47 research outputs found
Dynamics of shape fluctuations of quasi-spherical vesicles revisited
In this paper, the dynamics of spontaneous shape fluctuations of a single,
giant quasi-spherical vesicle formed of a single lipid species is revisited
theoretically. A coherent physical theory for the dynamics is developed based
on a number of fundamental principles and considerations and a systematic
formulation of the theory is also established. From the systematic theoretical
formulation, an analytical description of the dynamics of shape fluctuations of
quasi-spherical vesicles is derived. In particular, in developing the theory we
have made a new interpretation of some of the phenomenological constants in a
canonical continuum description of fluid lipid-bilayer membranes and shown the
consequences of this new interpretation in terms of the characteristics of the
dynamics of vesicle shape fluctuations. Moreover, we have used the systematic
formulation of our theory as a framework against which we have discussed the
previously existing theories and their discrepancies. Finally, we have made a
systematic prediction about the system-dependent characteristics of the
relaxation dynamics of shape fluctuations of quasi-spherical vesicles with a
view of experimental studies of the phenomenon and also discussed, based on our
theory, a recently published experimental work on the topic.Comment: 18 pages, 4 figure
Trends in Ab Initio Oxygen Reduction Reaction Energetics of LaBO3 (B = Mn, Fe, Co, and Ni) for Solid Oxide Fuel Cells
Trends of Ab Initio Oxygen Reduction Reaction Energetics of LaBO3 (B = Mn, Fe, Co, and Ni) for Solid Oxide Fuel Cells
Towards a working density-functional theory for polymers: First-principles determination of the polyethylene crystal structure
Equilibrium polyethylene crystal structure, cohesive energy, and elastic
constants are calculated by density-functional theory applied with a recently
proposed density functional (vdW-DF) for general geometries [Phys. Rev. Lett.
92, 246401 (2004)] and with a pseudopotential-planewave scheme. The vdW-DF with
its account for the long-ranged van der Waals interactions gives not only a
stabilized crystal structure but also values of the calculated lattice
parameters and elastic constants in quite good agreement with experimental
data, giving promise for successful application to a wider range of polymers.Comment: 4 pages, 3 figure
Nature and strength of bonding in a crystal of semiconducting nanotubes: van der Waals density functional calculations and analytical results
The dispersive interaction between nanotubes is investigated through ab
initio theory calculations and in an analytical approximation. A van der Waals
density functional (vdW-DF) [Phys. Rev. Lett. 92, 246401 (2004)] is used to
determine and compare the binding of a pair of nanotubes as well as in a
nanotube crystal. To analyze the interaction and determine the importance of
morphology, we furthermore compare results of our ab initio calculations with a
simple analytical result that we obtain for a pair of well-separated nanotubes.
In contrast to traditional density functional theory calculations, the vdW-DF
study predicts an intertube vdW bonding with a strength that is consistent with
recent observations for the interlayer binding in graphitics. It also produce a
nanotube wall-to-wall separation which is in very good agreement with
experiments. Moreover, we find that the vdW-DF result for the nanotube-crystal
binding energy can be approximated by a sum of nanotube-pair interactions when
these are calculated in vdW-DF. This observation suggests a framework for an
efficient implementation of quantum-physical modeling of the CNT bundling in
more general nanotube bundles, including nanotube yarn and rope structures.Comment: 10 pages, 4 figure
Influence of van der Waals forces on the adsorption structure of benzene on silicon studied using density functional theory
Two different adsorption configurations of benzene on the Si(001)-(2 x 1) surface, the tight-bridge and butterfly structures, were studied using density functional theory. Several exchange and correlation functionals were used, including the recently developed van der Waals density functional (vdW-DF), which accounts for the effect of van der Waals forces. In contrast to the Perdew-Burke-Ernzerhof (PBE), revPBE, and other generalized-gradient approximation functionals, the vdW-DF finds that, for most coverages, the adsorption energy of the butterfly structure is greater than that of the tight-bridge structure
Erratum: Influence of van der Waals forces on the adsorption structure of benzene on silicon studied using density functional theory (vol 77, art no 121404, 2008)
Erratum of original article: Karen Johnston, Jesper Kleis, Bengt I. Lundqvist, and Risto M. Nieminen, Influence of van der Waals forces on the adsorption structure of benzene on silicon studied using density functional theory, Phys. Rev. B 77, 121404 (2008)