputer
Facility of the Australian National University and the Australian Partnership for Advanced Computing. 相似文献
124.
用准经典轨线方法研究了处于振动激发态的硅原子团簇与硅原子团簇碰撞的反应动力学,计算表明,对于Si4+Si3反应,当反应物团簇处于振动激发态时,有利于生成更小团簇的碎片,而对生成Si6+Si及Si5+Si2的影响不大。 相似文献
125.
126.
127.
Eckhard Spohr Andrij Trokhymchuk Douglas Henderson 《Journal of Electroanalytical Chemistry》1998,450(2):211
We report molecular dynamics (MD) simulations on the adsorption of water in attractive and repulsive slit pores, where the slit and a bulk region are in contact with each other. Water structure, surface force and adsorption behavior are investigated as a function of the overall density in the bulk region. The gas–liquid transition in both types of pores occurs at similar densities of the bulk region. 相似文献
128.
We employ dissipative particle dynamics (DPD) to examine the self‐assembly behavior of A2‐star‐(B‐alt‐C) molecules. We successfully observe various types of hierarchical structure‐within‐structures, such as A‐formed spheres in the matrix formed by B and C alternating layers, hexagonally packed A‐formed cylinders in the matrix with B and C segregated layers, B and C alternating layers‐within‐lamellae, coaxial B and C alternating domains within hexagonally packed BC‐formed cylinders in the A‐matrix, and co‐centric BC‐alternating domains within BC‐formed spheres in the A‐matrix, by increasing the A composition. Generally speaking, the small length‐scale B and C segregated domains are in parallel to the large length‐scale structures. This hierarchical periodicity along the same axis as well as the various characteristic structures, that the A2‐star‐(B‐alt‐C) copolymers display, are quite different from those in A‐block‐(B‐graft‐C) coil‐comb copolymers. Moreover, it is interesting to find that when the copolymer chain length increases, though the hierarchical structure type is maintained, the number of small length‐scale lamellae that can form within the large length‐scale structure increases. These hierarchical structures under various compositions are reported theoretically for the first time in the copolymer systems consisting of the alternating blocks, and are in good agreement with the most recent experimental work by Matsushita and co‐workers (Macromolecules 2007 , 40, 4023). 相似文献
129.
The intermolecular potential function of Smith–Thakkar type for C60 has been proposed, and its expression is as followsThe unit of u(r) is J/mol, r is the distance between two C60 molecules center and the unit is nm. Some properties of C60 in the gas and crystal have been studied using the interaction potential of Smith–Thakkar type, such as stability of C60 crystals, virial coefficient and lattice dynamics. 相似文献
130.
Theoretical study of the effect of frit quality on chromatography using computational fluid dynamics
Summary Frits at both ends of a chromatographic column, especially for a preparative column, have significant influence on the flow
distribution within the column and thus the column efficiency. However, frits have received little attention from chromatographers
in the past. Here a theoretical study was conducted with the aid of CFD software FLUENT to investigate the effect of frits
on the performance of homogeneous and heterogeneous chromatographic columns. A dimensionless number,FQ, was applied to characterize frit quality. This study visualized how frit quality affects the flow distribution and the concentration
band, the shape of eluted pulse at the colum exit and column efficiency. Simulation results show that the development length
of the flow distribution is related toFQ but has nothing to do with the packing heterogeneity. The curvature of the concentration band in a column depends onFQ and packing quality. This study shows column efficiency can be improved significantly by increasingFQ and/or frit permeability. 相似文献