Intermolecular forces in van der waals dimers

1986 ◽  
Vol 29 (5) ◽  
pp. 1223-1239 ◽  
Author(s):  
G. J. B. Hurst ◽  
P. W. Fowler ◽  
A. J. Stone ◽  
A. D. Buckingham
Keyword(s):  
Van Der Waals ◽  
Intermolecular Forces

Dynamic pull-in instability of electrostatically actuated beams incorporating Casimir and van der Waals forces

2010 ◽  
Vol 224 (9) ◽  
pp. 2037-2047 ◽  
Author(s):  
M Moghimi Zand ◽  
M T Ahmadian
Keyword(s):  
Finite Element ◽  
Finite Element Model ◽  
Van Der Waals ◽  
Time Discretization ◽  
Element Model ◽  
Intermolecular Forces ◽  
Governing Equations ◽  
Electrostatically Actuated ◽  
Clamped Beams ◽  
Fringing Fields

In this study, influences of intermolecular forces on the dynamic pull-in instability of electrostatically actuated beams are investigated. The effects of midplane stretching, electrostatic actuation, fringing fields, and intermolecular forces are considered. The boundary conditions of the beams are clamped—free and clamped—clamped. A finite-element model is developed to discretize the governing equations, and Newmark time discretization is then employed to solve the discretized equations. The static pull-in instability is investigated to validate the model. Finally, dynamic pull-in instability of cantilevers and double-clamped beams are studied considering the Casimir and van der Waals effects. The results indicate that by increasing the Casimir and van der Waals effects, the effect of inertia on pull-in values considerably increases.

Molecular Level Characterization of Thin Paraffinic Films Using NEXAFS Spectroscopy

1993 ◽  
Vol 307 ◽  
Author(s):  
Paul A. Stevens ◽  
David J. Martella
Keyword(s):  
Thin Films ◽  
Phenyl Ring ◽  
Molecular Level ◽  
Van Der Waals ◽  
Intermolecular Forces ◽  
Native Oxide ◽  
X Ray ◽  
Nexafs Spectroscopy ◽  
Surface Normal ◽  
Repulsive Forces

ABSTRACTBecause near edge X-ray absorption fine structures (NEXAFS) are due to dipole transitions from core levels to unoccupied molecular orbitals, it is an ideal technique for obtaining molecular level information about the orientations of ordered species. Such information is important in assessing the relative importance of various intermolecular forces. For example in long chain molecules with bulky functional groups it is not clear a priori whether the attractive van der Waals forces will overcome the repulsive steric interactions to allow for ordering in thin films. To investigate this we have performed C-K edge NEXAFS spectroscopy studies of thin films of the paraffinic molecules C36H74 and (C18H37)2(NCO)C6H4CO2−+NH2(C18H37)2. The films were grown on a Si(111) surface covered with a native oxide. For the normal alkane, the spectra are dominated by three resolvable (Δhυ≈0.5 eV) features: one (C-H)* peak and two σ*(C-C) peaks. The polarization dependence of these peaks indicates that sub-250 Å C36H74 films have the chains of the molecules aligned along the surface normal. For ≈ 2000 Å films the molecular axes are inclined at angle of 32° with respect to the surface normal, in agreement with the crystalline structure determined by X-ray diffraction. In addition to the major structures of the alkane chains, the C-K NEXAFS of (C18H37)2(NCO)C6H4CO2−+NH2(C18H37)2 has a distinct π* peak due to the phenyl ring. Analysis of these resonances indicates that the C-C chains are also aligned along the surface normal, while the phenyl ring is inclined at an angle of 42° with respect to the normal. In conclusion NEXAFS spectroscopy has been used to show that, for the molecules studied, the attractive van der Waals interactions dominate the repulsive forces thus allowing the molecules to orient with their chains aligned along the surface normal in thin films formed on native oxide covered Si(111).

Non-additive intermolecular forces from the spectroscopy of van der Waals trimers: far-infrared spectra and calculations on Ar2-DCl

1994 ◽  
Vol 81 (3) ◽  
pp. 579-598 ◽  
Author(s):  
Matthew J. Elrod ◽  
Richard J. Saykally ◽  
Adam R. Cooper ◽  
Jeremy M. Hutson
Keyword(s):  
Infrared Spectra ◽  
Van Der Waals ◽  
Far Infrared ◽  
Intermolecular Forces ◽  
Far Infrared Spectra

Intermolecular forces and the properties of interacting molecules

1985 ◽  
Vol 63 (1) ◽  
pp. 30-33 ◽  
Author(s):  
A. D. Buckingham
Keyword(s):  
Hydrogen Bond ◽  
Ab Initio ◽  
Long Range ◽  
Van Der Waals ◽  
Intermolecular Forces ◽  
Electrostatic Forces ◽  
Van Der Waals Molecules ◽  
Range Theory ◽  
Ab Initio Computations ◽  
Isolated Molecules

Intermolecular forces, and their effects on the properties of gases, liquids, and solids, are related, by long-range theory, to the properties of the isolated molecules. The usefulness of this approach is expounded, and its limitations investigated by means of ab initio computations. It is suggested that the structures of many Van der Waals molecules, and particularly those with a hydrogen bond, are attributable to electrostatic forces.

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